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The inner $\sim$200 pc region of the Galaxy contains a 4 million M$_{\odot}$ supermassive black hole (SMBH), significant quantities of molecular gas, and star formation and cosmic ray energy densities that are roughly two orders of magnitude higher than the corresponding levels in the Galactic disk. At a distance of only 8.2 kpc, the region presents astronomers with a unique opportunity to study a diverse range of energetic astrophysical phenomena, from stellar objects in extreme environments, to the SMBH and star-formation driven feedback processes that are known to influence the evolution of galaxies as a whole. We present a new survey of the Galactic center conducted with the South African MeerKAT radio telescope. Radio imaging offers a view that is unaffected by the large quantities of dust that obscure the region at other wavelengths, and a scene of striking complexity is revealed. We produce total intensity and spectral index mosaics of the region from 20 pointings (144 hours on-target in total), covering 6.5 square degrees with an angular resolution of 4$"$,at a central frequency of 1.28 GHz. Many new features are revealed for the first time due to a combination of MeerKAT's high sensitivity, exceptional $u,v$-plane coverage, and geographical vantage point. We highlight some initial survey results, including new supernova remnant candidates, many new non-thermal filament complexes, and enhanced views of the Radio Arc Bubble, Sgr A and Sgr B regions. This project is a SARAO public legacy survey, and the image products are made available with this article., Comment: 29 pages, 15 figures, 3 tables, accepted for publication in the The Astrophysical Journal. Replacement arXiv version with higher quality figures

MeerKAT's large number of antennas, spanning 8 km with a densely packed 1 km core, create a powerful instrument for wide-area surveys, with high sensitivity over a wide range of angular scales. The MeerKAT Galaxy Cluster Legacy Survey (MGCLS) is a programme of long-track MeerKAT L-band (900-1670 MHz) observations of 115 galaxy clusters, observed for $\sim$6-10 hours each in full polarisation. The first legacy product data release (DR1), made available with this paper, includes the MeerKAT visibilities, basic image cubes at $\sim$8" resolution, and enhanced spectral and polarisation image cubes at $\sim$8" and 15" resolutions. Typical sensitivities for the full-resolution MGCLS image products are $\sim$3-5 {\mu}Jy/beam. The basic cubes are full-field and span 4 deg^2. The enhanced products consist of the inner 1.44 deg^2 field of view, corrected for the primary beam. The survey is fully sensitive to structures up to $\sim$10' scales and the wide bandwidth allows spectral and Faraday rotation mapping. HI mapping at 209 kHz resolution can be done at $0, Comment: 43 pages, 33 figures, 6 tables. Accepted for publication in Astronomy and Astrophysics

Arizona is an important region of the USA for winter production of baby leaf crops such as spinach (Spinacia oleracea), table beet (Beta vulgaris subsp. vulgaris Condivita Group), and Swiss chard (B. vulgaris subsp. vulgaris Cicla Group). In the winter of 2019, severe leaf spots were observed at 80% incidence and 40% severity per plant in a 1-ha baby leaf Swiss chard crop of an (unknown cultivar) in Arizona. The lesions were circular to irregular, necrotic, water-soaked, and 1 to 5 mm in diameter. Symptomatic leaf sections (1-cm2) were surface-sterilized with 0.6% NaOCl, rinsed, and macerated in sterilized, deionized water. An aliquot of each macerate was streaked onto King's B (KB) agar medium. Cream-colored, non-fluorescent colonies typical of Pseudomonas were isolated consistently, and all were non-fluorescent. A dozen isolates selected randomly were all negative for potato soft rot, oxidase, and arginine dihydrolase, and positive for levan production and tobacco hypersensitivity, which is typical of fluorescent P. syringae isolates, but can also include non-fluorescent strains (Lelliot et al. 1966). Three isolates were tested for pathogenicity on the table beet cv. Red Ace and Swiss chard cv. Silverado. Strain Pap009 of P. syringae pv. aptata (Psa), demonstrated previously to be pathogenic on Swiss chard and table beet, served as a positive control strain (Derie et al. 2016; Safni et al. 2016). Each isolate was grown inoculated into medium 523 broth and incubated on a shaker at 175 rpm overnight at 25°C. Each bacterial suspension was adjusted to an optical density (OD) of 0.3 at 600 nm (108 CFU/ml), and diluted in 0.0125M phosphate buffer to 107 CFU/ml. Thirty-day-old seedlings grown in Redi-Earth Plug and Seedling Mix in a greenhouse at 22 to 26°C were inoculated by rubbing the abaxial and adaxial leaf surfaces of each plant with a cotton swab dipped in inoculum to which Carborundum had been added (0.06 g/10 ml). The negative control plants were treated similarly with phosphate buffer with Carborundum. The experiment was set up as a randomized complete block design with 4 replications per treatment and 6 seedlings per experimental unit. In both trials, leaf spots resembling those on the original plants developed on all table beet and Swiss chard plants inoculated with the Arizona isolates and Pap009, but not on negative control plants. Disease severity was greater on Swiss chard (average 39% leaf area with spots) than on table beet (14%). Re-isolates obtained from inoculated seedlings using the same method as the original isolations resembled Psa. Multilocus sequence analysis (MLSA) was carried out for the original three Arizona isolates and the re-isolates using DNA amplified from the housekeeping genes gyrB, rpoD, gapA, and gltA (Hwang et al. 2005; Sarkar and Guttman 2004). Sequence identities of these genes of the Arizona isolates (GenBank accession numbers MW291615 to MW291618 for strain Pap089; MW291619 to MW291622 for Pap095; and MW291623 to MW291626 for Pap096 for gltA, gyrB, rpoD, and gapA, respectively) and the re-isolates ranged from 98 to 100% with those of Psa pathotype strain CFBP 1617 in the PAMDB database (Almeida et al. 2010; Altschul et al. 1997). Based on Koch's postulates, colony characteristics, and MLSA, Psa was the causal agent of leaf spots in the Arizona Swiss chard crop. To our knowledge, this is the first report of bacterial leaf spot on chard in Arizona. The pathogen could have been introduced on infected seed as Psa is readily seedborne and seed transmitted.

The Galactic Centre contains a supermassive black hole with a mass of 4 million suns within an environment that differs markedly from that of the Galactic disk. While the black hole is essentially quiescent in the broader context of active galactic nuclei, X-ray observations have provided evidence for energetic outbursts from its surroundings. Also, while the levels of star formation in the Galactic Centre have been approximately constant over the last few hundred Myr, there is evidence of elevated short-duration bursts, strongly influenced by interaction of the black hole with the enhanced gas density present within the ring-like Central Molecular Zone at Galactic longitude |l| < 0.7 degrees and latitude |b| < 0.2 degrees. The inner 200 pc region is characterized by large amounts of warm molecular gas, a high cosmic ray ionization rate, unusual gas chemistry, enhanced synchrotron emission, and a multitude of radio-emitting magnetised filaments, the origin of which has not been established. Here we report radio imaging that reveals bipolar bubbles spanning 1 degree x 3 degrees (140 parsecs x 430 parsecs), extending above and below the Galactic plane and apparently associated with the Galactic Centre. The structure is edge-brightened and bounded, with symmetry implying creation by an energetic event in the Galactic Centre. We estimate the age of the bubbles to be a few million years, with a total energy of 7 x 10^52 ergs. We postulate that the progenitor event was a major contributor to the increased cosmic-ray density in the Galactic Centre, and is in turn the principal source of the relativistic particles required to power the synchrotron emission of the radio filaments within and in the vicinity of the bubble cavities., 25 pages, 3 figures, 3 tables, authors' version of a Letter published in Nature on 11 September 2019

In September 2000, symptoms typical of leaf spot caused by Cladosporium variabile were observed on a spinach (Spinacea oleracea L.) seed crop in western Washington. Dry, bleached spots (1 to 20 mm) were most abundant on lower leaves. Two isolates of C. variabile and three isolates of Stemphylium were recovered by plating surface-sterilized (0.1% sodium hypochlorite) sections of symptomatic leaf tissue onto water agar and acidified potato dextrose agar (PDA). Transfers of each isolate were made to PDA, and cultures were kept at 24 ± 2°C on a lab bench (natural day/night cycle) for 10 to 14 days. Spore suspensions (105/ml) of the isolates of C. variabile were prepared in a 0.01% solution of Tween 80. Isolates of Stemphylium produced few spores, so mycelial suspensions (105 fragments/ml) were prepared. Five 8-week-old seedlings of each of the cultivars Winter Bloomsdale and Ozarka II were inoculated per fungal isolate by atomizing the inoculum onto each seedling until all leaves were covered with a thin film of droplets (4 to 5 ml of inoculum per seedling). Plants were enclosed in plastic bags on a greenhouse bench (24 ± 3°C) for 72 h (8 h/16 h day/night). Symptoms developed within 80 h of inoculation for both isolates of C. variabile and two isolates of Stemphylium. Small (1 to 2 mm) sunken spots turned white 24 to 48 h later and became dry and bleached. Lesions caused by isolates of Stemphylium enlarged and coalesced more rapidly than lesions caused by C. variabile, and were more irregular and usually not delimited by the thin brown margin typical of lesions caused by C. variabile. The differences in symptoms were consistent on both spinach cultivars. Symptoms were not observed on non-inoculated control plants nor on plants inoculated with the third isolate of Stemphylium. C. variabile and Stemphylium were reisolated from symptomatic leaf tissue. Colony morphology, conidiophores, and conidia of the pathogenic Stemphylium isolates were similar to those of pathogenic isolates of Stemphylium botryosum obtained from spinach plants in California (2). This is the first report of S. botryosum as a foliar pathogen of spinach seed crops in Washington. Although Correll et al. (1) noted Stemphylium to be damaging on mature spinach plants grown for seed production, S. botryosum may not have been diagnosed previously on spinach seed crops in Washington because of the similarity of symptoms caused by S. botryosum and C. variabile. S. botryosum was recently reported as a foliar pathogen of spinach in California (2). References: (1) J. C. Correll et al. Plant Dis. 78:653, 1994. (2) S. T. Koike et al. Plant Dis. 85:126, 2001.

Fusarium oxysporum f. sp. cepae and an unidentified Fusarium species have been reported to cause bulb rot of onion (Allium cepa L.) in Washington (1). In August and September 2002, a salmon-pink discoloration was observed on the outer three to four layers of dry scales of approximately 20% of white onion bulbs of cv. Cometa F1, in each of two 20-acre fields in the Columbia Basin of central Washington. Isolations from the discolored areas of the dry scales onto water agar and potato dextrose agar (PDA) yielded fungal colonies characteristic of F. proliferatum (3). The isolates formed long, V-shaped chains of microconidia on polyphialides. Pathogenicity of the isolates of F. proliferatum was tested on white onion bulbs purchased at a local grocery store. The outermost dry scales of each bulb were removed, and the bulb was inoculated by one of three methods: (i) a 5-mm3 section of the fleshy scales was removed using a scalpel, the wound was filled with a 3-mm2 plug of PDA colonized by F. proliferatum, the plug was covered with the section of scale that had been removed, and the inoculation site was covered with Parafilm; (ii) the basal plate of the bulb was dipped into a suspension of 106 microconidia per ml; or (iii) the basal plate was dipped into the spore suspension after wounding by inserting a dissecting needle into the bulb to a depth of 1 cm. A noninoculated bulb provided a control treatment. Bulbs were incubated in a moist chamber at 13°C and examined for discoloration of the outer scales and development of bulb rot. After 2 weeks, salmon-pink discoloration of the outer scales was observed at the inoculation site for both methods of dip inoculation, but not for the plug inoculation method. After 3 weeks, water-soaked, tan to golden, shrunken, soft tissue was observed on the remainder of each dip inoculated bulb, but symptoms of basal rot did not develop. Symptoms were similar to those reported in Idaho for a bulb rot of stored onions caused by F. proliferatum (2). One of the nonwounded inoculated bulbs did not develop a bulb rot, but pinkish discoloration was observed beneath the outer scales and in the neck. F. proliferatum was reisolated from the inoculated bulb tissues. The discoloration observed on the white onions raised concern about the potential for infection to develop into bulb rot in storage. However, thorough curing of the bulbs immediately upon storage restricted infection to the outer dry scales. Similar symptoms were observed at harvest on the bulbs of other white onions in a cultivar trial located near Quincy, WA, although symptoms were not observed on yellow or red cultivars in the trial. The same symptoms were later observed on approximately 70% of bulbs harvested from a 32-acre fresh-market crop of the cv. Sterling in the Columbia Basin. These symptomatic bulbs were rejected for the fresh market. To our knowledge, this is the first report of infection of onion bulbs by F. proliferatum in Washington, which in 2001, had the third largest acreage of onions in the United States after California and Oregon (USDA National Agricultural Statistics Service). References: (1) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St. Paul, MN, 1989. (2) S. K. Mohan et al. (Abstr.) Phytopathology 87:S67, 1997. (3) P. E. Nelson et al. Fusarium species: An Illustrated Manual for Identification. The Pennsylvania State University Press, University Park, 1983.

Bacterial pathogens of onion (Allium cepa) plants and their undetected presence in seed can cause substantial losses to onion producers. In this study, 23 Pseudomonas syringae strains were isolated from five onion plants and 18 onion seeds. The symptoms on leaves and seed stalks were irregular lesions with necrotic centres and water soaked margins. The aim of the study was to characterize these P. syringae strains using Biolog GN III carbon source utilization, multilocus sequence typing (MLST) based on partial sequences of four housekeeping genes (cts, gapA, gyrB and rpoD), and to determine whether or not the strains were pathogenic on onion (cv. Granex 33), chive (Allium schoenoprasum cv. Grasiue), leek (Allium porrum cv. Giant Italian) and spring onion (Allium fistulosum cv. Salotte) plants. Both Biolog analysis and MLST analysis separated onion strains into two clusters, one supporting the existence of a new pathovar of P. syringae, and the other corresponding to P. syringae pv. porri. Pseudomonas syringae strains belonging to the new pathovar we pathogenic only on onion plants of the Allium spp. tested. The results of this study revealed that bacterial blight of onion in South Africa is caused by two pathovars of P. syringae sensu lato, namely, the newly described pathovar, allii, and P. syringae pv. porri. The symptoms caused by these two pathovars in the field were indistinguishable.

In December 2006, symptoms typical of iris yellow spot caused by Iris yellow spot virus (IYSV; genus Tospovirus, family Bunyaviridae) were observed on scapes (seed stalks) in an onion (Allium cepa L.) seed crop in the Klein Karoo of the Western Cape Province, South Africa. Symptoms included diamond-shaped chlorotic or necrotic lesions on the scapes, some of which had ‘green-islands’ with nested diamond-shaped lesions, as well as indistinct, circular to irregular, chlorotic or necrotic lesions of various sizes. At the time symptoms were observed, approximately 5% of the scapes had lodged as a result of extensive lesions resembling those caused by IYSV. The crop was 2 to 3 weeks from harvest. Symptomatic tissue from two plants (two samples from one plant and four samples from the other plant) was tested for IYSV by reverse-transcriptase (RT)-PCR. Total RNA was extracted from symptomatic scape tissue with the SV Total RNA Isolation System (Promega, Madison, WI) according to the manufacturer's instructions. First strand cDNA was synthesized with the RevertAid H Minus First Strand cDNA Synthesis kit (Fermentas Inc., Hanover, MD), followed by PCR amplification with primers IYSV-For (TGG YGG AGA TGY RGA TGT GGT) and IYSV-Rev (ATT YTT GGG TTT AGA AGA CTC ACC), which amplify the nucleocapsid (NP) gene of IYSV. An amplicon of expected size (approximately 750 bp) was observed for each of the symptomatic plants assayed and was sequenced. Comparison of the sequence (GenBank Accession No. EF579801) with GenBank sequences revealed 95% sequence identity with the NP gene of IYSV GenBank Accession No. EF419888, with eight amino acid differences. The known geographic distribution of IYSV in onion bulb or seed crops has increased rapidly in recent years in many areas of the world (1). To our knowledge, this is the first confirmation of IYSV in South Africa. Approximately 6,100 ha of onion bulb crops are grown annually in South Africa in the Western Cape, Kwazulu Natal, Limpopo, and Northern Cape provinces, and 600 ha of onion seed crops are grown primarily in the semi-arid regions of the Western Cape. Examination of an additional 10 onion seed crops in the Klein Karoo during January 2007 revealed the presence of iris yellow spot in three more crops at approximately 5% incidence in each crop. The four symptomatic crops had all been planted as bulb-to-seed crops, using vernalized bulbs produced on the same farm. This suggests that IYSV may have been disseminated into the seed crops on the vernalized bulbs, either as infected bulb tissue or in viruliferous thrips on the bulbs. Reference: (1) D. H. Gent et al. Plant Dis. 90:1468, 2006.

In 2007, leaf spots were observed on arugula (Eruca vesicaria subsp. sativa cv. My Way) grown under sprinkler irrigation for fresh market in conventional and organic production fields located above 1,200 m (4,000 feet) in Nevada (NV). Approximately 30% of each planting was affected. Initially, symptoms consisted of small (0.80) to P. syringae. Amplification of DNA between repetitive bacterial sequences (rep-PCR) using the BOXA1R primer resulted in identical banding patterns for the NV arugula strains and P. syringae pv. alisalensis from arugula in California (1). Koch's postulates were completed by confirming pathogenicity of the isolated strains on the arugula cvs. Italian and Astro. Strains were grown on nutrient agar for 48 h at 27°C, adjusted to 108 CFU/ml in sterile 0.01 M phosphate buffer (pH 7.0), and spray inoculated until runoff onto 2- to 3-week-old plants. Control plants were similarly sprayed with sterile phosphate buffer. Plants were held for 2 days in a mist chamber and 7 days on a greenhouse bench (24 to 26°C). Angular lesions similar to symptoms observed on the original plants developed on leaves of all inoculated arugula plants. In addition, some plants developed blackening of the smaller veins accompanied by chlorosis of the surrounding interveinal tissue in 10- to 20-mm diameter areas of the leaves. Small black lesions (as much as 10 mm long) were also observed on the petioles. Bacterial strains reisolated from the symptomatic tissue were identical to P. syringae pv. alisalensis by rep-PCR. Control plants remained symptomless. Similar inoculation and incubation methods confirmed that the host range of the NV arugula isolates was identical to that of known strains of P. syringae pv. alisalensis. The arugula and P. syringae pv. alisalensis isolates caused leaf spots on broccoli raab (Brassica rapa subsp. rapa cv. Sorento) and oats (Avena sativa cv. Montezuma). Pathogenicity tests were repeated. This confirms that the leaf spot observed on conventionally and organically grown arugula in NV was caused by P. syringae pv. alisalensis. To our knowledge, this is the first report of this disease on arugula in NV. References: (1) C. T. Bull et al. Plant Dis. 88:1384, 2004. (2) R. A. Lelliott. J. Appl. Bacteriol. 29:470, 1966.

In August of 2006, onion plants of cv. Redwing exhibiting premature dieback and bulb rot were obtained from a commercial onion crop under center pivot irrigation in the Columbia Basin of Washington State. High temperatures during the summer were similar to those in 2004, which preceded significant outbreaks of Enterobacter rot of onion bulbs in storage. Fungal pathogens of onion were not observed. Bacteria from infected bulb tissue were isolated and purified on nutrient broth yeast extract (NBY) agar, and 537 isolates were evaluated for the ability to ferment glucose anaerobically. Of the facultative anaerobes (~50% of all isolates), 48 isolates were arginine dihydrolase positive, indole negative, and unable to degrade pectin, i.e., characteristics typical of the genus Enterobacter (2), which includes Enterobacter cloacae, a bacterial pathogen reported to cause onion bulb rot in California and Colorado (1,3). Sixteen of the putative Enterobacter isolates, along with four strains of E. cloacae known to be pathogenic on onion (1) (ATCC 23355 and ATCC 13047, 310 (H. F. Schwartz, Colorado State University), and E6 (J. Loper, USDA ARS), were tested for pathogenicity on onion bulbs (8 to 10 cm in diameter; cv. Tamara). The isolates were grown overnight in NBY broth at 28°C, harvested by centrifugation and resuspended to an OD600 = 0.3 (~108 CFU/ml) in sterile distilled water. After the outermost fleshy scale of each bulb was removed, each bulb was surface disinfected in 0.6% NaOCl for 2 min, dipped in sterile distilled water, and then dipped in 95% ethanol. Each bulb was air dried before a 0.5-ml aliquot of bacterial suspension was injected into the shoulder of the bulb with a 20-gauge needle. Three bulbs were inoculated for each isolate, placed in individual plastic bags, sealed, and incubated at 30°C in the dark. Three bulbs injected with water and three noninjected bulbs served as controls. After 14 days, each bulb was sliced through the center and rated for rot. Thirteen isolates induced rot symptoms on the inner fleshy scales of all inoculated bulbs. Of these, seven also caused tan-to-brown discoloration of the inner fleshy scales; similar symptoms were caused by the four pathogenic reference strains of E. cloacae (1). No symptoms were observed in any of the controls. Symptoms were not observed when the bacteria, prepared as described above, were infiltrated into onion leaves. Bacteria were reisolated from the symptomatic inoculated bulb tissue and confirmed to be Enterobacter spp. by the above physiological tests. In addition, an isolate designated ECWSU2 and the corresponding strain recovered from one of the inoculated symptomatic bulbs, along with the four reference strains, were evaluated for anaerobic growth on a variety of carbon sources by using API 50 CHE test strips (bio Mérieux Vitek, Inc., Hazlewood, MO). The physiological test data along with sequence analysis of a portion of the 16S rRNA gene of each isolate confirmed all of these isolates to be E. cloacae (4; Ribosomal Database Project [ http://rdp.cme.msu.edu/ ]). To our knowledge, this is the first report of E. cloacae causing a bulb rot of onion in Washington State. References: (1) A. L. Bishop and R. M. Davis. Plant Dis. 74:692, 1990. (2) J. G. Holt et al. Bergey's Manual of Determinative Bacteriology. Williams and Wilkins, Baltimore, MD, 1994. (3) H. F. Schwartz and K. Otto. Plant Dis. 84:808, 2000. (4) L. Verdonck et al. Int. J. Syst. Bacteriol. 37:4, 1987.

From 1998 through 2002, commercial chives (Allium schoenoprasum) in coastal California (Monterey County) were damaged by an undescribed disease. Initial symptoms were chlorosis and tan-colored necrosis at the leaf tips; as the disease progressed, extensive tan-to-light brown discoloration extended down affected leaves, resulting in their death. The damage prevented growers from harvesting affected crops. Stems of the chive plants were unaffected. Diseased plants continued to grow new leaves that subsequently became infected. A fungus was consistently isolated from symptomatic leaves. Isolates grown on potato dextrose agar (PDA) in petri plates incubated at 24°C under fluorescent lights produced extensive mycelial growth without conidia. However, on onion leaf straw agar (2), the isolates produced abundantly sporulating colonies with conidiophores and conidia typical of a Botrytis species. Conidiophores rarely exceeded 1 mm long. Ellipsoidal conidia measured 11 to 17 × 5 to 8 μm. On green bean pod agar (4), the isolates produced a few, black, irregularly shaped sclerotia measuring 1 to 2 mm in diameter. Morphological comparisons were made on PDA between five chive isolates and isolates of the following Botrytis species known to infect Allium species (1): B. aclada BA5, B. allii BA3, B. byssoidea ATCC 60837, B. cinerea from an onion seed crop, B. porri 749, B. squamosa 392, and B. tulipae GC-1. B. elliptica strain MARLI-3 was also compared with the chive isolates. Chive isolates produced floccose, off white-to-light tan mycelium, lacked sporulation (except where mycelium contacted the edge of the plastic petri dish), and did not form sclerotia on PDA, thereby resembling B. byssoidea. Identification of the chive isolates as B. byssoidea was confirmed by ApoI restriction fragment length polymorphism digests of a 423-bp PCR amplicon obtained from each of the five chive isolates and the eight known Botrytis species (1,3). Pathogenicity of the chive isolates of B. byssoidea was confirmed by spraying a conidial suspension (1 × 105 conidia/ml) of each of 12 isolates onto chive (cv. Fine Leaved) and onion (A. cepa cv. Southport White) plants until runoff, incubating the plants in a humidity chamber at 24 to 26°C for 48 h and then maintaining the plants under ambient light in a greenhouse. After 6 to 8 days, inoculated chives and onions developed symptoms similar to those observed in the field and B. byssoidea was reisolated. Noninoculated control chives and onions sprayed with distilled water did not develop symptoms. The experiment was conducted three times and the results were the same. To our knowledge, this is the first report of a leaf blight of chive caused by B. byssoidea in North America. After 2002, the commercial chive plantings were placed on farms further east in Monterey County away from the coast. The disease has not been observed since this move to a drier climate. References: (1) M. I. Chilvers and L. J. du Toit. Online publication. doi:10.1094/PHP-2006-1127-01-DG. Plant Health Progress, 2006. (2) L. A. Ellerbrock and J. W. Lorbeer. Phytopathology 67:219, 1977. (3) K. Nielsen et al. Plant Dis. 86:682, 2002. (4) A. H. C. van Bruggen and P. A. Arneson. Plant Dis. 69:966, 1985.

Sixty-nine storage onion (Allium cepa) cultivars (seven white, five red, and 57 yellow cultivars) were evaluated in the Washington State University Onion Cultivar Trials in the semiarid Columbia Basin of central Washington in 2007–08 and/or 2008–09. Each cultivar was inoculated with Enterobacter cloacae, cured, stored under commercial storage conditions, and evaluated for bacterial storage rot symptoms approximately 4.5 months after storage. Noninoculated bulbs of each cultivar served as a control treatment in each experiment. In addition, bulbs injected with water served as a second control treatment in the 2008–09 experiment. Inoculation of onion bulbs with E. cloacae resulted in significantly higher incidence and severity of Enterobacter bulb decay compared to noninoculated bulbs and bulbs injected with sterile water. For bulbs inoculated with E. cloacae, mean severity of bacterial storage rot per cultivar ranged from 5 to 19% of the cross-section evaluated for each onion bulb in 2007–08 and from 9 to 29% in 2008–09. For noninoculated bulbs, mean severity ranged from 0 to 1% in 2007–08 and 0 to 3% in 2008–09. For bulbs injected with water in the 2008–09 experiment, severity of bulb rot ranged from 0 to 10% per cultivar, with four cultivars (OLYX05-26, RE-E, Redwing, and Talon) displaying bulb rot ratings significantly greater than 0%. For the 33 cultivars included in both experiments, a significant correlation in bulb rot severity ratings was detected for the 2007–08 versus 2008–09 experiments (r = 0.43 at P = 0.013). Redwing, Red Bull, T-433, Centerstone, and Salsa had low severity ratings in both experiments; whereas Montero, OLYS05N5, Caveat, and Granero had severe bulb rot ratings in both experiments. The results demonstrate that it should be possible to select for increased resistance to Enterobacter bulb decay in storage onion cultivars.

Schroeder, B. K., and du Toit, L. J. 2010. Effects of postharvest onion curing parameters on Enterobacter bulb decay in storage. Plant Dis. 94:1425-1430. Enterobacter bulb decay is a recently described storage disease of onion (Allium cepa) bulbs caused by Enterobacter cloacae. The disease is generally considered minor but, on occasion, can cause significant losses for onion producers. The impact of postharvest curing temperature and duration on Enterobacter bulb decay of onion was evaluated by inoculating bulbs of the cultivars Redwing and Vaquero with E. cloacae after harvest, curing the bulbs at 25, 30, 35, or 40°C for 2 or 14 days, and storing the bulbs at 5°C for 1, 2, or 3 months. Noninoculated bulbs and bulbs injected with sterile water served as control treatments. The trial was completed using bulbs harvested from commercial onion crops grown in the semi-arid Columbia Basin of central Washington in each of 2008–09 (center-pivot irrigated crop) and 2009–10 (drip irrigated crop). Severity of bulb rot was assessed by cutting each bulb down the center from the neck to the basal plate, and rating the percentage of cut surface area with bacterial rot symptoms. Bulb rot severity was negligible for noninoculated bulbs (mean of 0.3% in the 2008–09 storage trial and 1.0% in the 2009–10 storage trial) and bulbs injected with water (0.8% in the 2008–09 trial and 1.3% in the 2009–10 trial) compared to bulbs inoculated with E. cloacae (15.3% in 2008–09 and 23.3% in 2009–10). Severity of Enterobacter bulb decay was affected significantly (P < 0.05) by season (trial), cultivar, curing temperature, curing duration, and storage duration, with significant interactions among these factors. Enterobacter bulb decay was significantly more severe for bulbs cured at 40°C than for bulbs cured at 25, 30, or 35°C. This effect was even greater when bulbs were cured for 14 days versus 2 days prior to cold storage, and in bulbs stored for 2 or 3 months after curing compared to bulbs stored for 1 month. The increase in bulb rot severity caused by curing bulbs at 40°C for 14 days compared to lower temperatures and shorter durations was greater for Vaquero than Redwing, particularly in the 2008–09 trial. The results suggest that curing temperatures ≤35°C should significantly reduce the risk of Enterobacter bulb decay in storage for these cultivars. If higher curing temperatures are used in order to dry onion necks for long-term storage and reduce the risk of fungal diseases such as neck rot (caused by Botrytis spp.), a shorter curing duration may be necessary to minimize the risk of Enterobacter bulb decay in storage.

The influence of postharvest curing temperature and duration on development of slippery skin (caused by Burkholderia gladioli pv. alliicola) and sour skin (caused by B. cepacia) in onion (Allium cepa) bulbs during storage was evaluated by inoculating bulbs of the storage cultivars ‘Redwing’ and ‘Vaquero’ with each of the pathogens after harvest, curing the bulbs at 25, 30, 35, or 40°C for 2 or 14 days, and storing the bulbs at 5°C for 1, 2, or 3 months. Noninoculated bulbs and bulbs injected with sterile water served as control treatments. The onion bulbs were from drip-irrigated, commercial onion crops grown in the semiarid Columbia Basin of central Washington in 2009 and 2010. Each bulb was cut through the point of inoculation from the neck to the basal plate to assess severity of bulb rot (percentage of cut bulb surface area with bacterial rot symptoms) after 1, 2, or 3 months of storage. Bulb rot severity in the 2009–10 and 2010–11 trials was negligible for noninoculated bulbs (mean of 4.0 and 4.5%, respectively) and bulbs injected with water (6.2 and 10.1%, respectively) compared with bulbs inoculated with B. cepacia (34.6 and 39.8%, respectively) and B. gladioli pv. alliicola (20.7 and 27.4%, respectively). Bulbs inoculated with B. cepacia developed significantly more severe rot than those inoculated with B. gladioli pv. alliicola, even though a 10-fold greater inoculum concentration was used for B. gladioli pv. alliicola, demonstrating the more aggressive nature of B. cepacia compared with B. gladioli pv. alliicola. Severity of bulb decay caused by B. cepacia or B. gladioli pv. alliicola was affected significantly (P < 0.05) by season (trial), cultivar, curing temperature, curing duration, and storage duration, with significant interactions among these factors. In both trials and for both pathogens, bulb rot was significantly more severe the greater the curing temperature and the severity of bulb rot was significantly greater when bulbs were cured for 14 versus 2 days prior to cold storage. Overall, the severity of bulb rot was greater with a longer duration of storage after curing. This increase in bulb rot severity, which resulted from an increase in curing temperature and duration, was significantly greater for Vaquero than Redwing and significantly greater for bulbs inoculated with B. cepacia than B. gladioli pv. alliicola. The results suggest that postharvest curing at temperatures

Okubara, P. A., Harrison, L. A., Gatch, E. W., Vandemark, G., Schroeder, K. L., and du Toit, L. J. 2013. Development and evaluation of a TaqMan real-time PCR assay for Fusarium oxysporum f. sp. spinaciae. Plant Dis. 97:927-937. Fusarium oxysporum f. sp. spinaciae, causal agent of spinach Fusarium wilt, is an important soilborne pathogen in many areas of the world where spinach is grown. The pathogen is persistent in acid soils of maritime western Oregon and Washington, the only region of the United States suitable for commercial spinach seed production. A TaqMan real-time polymerase chain reaction (PCR) assay was developed for rapid identification and quantification of the pathogen, based on sequencing the intergenic spacer (IGS) region of rDNA of isolates of the pathogen. A guanine single-nucleotide polymorphism (G SNP) was detected in the IGS sequences of 36 geographically diverse isolates of F. oxysporum f. sp. spinaciae but not in the sequences of 64 isolates representing other formae speciales and 33 isolates representing other fungal species or genera. The SNP was used to develop a probe for a real-time PCR assay. The real-time PCR assay detected F. oxysporum f. sp. spinaciae at 3–14,056 CFU/g of soil in 82 soil samples collected over 3 years from naturally infested spinach seed production sites in western Washington, although a reliable detection limit of the assay was determined to be 11 CFU/g of soil. A significant (P < 0.05), positive correlation between enumeration of F. oxysporum on Komada’s agar and quantification of the pathogen using the TaqMan assay was observed in a comparison of 82 soil samples. Correlations between pathogen DNA levels, Fusarium wilt severity ratings, and spinach biomass were significantly positive for one set of naturally infested soils but not between pathogen DNA levels, wilt incidence ratings, and spinach biomass for other soil samples, suggesting that soilborne pathogen population is not the sole determinant of spinach Fusarium wilt incidence or severity. The presence of the G SNP detected in one isolate of each of F. oxysporum ff. spp. lageneriae, lilii, melongenae, and raphani and reaction of the real-time PCR assay with 16 of 22 nonpathogenic isolates of F. oxysporum associated with spinach plants or soil in which spinach had been grown potentially limits the application of this assay. Nonetheless, because all isolates of F. oxysporum f. sp. spinaciae tested positive with the real-time PCR assay, the assay may provide a valuable means of screening for resistance to Fusarium wilt by quantifying development of the pathogen in spinach plants inoculated with the pathogen.

In 2012 and 2013, foliar symptoms were observed in certified organic, 2- to 4-ha crops of Echinacea angustifolia and E. purpurea in Grant and Klickitat counties, WA. White pustules were predominant on the abaxial leaf surface, increased in number, and coalesced on E. angustifolia, with 100% infection by the end of the season; in contrast, symptoms remained sparse on E. purpurea. Symptomatic leaves of each species were collected in May 2013 in Grant Co. Sori and sporangia were typical of those of white rust on Asteraceae caused by Pustula obtusata (1), originally named Albugo tragopogonis, then P. tragopogonis (4). Hyaline sporangia (n = 50) averaged 21 ± 2 × 20 ± 2 μm (16 to 25 × 16 to 24 μm) with a 2.6 ± 0.8 μm (1.0 to 4.0 μm) thick wall. Honey-colored to dark brown oospores were embedded in the abaxial leaf surface surrounding sori on older leaves. Oospores (n = 50) averaged 75 ± 7 × 63 ± 6 μm (60 to 96 × 52 to 76 μm) and 52 ± 4 × 51 ± 4 μm (44 to 65 × 44 to 60 μm) with (including protruberances) and without the hyaline outer wall, respectively. Sori were excised and shaken in 100 ml cold (4°C), deionized water at 400 rpm for 15 min on a gyrotory shaker. DNA extracted from the resulting spore suspension was subjected to a PCR assay using oomycete specific primers (2) to amplify the cytochrome oxidase subunit II (cox2) region of mtDNA (3). The 511-nt consensus sequence of the PCR product (GenBank Accession No. KF981439) was 98% identical to a cox2 sequence of A. tragopogonis from sunflower (Helianthus annuus) (AY286221.1), and 96% identical to cox2 sequences of P. tragopogonis (GU292167.1 and GU292168.1) (= P. obtusata) (1,2,4). Pathogenicity of the white rust isolate was confirmed by inoculating 49-day-old plants of E. angustifolia and E. purpurea with a spore suspension prepared as described above. One plant/species was placed in each of six clear plastic bags in a growth chamber at 18°C with a 12-h day/12-h night cycle for 48 h. Five replicate sets of one plant/species were each inoculated with 2.2 × 105 spores/ml on the adaxial and abaxial leaf surfaces using an airbrush (8 psi). One plant/species was sprayed with water as a control treatment. The plants were resealed in the bags for 48 h. After 7 days, white pustules were observed on at least one plant species. The plants were placed in plastic bags again overnight, and re-inoculated with 2.9 × 105 spores/ml. In addition, two sunflower plants at the 4-true-leaf stage were incubated in each of two plastic bags overnight, and inoculated with the spore suspension. Two additional sunflower plants were treated with water as control plants. All plants were removed from the bags after 48 h. White rust sori with sporangia developed on all inoculated Echinacea plants within 10 days, but not on control plants of either species, nor inoculated and non-inoculated sunflower plants, verifying that the pathogen was not P. helianthicola (1,2). Since the cox2 sequence was closest to that of a sunflower white rust isolate, the pathogen appears to be closer to P. helianthicola than P. obtusata, and may be a new Pustula species. To our knowledge, this is the first documentation of white rust on E. angustifolia and E. purpurea in North America. The severity of white rust on E. angustifolia highlights the need for effective management practices. References: (1) C. Rost and M. Thines. Mycol. Progress 11:351, 2012. (2) O. Spring et al. Eur. J. Plant Pathol 131:519, 2011. (3) S. Telle and M. Thines. PloS ONE 3(10):e3584, 2008. (4) M. Thines and O. Spring. Mycotaxon 92:443, 2005.

We present the confusion-limited 1.28 GHz MeerKAT DEEP2 image covering one $\approx 68'$ FWHM primary beam area with $7.6''$ FWHM resolution and $0.55 \pm 0.01$ $\mu$Jy/beam rms noise. Its J2000 center position $\alpha=04^h 13^m 26.4^s$, $\delta=-80^\circ 00' 00''$ was selected to minimize artifacts caused by bright sources. We introduce the new 64-element MeerKAT array and describe commissioning observations to measure the primary beam attenuation pattern, estimate telescope pointing errors, and pinpoint $(u,v)$ coordinate errors caused by offsets in frequency or time. We constructed a 1.4 GHz differential source count by combining a power-law count fit to the DEEP2 confusion $P(D)$ distribution from $0.25$ to $10$ $\mu$Jy with counts of individual DEEP2 sources between $10$ $\mu$Jy and $2.5$ mJy. Most sources fainter than $S \sim 100$ $\mu$Jy are distant star-forming galaxies obeying the FIR/radio correlation, and sources stronger than $0.25$ $\mu$Jy account for $\sim93\%$ of the radio background produced by star-forming galaxies. For the first time, the DEEP2 source count has reached the depth needed to reveal the majority of the star formation history of the universe. A pure luminosity evolution of the 1.4 GHz local luminosity function consistent with the Madau & Dickinson (2014) model for the evolution of star-forming galaxies based on UV and infrared data underpredicts our 1.4 GHz source count in the range $-5 \lesssim \log[S(\mathrm{Jy})] \lesssim -4$., Comment: 20 pages, 18 figures. Accepted for publication in ApJ

In November 2017, leaf spots were observed in a fresh market spinach crop of cultivar SV2157VB in New Jersey at ∼20% incidence but not in the adjacent crop of Unipack-151. Pale tan lesions (3 to 8 mm in diameter) had gray sporulation at the centers. Symptomatic leaf pieces were surface-sterilized in 0.6% NaOCl for 60 s, triple-rinsed in sterilized water, dried, and plated onto PDA and water agar (each with 100 µg of chloramphenicol/ml). Seven isolates all produced hyaline, straight to slightly curved conidia, mostly two- to three-septate, 20.0 to 82.0 µm (45.2 ± 11.3 µm, mean ± standard deviation) × 6.0 to 11.0 µm (8.1 ± 1.0 µm) (n = 312), with no significant differences among isolates. Spore characteristics matched those of Cercospora spp. (Świderska-Burek 2015). The consensus sequence of the calmodulin gene (cmdA) amplified from all seven isolates using primers CALDF1 and CALDR (Lawrence et al. 2013) (GenBank accession no. MN422444) was 99.78% identical to that of Cercospora cf. chenopodii (JX142839.1), which is not differentiated from C. chenopodii by this gene (Groenewald et al. 2013). Actin (actA) primers ACT-512F and ACT-783R generated an identical sequence for the isolates (MN422442) that was 99.55% identical to that of C. chenopodii (JX143081.1) (Carbone and Kohn 1999). The translation elongation factor 1-α (TEF1-α) sequence of the isolates (MN422445) had 99.45% identity to the sequence of a voucher specimen of C. chenopodii (JX143327.1). C. beticola-specific primers CbCALF and CbCALR did not amplify DNA of these isolates, only DNA of control isolates of C. beticola (Knight et al. 2019). Based on a phylogenetic tree inferred from concatenated actA, cmdA, ITS rDNA, and TEF1-α sequences, the isolates clustered with the voucher strain C. chenopodii CBS 132620. Six isolates were each tested for pathogenicity on four 33-day-old plants of each of spinach cultivars Mandolin, SV2157VB, Unipack-151, and Viroflay; sugar beet cultivar KDH4-9 (USDA National Plant Germplasm System PI 683513, homozygous susceptible to C. beticola), red beet cultivars Red Ace and Ruby Queen, and Swiss chard cultivar Silverado. Plants were enclosed in plastic bags for 24 h, atomized with a spore suspension (1 × 10⁴ conidia/ml) prepared from clarified V8 agar plates of each isolate, and returned to the bags for 24 h. Four non-inoculated control plants of each cultivar were atomized with water as control treatments. Beet and chard plants were placed in a greenhouse and spinach plants in a growth chamber with 10 h lighting/day to avoid bolting under 16-h summer days in Washington. Symptoms had not developed after 7 days, at which time spinach plants were moved to the greenhouse. By 9 days, leaf spots resembling those on the original leaves were observed on Mandolin and SV2157VB. By 14 days, there were leaf spots on all four spinach cultivars. Symptoms were most severe on SV2157VB (18.3 ± 2.0% mean ± standard error of leaf area), followed by Mandolin and Viroflay (8.8 ± 1.6%), and then Unipack-151 (2 ± 0.5%). Symptoms did not develop on non-inoculated spinach or inoculated and non-inoculated sugar beet, table beet, and Swiss chard. Cercospora could only be reisolated from symptomatic spinach plants, with the isolates confirmed as C. chenopodii based on actA sequences. Although C. beticola has been reported to cause Cercospora leaf spot of spinach (Knight et al. 2018), this is the first report of C. chenopodii causing a leaf spot of spinach in the United States. Research is needed to evaluate impacts of this species on additional spinach cultivars and management options.

New radio (MeerKAT and Parkes) and X-ray (XMM-Newton, Swift, Chandra, and NuSTAR) observations of PSR J1622-4950 indicate that the magnetar, in a quiescent state since at least early 2015, reactivated between 2017 March 19 and April 5. The radio flux density, while variable, is approximately 100x larger than during its dormant state. The X-ray flux one month after reactivation was at least 800x larger than during quiescence, and has been decaying exponentially on a 111+/-19 day timescale. This high-flux state, together with a radio-derived rotational ephemeris, enabled for the first time the detection of X-ray pulsations for this magnetar. At 5%, the 0.3-6 keV pulsed fraction is comparable to the smallest observed for magnetars. The overall pulsar geometry inferred from polarized radio emission appears to be broadly consistent with that determined 6-8 years earlier. However, rotating vector model fits suggest that we are now seeing radio emission from a different location in the magnetosphere than previously. This indicates a novel way in which radio emission from magnetars can differ from that of ordinary pulsars. The torque on the neutron star is varying rapidly and unsteadily, as is common for magnetars following outburst, having changed by a factor of 7 within six months of reactivation., Comment: Published in ApJ (2018 April 5); 13 pages, 4 figures

Aims To develop multiplex TaqMan real-time PCR assays for detection of spinach seedborne pathogens that cause economically important diseases on spinach. Methods and Results Primers and probes were designed from conserved sequences of the internal transcribed spacer (for Peronospora farinosa f. sp. spinaciae and Stemphylium botryosum), the intergenic spacer (for Verticillium dahliae) and the elongation factor 1 alpha (for Cladosporium variabile) regions of DNA. The TaqMan assays were tested on DNA extracted from numerous isolates of the four target pathogens, as well as a wide range of nontarget, related fungi or oomycetes and numerous saprophytes commonly found on spinach seed. Multiplex real-time PCR assays were evaluated by detecting two or three target pathogens simultaneously. Singular and multiplex real-time PCR assays were also applied to DNA extracted from bulked seed and single spinach seed. Conclusions The real-time PCR assays were species-specific and sensitive. Singular or multiplex real-time PCR assays could detect target pathogens from both bulked seed samples as well as single spinach seed. Significance and Impact of the Study The freeze-blotter assay that is currently routinely used in the spinach seed industry to detect and quantify three fungal seedborne pathogens of spinach (C. variabile, S. botryosum and V. dahliae) is quite laborious and takes several weeks to process. The real-time PCR assays developed in this study are more sensitive and can be completed in a single day. As the assays can be applied easily for routine seed inspections, these tools could be very useful to the spinach seed industry.

During 2009 and 2010, 45 isolates of Rhizoctonia spp. were recovered from onion bulb crops in the semiarid Columbia Basin of Oregon and Washington, in which patches of severely stunted onion plants developed following rotation with winter cereal cover crops. Characterization of isolates recovered from naturally infested soil and roots was performed by sequence analysis of the ribosomal DNA (rDNA) internal transcribed spacer region, with the majority of isolates (64%) identified as Rhizoctonia solani. In steam-pasteurized field soil, stunting of onion was caused by isolates of R. solani anastamosis groups (AGs) 2-1, 3, 4, and 8, as well as Waitea circinata var. circinata and binucleate Rhizoctonia AG E evaluated at 13 and 8 or 15 and 15°C day and night temperatures, respectively, typical of spring planting conditions in the Columbia Basin. Isolates of R. solani AG 5 as well as binucleate AG A and I were nonpathogenic. The most virulent isolates belonged to AG 8, although an AG 3 and an AG E isolate were also highly virulent. Isolates of AG 2-1 and 3 caused moderate levels of disease, while isolates of AG 4 and W. circinata var. circinata caused low levels of disease. Emergence was reduced by isolates of AG 2-1, 3, and E. When the various AGs were grown at temperatures of 5 to 30°C, the relative growth rate of the Rhizoctonia isolates was not positively correlated with virulence on onion within an AG.

Phomopsis black root rot of cucumber (Cucumis sativus L.), caused by Diaporthe sclerotioides (syn. Phomopsis sclerotioides), has been reported in Austria, Britain, Canada, Denmark, France, Germany, Italy, Japan, Malaysia, the Netherlands, and Norway (Shishido et al. 2016). In August 2017, wilted plants were observed in patches comprising 10% of a 5-ha organic cucumber crop in Skagit Co., WA, after fruit had formed. Crowns, tap roots, and secondary roots had pink to brown, dry, corky lesions, black pseudostromata, and rectangular pseudosclerotia within cortical cells. Sections of symptomatic roots and crowns (≤10 mm long) of eight plants selected randomly were surface-sterilized in 0.6% NaOCl for 3 to 5 min, triple-rinsed in sterilized water, dried on sterilized blotters, plated on water agar, and incubated at 24 ± 2°C with a natural day/night cycle. Hyphae were transferred to 1/2-strength PDA amended with chloramphenicol (100 ppm). After 2 weeks, each isolate covered the plate with gray-brown, dense mycelium. Flat, brown-black, irregular pseudostromata formed in the medium. Five isolates were grown in 1/2-strength potato dextrose broth on a shaker for 7 days, mycelia harvested, DNA extracted, and the internal transcribed spacer (ITS) 1-5.8S-ITS2 region of ribosomal DNA amplified using universal eukaryotic primers UN-UP18S42 and UN-LO28S576B (Schroeder et al. 2006). The sequences of isolates Dsl004, Dsl005, Dsl006, and Dsl008 (GenBank accession nos. MG434673.1, MG434674.1, MG434675.1, and MG434676.1, respectively) had 100% identity to that of a D. sclerotioides isolate (NR_111069.1); the sequence of Dsl002 (MG434672.1) had 99% identity because of a 7-nt insertion in the ITS1 region. All five isolates and DNA of D. sclerotioides ATCC18585 (ex-type culture) produced the expected 392-bp band of amplified DNA from the ITS rDNA using the highly specific primers CPs-1 and CPs-2 (Shishido et al. 2010). In addition, a 566-nt consensus sequence of the TEF 1-α gene of Dsl002, Dsl004 to Dsl006, and Dsl008 (MG868937) generated by PCR assay with primers EF-2F and EF-5AR (Taskin et al. 2010) was 100% identical to that of D. sclerotioides ATCC18585 (MG868936). Pathogenicity of the five isolates on cucumber was verified in a greenhouse using two methods, direct-seeding and transplanting. Two-week-old colonized PDA plates of each isolate were cut into 3 mm³ pieces and mixed in Sunshine Potting Mix #1 (Sungro Horticulture, Canada) (half a plate/1.0 liter potting mix/15-cm-diameter pot). A nontreated seed (cv. Turbo) was then planted in the medium in each of five replicate pots/isolate, and a 10-day-old Turbo seedling was transplanted into each of five replicate pots/isolate. For the control treatment, potting medium was amended with noncolonized PDA (five direct-seeded and five transplanted replicates). Plants were maintained at 18 to 26°C with 10 h light/day. Dsl004, Dsl005, Dsl006, and Dsl008 caused wilting and death of plants in 3 weeks with the direct-seeding method, and in 4 to 5 weeks for the transplanting method. Dsl002 caused stunting and minor wilting. Control plants remained healthy. The roots of inoculated plants had corky lesions with pseudostromata and pseudosclerotia. D. sclerotioides was reisolated from roots of inoculated plants but not control plants. The species was confirmed morphologically and by ITS rDNA and TEF 1-α sequencing. This is the first report of Phomopsis black root rot of cucumber caused by D. sclerotioides in Washington State or anywhere in the U.S.A. The disease was reported in greenhouse cucumber in neighboring British Columbia, Canada, in 1972 (Ormrod and Christie 1972). Research is needed to assess prevalence of the pathogen and management strategies to limit spread of the disease.

Eastwell, K. C., du Toit, L. J., and Druffel, K. L. 2009. Helleborus net necrosis virus: A new Carlavirus associated with ‘black death’ of Helleborus spp. Plant Dis. 93:332-338. Symptoms of ‘black death’ were observed on Helleborus spp. in each of three independent nurseries from across the United States. A new virus of the genus Carlavirus was identified in association with this disease. Symptomatic plants contained curved, rod-shaped particles averaging 800 by 17 nm, and yielded predominant bands of double-stranded (ds)RNA corresponding to approximately 9.0, 2.6, and 1.7 kbp. Amplification with degenerate primers for carlaviruses yielded a product of approximately 3,000 bp from diseased plants. Complete genomic sequences of two virus isolates were determined. Particle size, dsRNA patterns, genome organization, and sequence were consistent with members of the family Flexiviridae, genus Carlavirus. The name Helleborus net necrosis virus (HeNNV) is proposed for the virus associated with black death of Helleborus spp. in the United States. The sequence of the 3′ terminus of Helleborus mosaic virus (HeMV) (genus Carlavirus) was also determined. Nucleotide sequences of HeNNV and HeMV were only 49% identical, revealing the distinct nature of these viruses. Assays for other viruses failed to reveal a consistent association of any other virus with black death symptoms. Cucumber mosaic virus was detected in hellebore specimens both with and without distinct black death symptoms.

The construction of the seven-dish Karoo Array Telescope (KAT-7) array in the Karoo region of the Northern Cape in South Africa was intended primarily as an engineering prototype for technologies and techniques applicable to the MeerKAT telescope. This paper looks at the main engineering and scientific highlights from this effort, and discusses their applicability to both MeerKAT and other next-generation radio telescopes. In particular, we found that the composite dish surface works well, but it becomes complicated to fabricate for a dish lacking circular symmetry; the Stirling cycle cryogenic system with ion pump to achieve vacuum works but demands much higher maintenance than an equivalent Gifford-McMahon cycle system; the ROACH (Reconfigurable Open Architecture Computing Hardware)-based correlator with SPEAD (Streaming Protocol for Exchanging Astronomical Data) protocol data transfer works very well and KATCP (Karoo Array Telescope Control Protocol) control protocol has proven very flexible and convenient. KAT-7 has also been used for scientific observations where it has a niche in mapping low surface-brightness continuum sources, some extended H I haloes and OH masers in star-forming regions. It can also be used to monitor continuum source variability, observe pulsars, and make Very Long Baseline Interferometry observations.

Pataky, J. K., Raid, R. N., du Toit, L. J., and Schueneman, T. J. 1998. Disease severity and yield of sweet corn hybrids with resistance to northern leaf blight. Plant Dis. 82:57-63. Reactions of supersweet (sh2) sweet corn to northern leaf blight (NLB) and associated yields were evaluated in Belle Glade, Florida and Urbana, Illinois in yield-loss trials, hybrid evaluations, and evaluations of breeding materials. Hybrids differed significantly for NLB in all trials. Severity of NLB ranged from 0 to 66% on 35 sh2 hybrids in yield-loss trials, and from 0 to 60% on 80 sh2 hybrids in hybrid evaluations. NLB ratings ranged from 1 to 9 (approximately 0 to 80% severity) on 375 hybrids and 186 inbred lines in evaluations of breeding materials. Various methods of rating NLB and ratings from multiple dates were highly correlated, with correlation coefficients ranging from 0.76 to 0.98. Yield, measured as weight of ears and number of marketable ears from inoculated plots as a percentage of that from control plots, decreased as disease severity increased. Linear or quadratic regression models explained 31 to 70% of the variation in percent yield as a function of disease severity at harvest. The effects of NLB on yield were limited by NLB-resistance in several hybrids, including CCO 3268, Chieftain, Crisp N Sweet 710A, Day Star, Envy, Forever, GSS 1526, Jupiter, Midship, Prime Plus, Sch 5005, and SummerSweet 7630. Although high levels of partial resistance to NLB were prevalent among 375 new experimental sh2 hybrids and 186 sh2 inbred lines evaluated in 1995, use of the gene HtN may increase in the near future as breeders are incorporating this resistance into new inbreds and hybrids. Breeders and plant pathologists would be wise to continue improving partial resistance to NLB without using the gene HtN in genotypes with adequate levels of partial resistance, because the widespread use of the gene HtN will select for virulent races of Exserohilum turcicum which occur in Florida, or for races with new combinations of virulence.

Severity of bacterial leaf blight (BLB, caused by Acidovorax avenae subsp. avenae) on shrunken-2 (sh2) sweet corn hybrids grown in BLB-conducive environments and sporadic outbreaks of BLB in recent years warranted evaluations of the potential for this disease to cause economic losses. BLB symptoms on 122 sh2 hybrids, 30 sh2 inbred lines, and 29 crosses of the inbreds and the effects of BLB on yield (ear weight and marketable ears) were evaluated in 1994 and 1996. BLB severity ratings for 122 hybrids averaged 3.3 and 3.7 (on a scale of 1 to 9) in 1994 and 1996, respectively. Hybrid means ranged from 1.8 to 5.5 in 1994 and from 1.9 to 5.7 in 1996, with Bayesian LSD values of 1.20 and 1.22, respectively. There were no differences in BLB ratings among hybrids with yellow, white, or bicolored kernels. Severity of symptoms on 30 sh2 inbreds ranged from 1.5 to 5.7, whereas the reactions of 29 crosses of the inbreds ranged from 1.9 to 5. The slope coefficient of the regression of crosses on mid-parent values was not different from 1. Thus, mid-parent values gave a good indication of severity of BLB symptoms on crosses, with the exception of a few crosses that tended to be more severely infected than expected based on mid-parent values. Ear weights and number of marketable ears differed among hybrids in the 1994 trial, but there was no significant effect of BLB treatments on either of these measures of yield. In 1996, ear weights in inoculated plots were 10 and 15% lower than those from noninoculated plots for 2 of 12 hybrids. Despite moderately severe foliar symptoms, BLB did not affect yield substantially in these trials even among hybrids with the most susceptible reactions.

The electric screen Jauman absorber is a stratified cascade of dielectric spacers, interlaced with resistive sheets, which is effective in reducing specular reflection from flat or moderately curved conducting surfaces. Usually, the dielectric constant of the identical spacers is assumed known a priori, and the design problem is to find the sheet surface resistivities that will yield an absorption behavior which meets certain design criteria. This paper presents detail on three efficient and dedicated synthesis algorithms that synthesize absorbers with Butterworth, equiripple, and Chebyshev absorption properties. To the authors' knowledge, the Chebyshev solutions solve the fundamental problem for the first time.

In 2011, bacterial blight of arugula (Eruca vesicaria subsp. sativa; cv. Roquette) was observed in organically grown plants under overhead irrigation in a field near Delano, MN. Approximately 80 to 100% of each planting was affected, with greater rates of infection occurring after periods of high humidity. Small, water-soaked, angular spots apparent on both sides of the leaves comprised the initial symptoms, which sometimes expanded and coalesced. Lesions maintained a dark water-soaked appearance or dried and turned a brown/tan color. Additionally, some lesions were outlined by a purple margin. Blue-green fluorescent pseudomonads were isolated consistently on King's Medium B agar (KMB) from symptomatic leaf tissue surface-disinfested with sodium hypochlorite (0.525%). The isolates nucleated ice and produced levan. Isolates were oxidase and arginine dihydrolase negative. They did not rot potato slices but did induce a hypersensitive reaction in tobacco (Nicotiana tabacum cv. Samsun). These data indicated that the bacteria belonged to Lelliott's LOPAT group 1 (2). DNA fragment banding patterns generated by amplifying DNA of the arugula isolates using repetitive extragenic palindromic sequence–polymerase chain reaction (rep-PCR) and the BOX A1R primer were identical and nearly identical to the banding patterns of the Pseudomonas cannabina pv. alisalensis (formerly P. syringae pv. alisalensis) (1) strain (CFBP1637) and the pathotype strain (CFBP 6866PT), respectively. Pathogenicity was confirmed on the arugula cv. My Way in two independent experiments, each with three replicate plants per treatment. Four isolates were grown on KMB for 48 h at 27°C, suspended in 0.01M potassium phosphate buffer (pH 7.0), and adjusted to 0.6 optical density at 600 nm (approximately 1 × 108 CFU/ml). Five- to six-week old plants were spray-inoculated until run-off, incubated in a humidity chamber for 48 h, and then placed in a greenhouse at 20 to 25°C for symptom development. For negative and positive control treatments, a similar number of plants each were sprayed with sterile buffer or P. cannabina pv. alisalensis strains CFBP1637 and CFBP 6866PT, respectively. Water-soaked and brown/tan lesions similar to the original symptoms appeared on plants inoculated with the arugula isolates and P. cannabina pv. alisalensis strains 7 to 14 days postinoculation. No symptoms developed on plants treated with sterile buffer. The bacterial strains re-isolated from surface-disinfested symptomatic tissue were identical by rep-PCR to the isolates used to inoculate the plants, thus, confirming Koch's postulates. Identical replicated experiments conducted on broccoli raab indicated that the arugula isolates were also pathogens of broccoli raab (Brassica rapa subsp. rapa, the original host from which P. cannabina pv. alisalensis was isolated). To our knowledge, this is the first report of bacterial blight of crucifers caused by P. cannabina pv. alisalensis in Minnesota. Arugula germplasm is being evaluated for resistance to this pathogen as an acceptable management method for organic cropping systems. References: (1) C. T. Bull et al. Syst. Appl. Microbiol. 33:105, 2010. (2) R. A. Lelliott. J. Appl. Bacteriol. 29:470, 1966.

Iris yellow spot virus (IYSV), a tentative virus species in the genus Tospovirus and family Bunyaviridae, is considered a rapidly emerging threat to onion production in the western United States (US). The present study was undertaken to determine the sequence diversity of IYSV isolates from infected onion plants grown in California, Colorado, Idaho, Oregon, Utah and Washington. Using primers derived from the small RNA of IYSV, the complete sequence of the nucleoprotein (NP) gene of each isolate was determined and the sequences compared. In addition, a shallot isolate of IYSV from Washington was included in the study. The US isolates of IYSV shared a high degree of sequence identity (95 to 99%) with one another and to previously reported isolates. Phylogenetic analyses showed that with the exception of one isolate from central Oregon and one isolate from California, all the onion and shallot isolates from the western US clustered together. This cluster also included onion and lisianthus isolates from Japan. A second distinct cluster consisted of isolates from Australia (onion), Brazil (onion), Israel (lisianthus), Japan (alstroemeria), the Netherlands (iris) and Slovenia (leek). The IYSV isolates evaluated in this study appear to represent two distinct groups, one of which largely represents isolates from the western US. Understanding of the population structure of IYSV would potentially provide insights into the molecular epidemiology of this virus.

In August 2004, examination of powdery mildew-infected ‘Russet Burbank’ potato leaves from a furrow-irrigated field in Grant Co., WA, revealed two powdery mildew fungi, one referable to Erysiphe orontii and the other to Leveillula taurica (Lév.) G. Arnaud. Discovery of the two species sporulating together on diseased leaves is consistent with an observation made in the Middle East. This report documents, for the first time, L. taurica on potato in N. America and provides information on distinguishing it from E. orontii. Accepted for publication 9 December 2004. Published 14 December 2004.

A powdery mildew disease of onion has been observed infrequently in the Columbia Basin of Washington State since 1996, but this is the first published report of this disease in the Pacific Northwest. The causal agent was determined to be Leveillula taurica (Lév.) G. Arnaud. Accepted for publication 29 October 2004. Published 29 November 2004.

Results of an investigation into the design of Jaumann absorbers are reported. Jaumann absorbers are effective in minimizing plane wave reflection from a conducting metal surface and exhibit reasonably wide frequency and incidence angle bandwidths. The spacers between the resistive sheets are usually assumed to be lossless and a quarter-wavelength long at the center frequency. It is shown that the numerical minimization technique can result in a design which improves upon the purely analytical methods. Some representative results are shown. >

The authors present lumped-element equivalent circuits for two specific square patches on an electrically thick (0.05 lambda /sub 0/) substrate. The equivalent circuits were derived from experimental data and could be useful in the verification of theoretical techniques. For the particular geometry studied the probe fed patch requires sidelengths approximately 6% shorter than the microstrip fed patch, for the same resonant frequency. The microstrip-fed patch has a sharper resonance and approximately half the bandwidth of the probe-fed patch. Presumably the probe introduces more losses than the microstrip, thus damping the patch resonance. >

A specific linear array of square patches is considered. The array, measured feed radiation, and sources of feed radiation are examined. It is shown that radiation from a coplanar microstrip feed network can degrade the patterns of a linear patch array to an extent that is unacceptable in many applications. The problem arises when the microstrip substrate parameters are chosen to maximize radiation at the patch edges, thus undermining the ability of the feed network to guide waves. One solution is to use a relatively thin, high-relative permittivity substrate. This has the disadvantage of reduced bandwidth. Another approach is to sacrifice the low-cost coplanar feed by placing the feed on the opposite side of the ground plane from the radiating elements, and using coaxial pins to drive the patches. In this way, the radiation and guided wave functions are separated and the substrate parameters can be separately optimized for each. The feed can also be screened. >

Radish (Raphanus sativus L.) seed crops in Washington may annually produce up to 70% of the US and up to 40% of the world supply of radish seed (11). In May and June 2002, severe symptoms of wilting and dieback were observed in a radish stock seed crop in the Columbia Basin of central Washington. Examination of the roots revealed a dark vascular discoloration and root rot, as well as cabbage maggot (Delia radicum L.) larvae with associated feeding injury. Isolations from the symptomatic root tissue onto acidified potato dextrose agar (PDA) revealed the presence of Fusarium oxysporum, identified according to Nelson et al. (8) on the basis of colony morphology and the presence of chlamydospores, microconidia produced in false heads on short monophialides, and abundant macroconidia. The pathogenicity of two of the isolates of F. oxysporum was evaluated in the greenhouse using 2-week-old seedlings of the radish cultivar Champion. For each isolate, 6 seedlings were wounded by tearing the sides and lower end of each transplant plug. The roots were inoculated by soaking the plug in a suspension of approximately 10 5 spores/ml for 60 s, and individually

Tuning the center dipole in a small array, such that it will ultimately exhibit a good active input impedance when used in a large array, is discussed. The presentation addresses theory, timing techniques, measured results, and comments on general applicability.

In summer 2012, bacterial blight symptoms (2) were observed on leaves of carrot plants in 7 out of 70 plots of carrot breeding lines at the Purdue University Meig Horticulture Research Farm, Lafayette, IN. Symptoms included small to large, variably shaped, water-soaked to dry, necrotic lesions, with or without chlorosis, at 2) were surface-sterilized in 1.2% NaOCl for 60 s, triple-rinsed in sterilized, deionized water, dried on sterilized blotter paper, macerated in sterilized water, and a loopful of the suspension was streaked onto yeast dextrose carbonate (YDC) agar medium (1). Colonies with morphology similar to that of strain Car001 of Xanthomonas hortorum pv. carotae from California (3) were obtained consistently from all seven plots, and serial dilutions streaked onto YDC agar medium to obtain pure cultures. One bacterial strain/plot was then subjected to a PCR assay for X. hortorum pv. carotae using the protocol of Meng et al. in (5), except for an annealing temperature of 60°C. All seven Indiana strains and Car001 produced a 355-bp DNA fragment indicative of X. hortorum pv. carotae. The Indiana strains and Car001 were each tested for pathogenicity on five 11-week-old carrot plants of a proprietary Nantes inbred line grown from a seed lot that tested negative for X. hortorum pv. carotae (1,3). Each strain was grown for 16 h in 523 broth (4) on a shaker (200 rpm) at 28°C, and diluted in 0.0125M phosphate buffer to 108 CFU/ml. Approximately 24 h prior to inoculation, the five plants for each strain were enclosed in a large plastic bag to create a moist chamber. The plants were inoculated by atomizing 30 ml of the appropriate bacterial suspension onto the foliage using an airbrush. Five plants inoculated with sterilized phosphate buffer served as a negative control treatment. The plants were re-sealed in plastic bags for 72 h, and placed in a randomized complete block design in a greenhouse set at 25 to 28°C. Symptoms of bacterial blight were first observed 14 days after inoculation, and developed on all inoculated plants by 21 to 28 days after inoculation, with slight variation in severity of symptoms among strains. Symptoms did not develop on negative control plants. Re-isolations were done 32 days after inoculation from symptomatic leaves of three replicate plants/strain and from three plants of the negative control treatment, using the protocol described for the original samples. Bacterial colonies typical of X. hortorum pv. carotae were obtained from symptomatic leaves for all seven Indiana strains and the control strain, but not from the negative control plants. Identity of the re-isolated strains as X. hortorum pv. carotae was confirmed by PCR assay. To our knowledge, this is the first report of bacterial blight of carrot in Indiana. References: (1) M. Asma. Detection of Xanthomonas hortorum pv. carotae on Daucus carota. 7-020. International Rules for Seed Testing, Annex to Chapter 7: Seed Health Testing Methods. Internat. Seed Testing Assoc., Bassersdorf, Switzerland, 2006. (2) R. M. Davis and R. N. Raid. Compendium of Umbelliferous Crop Diseases. The American Phytopathological Society, St. Paul, MN, 2002. (3) L. J. du Toit et al. Plant Dis. 89:896, 2005. (4) E. I. Kado and M. G. Heskett. Phytopathology 60:969, 1970. (5) X. Q. Meng et al. Plant Dis. 88:1226, 2004.

In October 2012, symptoms of cavity spot (1) were observed on roots of two 50 ha, Red Core Chantenay processing carrot (Daucus carota L. subsp. sativus (Hoffm.)) crops in the Columbia Basin of central Washington. Symptoms consisted of sunken, elliptical lesions (3 to 15 mm long) on the root surface. Approximately 6% of the roots in each crop were affected, which was sufficient to present sorting problems for the processor. Symptomatic roots were washed thoroughly in tap water, and then small sections of tissue from the lesion margins were removed aseptically and plated onto water agar (WA) without surface-sterilization. Isolates with morphological characteristics typical of Pythium sulcatum Pratt & Mitchell (2) were obtained consistently from the symptomatic tissue. The genus and species identity of seven isolates was confirmed by sequence analysis of the internal transcribed spacer (ITS) 1-5.8S-ITS2 region of ribosomal DNA (rDNA) using universal eukaryotic primers UN-UP18S42 and UN-LO28S576B with the PCR protocol described by Schroeder et al. (3). The ITS consensus sequences of the seven isolates (Accession Nos. KF509939 to KF509945) were 98 to 99% homologous to ITS sequences of P. sulcatum in GenBank. Pathogenicity of all seven isolates was confirmed by inoculating mature carrot roots of cv. Bolero. Each root was washed with tap water, sprayed to runoff with 70% isopropanol, and dried in a laminar flow hood on sterilized paper toweling. The roots were then placed in plastic bins lined with paper toweling moistened with sterilized, deionized water. Each root was inoculated by placing two 5 mm-diameter agar plugs, taken from the edge of an actively growing WA culture of the appropriate isolate, on the root surface approximately 3 cm apart. Non-colonized agar plugs were used for a non-inoculated control treatment. Four replicate roots were inoculated for each isolate and the control treatment. After inoculation, the roots were misted with sterilized, deionized water, a lid was placed on each bin, and the roots were incubated in the dark at 22°C. Roots were misted daily to maintain high relative humidity. Dark, sunken lesions were first observed 3 days post-inoculation on roots inoculated with the P. sulcatum isolates, and all inoculated roots displayed cavity spot lesions by 7 days. No symptoms were observed on the non-inoculated control roots. Colonies with morphology typical of P. sulcatum were re-isolated from the symptomatic tissue of roots inoculated with the P. sulcatum isolates, and the species identity of the re-isolates was confirmed by ITS rDNA sequence analysis, as described above. Although P. sulcatum is one of several Pythium species that can cause cavity spot of carrot (1), to our knowledge, this is the first report of P. sulcatum causing cavity spot in Washington State, which has the largest acreage of processing carrot crops in the United States (4). References: (1) R. M. Davis and R. N. Raid. Compendium of Umbelliferous Crop Diseases. The American Phytopathological Society, St. Paul, MN, 2002. (2) A. J. van der Plaats-Niterink. Monograph of the Genus Pythium. Stud. Mycol. No. 21. CBS, Baarn, The Netherlands, 1981. (3) K. L. Schroeder et al. Phytopathology 96:637, 2006. (4) E. J. Sorensen. Crop Profile for Carrots in Washington State. U.S. Dept. Agric. National Pest Manage. Centers, 2000.

Over 800 open-pollinated (OP) varieties of sweet corn were grown and named in the century prior to the development of hybrids, but only a few of the historically important OP cultivars exist today. Alleles that could improve disease resistance of modern sweet corn may be present in the OP cultivars still in existence. The objectives of this research were to compare 36 OP sweet corn cultivars to modern commercial hybrids for reactions to Stewart’s wilt, common rust, northern leaf blight (NLB), and southern leaf blight (SLB), and to classify the OP cultivars based on phenotypic reactions to these four diseases. Plants were inoculated in 1994, 1995, and 1996 with Erwinia stewartii, Puccinia sorghi, Exserohilum turcicum, or Bipolaris maydis. Symptoms were rated on a whole-plot basis, and ratings were analyzed by analysis of variance (ANOVA). Means were separated by Bayesian least significant difference values. Some of the OP cultivars had phenotypes that were intermediate to moderately resistant to Stewart’s wilt, common rust, NLB, or SLB, but none of the cultivars were more resistant than the best commercial hybrids. Distributions of ratings for rust, NLB, and SLB were less disperse for the OP cultivars than for commercial hybrids. Hence, the resistance of modern sweet corn germ plasm to Stewart’s wilt, rust, and NLB appears to be greater than that of the OP cultivars. OP cultivars and four standard hybrids were placed into groups based on a hierarchical cluster analysis of disease reactions. The seven groups formed from the cluster analysis of disease ratings were considerably different than those formed from isozyme variation and morphological characteristics. The partial resistance of some cultivars, e.g., Golden Sunshine, Country Gentleman, Stowell’s Evergreen, and Red, may be relatively diverse since these cultivars were placed in different groups based on isozyme and morphological variation. OP cultivars with moderate levels of resistance may be sources of resistance alleles not present in commercial hybrids

In December 2011, symptoms typical of Cladosporium leaf spot caused by Cladosporium variabile (4) were observed in organic “baby leaf” spinach (Spinacia oleracea) crops of the cultivars Amazon, Missouri, Tasman, and Tonga in the Imperial Valley (Imperial County, CA and Yuma County, AZ). Leaves had small, circular lesions (1 to 3 mm in diameter), some of which had progressed to necrotic, bleached lesions surrounded by a thin dark margin. The incidence of symptoms in affected crops was ≤20%. Fungal isolates resembling C. variabile were recovered by surfacesterilizing sections (5 mm2) of symptomatic leaf tissue in 0.6% NaOCl, triple-rinsing the sections in sterile water, and plating the sections onto water agar and potato dextrose agar amended with 100 ppm chloramphenicol (cPDA). Single-spore transfers made onto cPDA were maintained at 24 ± 2°C with a natural day/night cycle. Each isolate produced slow growing cultures consisting of dense masses of dark conidiophores (≤350 μm long) with chains of up to three dematiaceous (olive) conidia, and almost no mycelium. Torulose (coiled) aerial hyphae developed from the apices of conidiophores after 5 to 7 days, and distinguished the isolates as C. variabile, not C. macrocarpum (2,4). Pathogenicity was tested for each of six single-spore isolates using 36-dayold plants of the spinach cultivar Carmel. The plants were enclosed in clear plastic bags overnight and inoculated the next day with the isolates of C. variabile by atomizing approximately 30 ml of a spore suspension (1.0 × 106 conidia/ml in sterile water amended with 0.01% Tween 20) of the appropriate isolate onto the upper and lower leaf surfaces of each of five plants/isolate. Five control plants were inoculated similarly with sterile water + 0.01% Tween 20. The plants were resealed in plastic bags for 72 h and then placed on a greenhouse bench. Pinpoint, sunken lesions developed within 4 to 7 days on the leaves of plants inoculated with each of the six test isolates. Lesions developed into dry, circular spots typical of Cladosporium leaf spot. Symptoms were not observed on control plants. After 20 days, C. variabile was reisolated from lesions caused by all six isolates, but not from control plants. Although Cladosporium leaf spot has been reported in the Salinas Valley of California (4), to our knowledge, this is the first report of the disease on spinach crops in the Imperial Valley of California and Arizona, the primary winter, fresh market spinach production region of the United States. Inoculum of C. variabile may have been introduced to this region on spinach seed lots (3), because even seed infestation levels References: (1) L. J. du Toit et al. Fung. Nemat. Tests 59:V115, 2004. (2) M. B. Ellis. Page 315 in: Dematiaceous Hyphomycetes. Commonwealth Mycological Institute, Surrey, England, 1971. (3) P. Hernandez-Perez. Page 79 in: Management of Seedborne Stemphylium botryosum and Cladosporium variabile Causing Leaf Spot of Spinach Seed Crops in Western Washington, MS thesis, Pullman, WA, 2005. (4) P. Hernandez-Perez and L. J. du Toit. Plant Dis. 90:137, 2006.