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Bacterial blight of carrot (Daucus carota) is caused by Xanthomonas hortorum pv. carotae (4). The pathogen is seed transmitted and carrot seeds can be an important source of primary inoculum (2). A 2008–2009 outbreak of a disease resembling bacterial blight was observed in Mauritius in 10 ha of carrot crops, primarily in humid areas of the island, at an estimated incidence of 10%. Carrot leaves with angular, water-soaked leaf spots that turned necrotic were collected at Plaine Sophie, Mauritius in December 2008. Yellow, Xanthomonas-like colonies were isolated onto KC agar medium (3). MultiLocus sequence analysis (MLSA) with four genes (atpD, dnaK, efp, and gyrB) was performed as described previously (1) on five carrot strains together with two reference strains of X. hortorum pv. carotae (LMG 8643 and LMG 8644). The reference strains were identical. Of the five Mauritius strains, two (LG1-1 and LG1-4) were identical, and most closely related to, but distinct from, the reference strains (genetic distance of 0.02). The other three strains represented two sequence types identified as Xanthomonas sp. based on a phylogenetic tree derived from concatenated sequences, but were not related to any type strain. PCR assays with a 3S primer pair specific for X. hortorum pv. carotae (2) produced an amplicon of approximately 350 bp from isolates LG1-1, LG1-4, and each of the reference strains. A PCR assay with a 9B primer pair (2) yielded an amplicon of 0.9 kb for strains LG1-1, LG1-4, and LMG 8644, whereas LMG 8643 yielded an amplicon of approximately 2.0 kb (2). Foliage of 4-week-old plants (36 plants per strain) of the carrot cv. Senator F1 were spray inoculated with a suspension of each strain using an 18-h culture in sterile 0.01 M tris buffer (pH 7.2) with approximately 1 × 108 CFU/ml. Plants sprayed with tris buffer were used as a negative control treatment. Plants were incubated in a growth chamber at 26 ± 1°C at a relative humidity of 95 ± 5% and a photoperiod of 16 h. Water-soaked lesions that developed into necrotic areas were observed 12 to 15 days after inoculation of LG1-1, LG1-4, and the two reference strains. Bacteria were recovered from lesions onto KC medium (3) 3 weeks after inoculation with mean Xanthomonas populations of at least 1 × 107 CFU/lesion. Colonies with morphology typical of Xanthomonas were recovered and typed using atpD sequencing to fulfill Koch's postulates. Although Xanthomonas-like bacteria were isolated from symptomatic carrot leaves in Mauritius in 1989, the results of that study were not published. To our knowledge, this is the first report of molecular and pathological characterization of this pathogen in carrot crops in Mauritius. References: (1) L. Bui Thi Ngoc et al. Int. J. Syst. Evol. Microbiol. 60:515, 2010. (2) X. Q. Meng et al. Plant Dis. 88:1226, 2004. (3) O. Pruvost et al. J. Appl. Microbiol. 99:803, 2005. (4) L. Vauterin et al. Int. J. Syst. Bacteriol. 45:472, 1995.

Small, black, angular leaf lesions, which sometimes coalesced, were collected from avocado (Persea americana Miller) leaves in a government nursery located at Grand Anse, Mahé, Seychelles archipelago in 2003. Patterns of diseased plants were highly clustered, suggesting local dispersal in the nursery. Yellow-pigmented Xanthomonas-like bacterial colonies were isolated on KC semiselective medium (3). Amplified fragment length polymorphism (AFLP) analysis was performed on two avocado strains together with reference strains of the genetic clusters of Xanthomonas axonopodis (4) and the type strain of all other valid Xanthomonas species using SacI/MspI and four primer pairs (unlabeled MspI + 1 [A, C, T, or G] primers and 5′-labeled – SacI + C primer for the selective amplification step) (1). The two avocado strains showed identical fingerprints and were closely related to X. axonopodis genetic cluster 9.2 (4). One strain, JZ103-1, was further analyzed by MultiLocus Sequence Analysis (MLSA) using portions of three housekeeping genes (atpD, dnaK, and gyrB) as described previously (1). MLSA data confirmed that the xanthomonad associated with avocado was most closely related to X. axonopodis genetic cluster 9.2. No other strain in this genetic cluster shared an identical sequence type. Avocado cv. Grand collet leaves from the youngest growth flush were infiltrated with a needleless syringe (10 inoculation sites per leaf and three replicates) with bacterial suspensions. Typical, water-soaked lesions that developed into black necrotic spots appeared 6 to 8 days after infiltration on all inoculated leaves when suspensions containing ~1 × 106 CFU ml–1 were used (i.e., ~7 × 102 CFU per inoculation site), while no lesions developed on leaves inoculated with Tris buffer or with suspensions containing ~1 × 104 CFU ml–1. One month after inoculation, mean Xanthomonas population sizes determined on KC semiselective medium (3) from ~1 cm2 leaf fragments showing black lesions ranged from 2 × 106 to 4 × 106 CFU per lesion, typical of a compatible interaction. A few colonies that recovered from lesions obtained after inoculation were typed by AFLP and were identical to the inoculated strain. An extensive branch and trunk canker of avocado caused by a Xanthomonas sp. has been reported in California (2). This bacterium did not cause lesions of avocado leaves or fruit after inoculation (2). This appears to be the sole previous report of a xanthomonad being pathogenic to avocado and the symptoms observed in the Seychelles appear therefore very different from the ones reported in California. No major outbreak of bacterial leaf spot of avocado has been reported in the Seychelles archipelago since 2003. References: (1) N. Ah-You et al. Int. J. Syst. Evol. Microbiol. 59:306, 2009. (2) D. A. Cooksey et al. Plant Dis. 77:95, 1993. (3) O. Pruvost et al. J. Appl. Microbiol. 99:803, 2005. (4) J. Rademaker et al. Phytopathology 95:1098, 2005.

Bacterial leaf spot of cucurbits caused by Xanthomonas cucurbitae (4) can be a harmful disease of several cucurbit species in tropical environments, mainly within the Cucumis, Cucurbita, and Citrullus genera. The bacterium induces angular, water-soaked leaf spots, which sometimes become necrotic and have a chlorotic halo. Scab-like lesions on fruit can also be observed (2). Water-soaked, angular leaf lesions were collected from approximately 15 watermelon plants (Citrullus lanatus) in a production field located in Mahé, Seychelles in 2003. Yellow-pigmented Xanthomonas-like bacterial colonies were isolated on KC semiselective medium (yeast extract 7 g, peptone 7 g, glucose 7 g, agar 18 g, distilled water 1,000 ml, propiconazole 20 μg ml–1, cephalexin 40 mg liter–1, and kasugamycin 20 mg liter–1) from all isolation attempts (3). Amplified fragment length polymorphism (AFLP) analysis was performed on four watermelon strains together with reference strains of Xanthomonas cucurbitae (LMG 690 [type strain] and LMG 8663) and the type strain of all other valid Xanthomonas species using SacI/MspI and four primer pairs (unlabeled MspI + 1 [A, C, T, or G] primers and 5′-labeled – SacI + C primer for the selective amplification step) (1). The four strains from watermelon showed identical fingerprints and were most closely related to X. cucurbitae. One strain from diseased watermelon (JZ88-1) was further analyzed by MultiLocus Sequence Analysis (MLSA) using portions of three housekeeping genes (atpD, dnaK, and gyrB) as described previously (1). This strain displayed a very high relatedness (99.8 and 98.9% with strain LMG 690 and LMG 8663, respectively) to the two reference strains of X. cucurbitae. AFLP and MLSA were useful for identifying strains at the species level that were consistent with previous results (1). Bottle-gourd (Lagenaria siceraria), pumpkin (Cucurbita maxima), squash cv. Aurore (Cucurbita pepo), cucumber cv. L-04 (Cucumis sativus), cantaloupe melon cv. Cezanne (Cucumis melo), and watermelon cv. Fou-nan (C. lanatus) leaves were infiltrated (10 inoculation sites per leaf and three replicates) with bacterial suspensions (JZ88-1, LMG 690 and LMG 8663) containing approximately 1 × 105 CFU ml–1 (approximately 1 × 102 CFU per inoculation site). Typical water-soaked lesions that developed into necrotic spots were observed 6 to 8 days after inoculation for all inoculated strains on all inoculated plant species. One month after inoculation, Xanthomonas was recovered from lesions and population sizes determined on KC semiselective medium (3) ranging from 1 × 106 to 9 × 106 CFU per lesion were typical of a compatible interaction. Bacterial leaf spot has appeared sporadically in Mahé, Seychelles since 2003, most often with limited incidence. However, growers need to be aware of the potential negative effect of this disease in tropical environments. References: (1) N. Ah-You et al. Int. J. Syst. Evol. Microbiol. 59:306, 2009. (2) J. F. Bradbury. Page 309 in: Guide to Plant Pathogenic Bacteria. CAB International, Slough, UK, 1986. (3) O. Pruvost et al. J. Appl. Microbiol. 99:803, 2005. (4) L. Vauterin et al. Int. J. Syst. Bacteriol. 45:472, 1995.

In February of 2007, a virus disease survey on tomato plants (Solanum lycopersicum) in greenhouses and open fields was conducted on the island of Mauritius at the request of the Agricultural Research and Extension Unit (AREU), sponsored by the European Union, and funded by the Programme Régional de Protection des Végétaux (PRPV). Yellowing symptoms on the lower and middle leaves of tomato plants and whiteflies (Bemisia tabaci) were observed in greenhouses in Pailles, located in the north region of the island. The interveinal chlorosis pattern of the discolored leaves was similar to symptoms described for Tomato chlorosis virus (ToCV; genus Crinivirus) detected on tomato in 2004 on Reunion Island (1), suggesting the possible involvement of the same virus. Six symptomatic tomato leaf samples were collected from separate plants in the Pailles greenhouses. Total RNA was extracted from these samples with the Qiagen (Courtaboeuf, France) RNeasy Plant Mini Kit. Reverse transcription-PCR was used for molecular diagnosis, independently using two sets of specific ToCV primers. The first set of primers, ToCV-172 and ToCV-610, was designed to amplify the highly conserved region of the heat shock protein 70 (HSP70) gene (2). The second set of primers was designed to amplify the coat protein (CP) gene (forward-CP-ToCV-4384: 5′-ATCCTCTGGTTAGACCGTTAG-3′ and reverse as in Segev et al. [3]). PCR products of the expected size (439 and 725 bp, respectively) were observed for the six samples from the greenhouse from Pailles. For each set of primers, two PCR products obtained from two different samples were cloned using the pGEM-T Easy Vector system (Promega, Madison, WI) and sequenced (Macrogen, Seoul, Korea). The two HSP70 sequences (GenBank-EMBL-DDBJ Accession Nos. AM884013 and AM884014) and the two CP sequences (FM206381 and FM206382) had 100% nucleotide identities (DNAMAN; Lynnon BioSoft, Quebec City, Canada). The highest nucleotide identities of the 439-bp fragment of HSP70 gene (NCBI, BLASTn) were 97% with ToCV isolates from France (DQ355214, DQ355215, and DQ355216), Florida (AY903448), Italy (AM231038 and AY048854), Mayotte Island (AM748818), Portugal (AF234029), and Reunion Island (AM748816). Similarly, the highest nucleotide identities (98%) were obtained with ToCV isolates from France (EU625350) and Spain (DQ136146), with the 725-bp fragments of CP gene. Interestingly, ToCV isolates from Mauritius and Reunion are as divergent as isolates from the rest of the world, which suggests the possibility of different introductions. In conclusion, observed symptoms and laboratory results based on two different regions of the genome confirm the presence of ToCV in symptomatic tomatoes on the island of Mauritius, for the first time to our knowledge. The visual survey carried out in June of 2008 confirmed the presence of typical interveinal chlorosis symptoms in other greenhouses, requiring further studies to assess the incidence of ToCV on tomato crops. References: (1) H. Delatte et al. Plant Pathol. 55:289, 2006. (2) D. Louro et al. Eur. J. Plant Pathol. 106:589, 2000. (3) L. Segev et al. Plant Dis. 88:1160, 2004.