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Fungal plant pathogens can present major problems for most crop species. Currently, control of fungal diseases relies heavily on the use of fungicides. However, there are problems associated with fungicide use, including potential toxicity to non-target organisms and the development of resistance in the target fungus. New strategies are being sought to reduce fungicide use. One area of active research is the potential use of antifungal proteins from various fungal species as alternatives or complements to traditional fungicides. An antifungal protein, Efe-AfpA, from the fungal endophyte Epichloë festucae was previously found to protect plants from the pathogen Clarireedia jacksonii, the causal agent of dollar spot disease. Here we report that Efe-AfpA also has inhibitory activity against other important plant pathogens. These results suggest that it may be possible to develop Efe-AfpA as a biofungicide to target a broad range of destructive plant pathogens. [ABSTRACT FROM AUTHOR]

Anthracnose (Colletotrichum cereale Manns sensu lato Crouch, Clarke & Hillman) has been a devastating disease on annual bluegrass (ABG) [Poa annua L. f. reptans (Hausskn.) T. Koyama] putting green turf over the past 15 yr. The objectives of this 2-yr field trial on ABG were to evaluate the impact of mowing height (2.8, 3.2, and 3.6 mm), mowing frequency (seven and 14 times [wk.sup.-1]), lightweight rolling (none and every other day), and possible interactions of those factors on anthracnose severity and golf ball roll distance (BRD). Mowing height had the greatest effect on anthracnose. Mowing at 2.8 mm increased disease severity 3 to 21% compared with mowing at 3.6 mm, while 3.2 mm was intermediate to higher and lower heights. Mowing frequency had little effect on anthracnose, although mowing 14 times [wk.sup.-1] occasionally reduced disease severity 1 to 14% compared with seven times [wk.sup.-1]. Rolling every other day also occasionally reduced disease severity 5 to 6% under moderate disease pressure. Mowing at 2.8 mm generally provided the greatest BRD. However, similar or greater BRDs were achieved at 3.2 and 3.6 mm, using combinations of increased mowing frequency and/or rolling compared with mowing at 2.8 mm seven times [wk.sup.-1] without rolling. Thus, anthracnose severity on ABG greens can be reduced by raising the mowing height as little as 0.4 mm, and BRD ([greater than or equal to] 2.9-3.2 m) can be maintained by increasing mowing frequency and/or rolling without increasing disease severity.

Dollar spot disease, caused by the fungal pathogen Clarireedia jacksonii, is a major problem in many turfgrass species, particularly creeping bentgrass (Agrostis stolonifera). It is well-established that strong creeping red fescue (Festuca rubra subsp. rubra) exhibits good dollar spot resistance when infected by the fungal endophyte Epichloë festucae. This endophyte-mediated disease resistance is unique to the fine fescues and has not been observed in other grass species infected with other Epichloë spp. The mechanism underlying the unique endophyte-mediated disease resistance in strong creeping red fescue has not yet been established. We pursued the possibility that it may be due to the presence of an abundant secreted antifungal protein produced by E. festucae. Here, we compare the activity of the antifungal protein expressed in Escherichia coli, Pichia pastoris, and Penicillium chrysogenum. Active protein was recovered from all systems, with the best activity being from Pe. chrysogenum. In greenhouse assays, topical application of the purified antifungal protein to creeping bentgrass and endophyte-free strong creeping red fescue protected the plants from developing severe symptoms caused by C. jacksonii. These results support the hypothesis that Efe-AfpA is a major contributor to the dollar spot resistance observed with E. festucae-infected strong creeping red fescue in the field, and that this protein could be developed as an alternative or complement to fungicides for the management of this disease on turfgrasses. [ABSTRACT FROM AUTHOR]

Frequency and severity of anthracnose epiphytotics, caused by Colletotrichum cereale Manns Manns sensu lato Crouch, Clarke, and Hillman, on annual bluegrass (ABG) [Poa annua L. f. reptans (Hauskins) T. Koyama] putting greens have increased over the past decade. This 3-yr field study evaluated the impact of N fertilization (4.9 kg [ha.sup.-1] every 7 or 28 d), mefiuidide (ME; 0 and 0.106 kg a.i. [ha.sup.-1] [yr.sup.-1]) {N-[2,4-dimethyl-5-[[(trifluoromethyl)sulfonyl]amino] phenyl]acetamide}, trinexapac-ethyl (TE; 0 and 0.050 kg a.i. [ha.sup.-1] every 14 d) [4-(cyclopropyl-[alpha]-hydroxymethylene)-3, 5-dioxocyclohexanecarboxylic acid ethylester], verticutting (VC; 0- and 3-mm depth every 14 d), and interactions of these factors on anthracnose of ABG mowed at 3.2 mm. Nitrogen fertilization frequency had the greatest influence on disease throughout the study; N applied at 4.9 kg [ha.sup.-1] every 7 d reduced damage 5 to 24% compared to a 28-d interval. The plant growth regulators, ME and TE, frequently interacted during the last 2 yr of the study; sequential application of ME and TE reduced disease 6 to 14% compared to plots that only received one of these plant growth regulators. At advanced stages of disease, the combination of 7-d N fertilization and ME and TE application had the greatest disease reduction. Verticutting had little effect on anthracnose severity.

Anthracnose disease of cool-season turfgrasses, caused by the fungus Colletotrichum cereale, has recently emerged as one of the most significant pathogens of Poa annua. Here we investigated the utility of four repetitive transposable elements as molecular markers for the analysis of C. cereale populations. Southern blot hybridization analysis revealed lineage-specific polymorphisms and distribution patterns for these transposons. Comparative phylogenetic analysis of three nonrepetitive protein coding DNA sequences against the transposon restriction fragment length polymorphisms indicated that the transposon sequences have similar evolutionary histories to those found in the sampled C. cereale population, despite the alteration of several transposon copies by repeat-induced point mutation. The variability and ubiquity of the [Ccret2.sup.A15] transposon in C. cereale genomes suggest that this element could be used as a reliable DNA marker to discriminate between lineages of the fungus, identify hybrid genotypes, and analyze genetic diversity in populations of this turfgrass pathogen.

Gray leaf spot disease, caused by Pyricularia oryzae Cavara, is an important disease in perennial ryegrass (Lolium perenne L.) turf. Host resistance is an ideal and promising approach to disease control. In this study, two diallel crosses involving six parents and eight parents, respectively, of perennial ryegrass were established to investigate the inheritance of gray leaf spot resistance. Parents and progenies were evaluated for gray leaf spot resistance in growth chamber experiments where they were inoculated with a mixture of five pathogen isolates. A field experiment was conducted on the progenies of one diallel cross. Effects of both general combining ability (GCA) and specific combining ability (SCA) were significant in both growth chamber and field tests. However, the GCA variance accounted for the major portion of the total genotypic variance. Narrow-sense heritability calculated by midparent-offspring regression ranged from 0.57 to 0.76, indicating additive gene effects were the major genetic component in control of gray leaf spot. Estimates of minimum number of genes ranged from 2.1 to 4.4, suggesting resistance to gray leaf spot was controlled by a small number of genes. All the results suggested that a breeding program basing on recurrent selection should be effective to improve the resistance to gray leaf spot in perennial ryegrass., GRAY LEAF SPOT has rapidly become one of the most important diseases of perennial ryegrass (Lolium perenne L.) in United States since its identification (Dernoeden, personal communications, 1986; Landschoot and [...]

Gray leaf spot, caused by the fungus Pyricularia grisea (Cooke) Sacc. [teleomorph Maguaporthe grisea (T.T. Herbert) Yaegashi & Udagawa], can be a devastating disease on perennial ryegrass (Lolium perenue L.). The identification and utilization of perennial ryegrass cultivars with improved resistance to gray leaf spot would reduce the need for fungicide applications. The objectives of this study were to: (i) evaluate cultivars, experimental selections, and single-plot progenies of perennial ryegrass for resistance to gray leaf spot, (it) develop populations from selected resistant parents to determine improvements in the next generation, and (iii) determine heritability and the response to selection for gray leaf spot resistance in perennial ryegrass populations. Two perennial ryegrass field experiments consisting of commercial cultivars and experimental selections, were established in 2000 and 2001 at Adelphia, NJ. Susceptibility of germplasm to gray leaf spot was evaluated following ephemeral natural outbreaks of the disease that occurred three to four weeks post seeding. Parents with improved resistance to gray leaf spot were selected based on progeny turf plot evaluations in 2000, inter-pollinated and seeded into turf plots in the 2001 experiment. Most cultivars and selections evaluated in both experiments had greater than 50% gray leaf spot disease. The high broad-sense heritability estimate (0.92) and similar response of progeny compared to selected parents indicated that parent selection based on progeny tests was a good selection method to predict the combining ability of the parents. It also proved successful in improving gray leaf spot resistance in the next generation, which will be important for the development of more disease resistant cultivars., GRAY LEAF SPOT has become a significant pathogen of perennial ryegrass. Pyricularia grisea was first associated with foliar blighting of perennial ryegrass in 1985 (Dernoeden, 1996), but was not confirmed [...]

Dollar spot (Clarireedia jacksonii) susceptibility varies among bentgrasses (Agrostis spp.). This trial assessed the ability of five action thresholds of the risk index (RI) of a logistic regression model to forecast dollar spot incidence on bentgrass fairway turf grown on a sandy loam in North Brunswick, NJ. Dollar spot incidence was assessed over 128 observation periods (May to Nov. annually) over 3 yr and related to five action thresholds for prediction accuracy. Action thresholds included a RI threshold of 20% (RI 20%), interpreting the change in the RI over time (RI slope), adjusting the RI upwards to maximize accuracy (RImax), combining RI 20% with RI slope, and combining RImax with RI slope. The RI 20% accurately predicted disease on 63 to 66% of observation periods for highly susceptible creeping bentgrass (A. stolonifera L.) cultivars Shark, Penncross, and Independence; other action thresholds improved accuracy by only 10% or less for these cultivars. Prediction accuracy on lower susceptibility cultivars (007, Declaration, and colonial bentgrass Capri; A. capillaris L.) was substantially improved with four novel action thresholds by reducing over‐predictions compared to RI 20%. Accuracy was improved by as much as 32% when the RImax and RI slope were combined for Declaration compared to RI 20%. On low susceptibility cultivars, turf managers may be able to use action thresholds that incorporate a RI greater than 20% and/or RI slope to reduce fungicide inputs and maintain acceptable dollar spot control compared to RI 20%. Core Ideas: A 20% RI threshold over‐predicted dollar spot on low susceptibility cultivars. Thresholds using a RI >20% or RI slope improved accuracy for low susceptibility cultivars. Novel action thresholds may reduce fungicide inputs on low susceptibility cultivars. ​ [ABSTRACT FROM AUTHOR]

Mechanical injury from cultivation practices is reported to enhance anthracnose disease, caused by the fungus Colletotrichum cereale Manns sensu lato Crouch, Clarke, and Hillman, of annual bluegrass (ABG) [Poa annua L. forma reptans (Hausskn.) T. Koyama]. Two field experiments were initiated with the objectives of determining the effects of midseason cultivation practices (Experiment 1) and scarifying depth (Experiment 2) on anthracnose severity of ABG maintained at a 3.2‐mm mowing height on a Nixon sandy loam in North Brunswick, NJ. Experiment 1 treatments consisted of grooming, verticutting, scarifying, and solid‐tining every 21 d as well as weekly grooming and no cultivation over 2 years. Experiment 2 evaluated single treatments of shallow and deep scarifying and a nontreated control in three runs. Verticutting increased the area under the disease progress curve (AUDPC) compared with no cultivation during the first year, whereas verticutting and scarifying increased AUDPC relative to no cultivation during the second year. No other cultivation treatments differed from the control during either year in Experiment 1. In Experiment 2, scarifying did not increase AUDPC during any run at either depth. Results from these experiments indicate that cultivation practices that affect at least 15% of the turf surface area and injure crowns may increase anthracnose severity, whereas practices that affect a smaller turf area or only leaf tissue will not increase disease severity. [ABSTRACT FROM AUTHOR]

Potassium fertilization can improve stress tolerances in turfgrass; however, its effect on turfgrass diseases is inconsistent and not well understood. A 3-yr field study was initiated to determine the effect of K fertilization rate and K source on anthracnose disease of annual bluegrass turf. Potassium chloride and K2SO4 were applied at K rates of 54, 109, and 218 kg ha-1 yr-1 as a 2 x 3 factorially arranged randomized complete block design with four replications. Potassium nitrate and K2CO3 were also included at the 218 kg K ha-1 yr-1 rate, as well as an untreated check. Nonlinear regression models were used to estimate critical concentrations of K in the mat layer and tissue with respect to anthracnose severity. All K treatments reduced disease severity compared to the untreated check (no K); however, KCl was less effective than the other sources when applied at the 218 kg K ha-1 yr-1 rate. The Cate--Nelson regression model predicted that K values less than 43 mg kg-1 in the mat layer (Mehlich 3 extractant) and 20 g kg-1 in leaf tissue will increase anthracnose severity of annual bluegrass (ABG). This study provides evidence that K fertilization can reduce anthracnose severity and that the severity of this disease can be correlated with mat and tissue K concentrations. Thus, it is important to monitor K in ABG turf and to maintain sufficient levels to reduce disease severity and improve turfgrass quality. [ABSTRACT FROM AUTHOR]

Sand topdressing applied to annual bluegrass [Poa annua L. f. reptans (Hausskn.) T. Koyama] putting greens during the spring and summer can reduce anthracnose caused by Colletotrichum cereale Manns sensu lato Crouch, Clarke, and Hillman. However, the effects of autumn topdressing on this disease and the annual quantity of sand required to suppress anthracnose are not known. A 3-yr field study was initiated in 2010 to evaluate a 3 x 3 x 3 factorial of autumn, spring, and summer topdressing on anthracnose severity of annual bluegrass maintained at 2.8 mm. Autumn and spring topdressing was applied at 0, 1.2, or 2.4 L m-2 yr-1 and 0, 0.6, or 1.2 L m-2 yr-1 of sand was applied during summer. Linear and Cate-Nelson models were used to evaluate the response of anthracnose to annual topdressing quantity. Spring topdressing caused the greatest reduction in disease. Autumn topdressing reduced disease early each year following application, while spring topdressing provided consistent disease suppression throughout the growing season. Summer topdressing rates, similar to those applied on golf courses, reduced disease only in 2012 (mid- to late summer). Additionally, modeling the disease response against annual topdressing quantity indicated that increasing topdressing up to 6.0 L m-2 yr-1 produced a linear reduction of anthracnose on annual bluegrass. Golf turf managers should recognize that autumn topdressing will aid in anthracnose suppression; however, spring applications are more effective when anthracnose is the management objective. [ABSTRACT FROM AUTHOR]

Anthracnose (caused by Colletotrichum cereale Manns sensu lato Crouch, Clarke & Hillman) of annual bluegrass [ABG, Poa annua L. f. reptans (Hausskn.) T. Koyama] turf is a destructive fungal disease that has been shown to be more severe under nitrogen (N) deficiencies. Little is known about the effect of soluble N source on this disease. A 3-yr field study was initiated in 2010 to evaluate the effect of soluble N source on anthracnose severity and to determine if N source alters the effect of N frequency on this disease during midseason on an ABG turf maintained at 3.2 mm. Nitrogen treatments were applied at 4.9 kg N ha-1 every 7 or 14 d (frequency factor) as solutions of ammonium sulfate, ammonium nitrate, urea, calcium nitrate, or potassium nitrate. Both N frequency and N source affected disease severity throughout 2010, 2011, and 2012. In general, soluble N applied at 4.9 kg N ha-1 every 7 d reduced disease compared with N applied at the same rate every 14 d. Of the N sources, potassium nitrate provided the greatest reduction in disease severity over the 3-yr study, whereas ammonium sulfate treatments resulted in the greatest disease severity. Soil pH was also influenced by N source, with ammonium sulfate treatments resulting in the lowest soil pH (most acidic), and potassium nitrate consistently producing the highest soil pH (most basic) throughout the study. Potassium nitrate also greatly increased soil K. This study has shown that anthracnose severity on ABG putting green turf is influenced by N source, and that low-rate applications of potassium nitrate every 7 d were most effective at reducing disease severity under moderately acidic soil conditions and moderate to low soil K levels. [ABSTRACT FROM AUTHOR]

There is increasing interest in understanding plant-associated microbial communities and their impact on plant health. However, research has been limited to major agronomic systems and little is known about the resident microorganisms in economically important specialty crops, such as turfgrass. In this study, we generated a community-wide inventory of the archaea and bacteria that inhabit the soil of Poa annua L. putting green turf at five time points over a 1-yr period. Next-generation sequencing of the nuclear ribosomal DNA 16S revealed 1.5 ' 105 unique operational taxonomic units from 25 pooled soil samples. Seventeen archaeal taxa were identified at the species level, 53% of which were members of the Crenarchaeota. Proteobacteria was the most abundant bacterial phylum, comprising 36% of the 442 taxa present. Distance analysis and analysis of similarities revealed that the archaeal and bacterial communities clustered according to sample date, with samples collected during warm months grouping separately from those collected during cool months. Clustering was less distinct when plotted using detrended correspondence analysis. These data indicate that microbial community structure varied throughout the growing season, possibly due to seasonal changes in temperature and/or other environmental factors. This research also shows that P. annua putting green turf supports a diverse microbial community despite management practices that include frequent pesticide applications. [ABSTRACT FROM AUTHOR]

Increased N fertilization, mowing height, and sand topdressing are management practices that can suppress anthracnose disease of annual bluegrass [Poa annua L. f. reptans (Hausskn) T. Koyama; ABG] caused by Colletotrichum cereale Manns. A 3-yr field study evaluated the relative importance and interactions of these factors on anthracnose severity, turfgrass quality, and ball roll distance (BRD) on ABG turf in North Brunswick, NJ. A factorial combination of mowing height (2.3 and 3.2 mm), N fertilization (100 and 200 kg ha-1 yr-1), and sand topdressing (46 and 98 Mg ha-1 yr-1 in 2012; 37 and 81 Mg ha-1 yr-1 during 2013 and 2014) was arranged in a split-split-plot design with four replications. The practice of applying greater N fertilization (200 kg ha-1) provided the greatest reduction in disease severity and improvement in quality than the practices of higher mowing (3.2 mm) or greater sand topdressing (98 or 81 Mg ha-1). Combining greater N with higher mowing and greater sand topdressing provided acceptable disease suppression without the use of fungicides during moderate but not severe anthracnose epidemics. Higher mowing often produced unacceptable BRD (<2.9 m) especially when combined with greater N fertilization; whereas, under lower mowing, BRD was acceptable on most observation dates (91-96%) and less influenced by greater N fertilization. Thus, when adjustments in best practices for anthracnose management are needed to enhance BRD; lowering the mowing height will provide that enhancement while not greatly increasing the risk for anthracnose especially when greater N and increased topdressing practices are also employed. [ABSTRACT FROM AUTHOR]

Sand topdressing annual bluegrass [Poa annua L. f. reptans (Hausskn) T. Koyama] (ABG) turf during the summer (SU) can reduce the severity of anthracnose disease, caused by Colletotrichum cereale Manns, but the effect of spring (SP) topdressing warrants further research. A 2-yr field study evaluated the effect of SP and SU topdressing on anthracnose severity of ABG maintained at 3.2-mm on a sandy loam in North Brunswick, NJ. Factors of SP (0, 1.2, and 2.4 L m-2 yr-1) and SU (0, 0.525, 1.05, 2.1, and 4.2 L m-2 yr-1) topdressing rate were arranged as a 3 × 5 factorial. Increasing SP rate reduced the area under disease progress curve (AUDPC) linearly in both years, whereas increasing SU rate reduced AUDPC linearly in 2009 but quadratically in 2010. Maximum AUDPC reduction was predicted at a lower total topdressing rate (2.4 and 2.63 L m-2 yr-1 during SP and SU, respectively) in 2010 than 2009. Unlike AUDPC data, pooled disease severity data indicated that SP interacted with SU topdressing, and by late 2010, a SU topdressing rate as low as 2.1 L m-2 yr-1 (at the greatest SP rate) maximized disease suppression. However, incorporation of sand applied at 2.1 and 4.2 L m-2 yr-1 was often delayed, resulting in excess sand on the surface, whereas lower SU rates (0.525 and 1.05 L m-2 yr-1) readily incorporated into the turf. This research indicates that SP topdressing can be used to reduce the rate of SU topdressing needed to suppress anthracnose but may not eliminate the need for SU topdressing to maximize disease suppression. [ABSTRACT FROM AUTHOR]

Colletotrichum cereale is an ascomycete inhabitant of cool-season Pooideae grasses. The fungus has increased in frequency over the past decade as a destructive pathogen of Poa annua and Agrostis stolonifera turfgrass. Colletotrichum cereale exists as two lineages, designated clades A and B, but little is known about the distribution of these clades in natural environments, or what role these subdivisions may play in the trajectory of disease outbreaks. In this study, our objective was to determine the frequency of C. cereale clades A and B. To rapidly discriminate between the two C. cereale clades, a real-time PCR assay was developed based on the Apn2 gene. A collection of 700 C. cereale pathogens and endophytes from twenty Pooideae grass genera were genotyped. 87% of the collection was identifed as part of clade A, 11.7% as part of clade B, and 1.3% was a mixture. Colletotrichum cereale from turfgrass hosts in North America were most commonly members of clade A (78%). The overabundance of clade A in turfgrass isolates was directly attributable to the dominance of this lineage from southern sampling sites, irrespective of host. In contrast, 111 C. cereale turfgrass isolates collected from northern sampling sites were evenly distributed between clades A and B. Only 28% of C. cereale from A. stolonifera at northern sampling sites were part of clade A. These data show that environmental factors such as geographic location and host identity likely played a role in the distribution of the major C. cereale clades in North American turfgrass. [ABSTRACT FROM AUTHOR]

Lightweight rolling can be effectively used to increase ball roll distance (BRD) and influence anthracnose development on annual bluegrass (ABG) \Poa annua L. f. reptans (Hausskn) T. Koyama] putting green turf. The objective of this 3-yr field trial was to evaluate the influence of roller type (i.e., sidewinder, triplex mounted vibratory, and nonrolled) and location (center or perimeter) of equipment traffic on anthracnose severity, turf quality, and BRD of ABG turf maintained at 3.2 mm. Both roller types either had no effect or reduced disease 3 to 13% compared to nonrolled turf under moderate disease pressure in 2006,2007, and 2008. Disease severity was not different between the roller types on most dates; however, the heavier sidewinder roller did result in less disease than the triplex mounted vibratory roller on 4 of 13 rating dates in 2007 and 2008. Interestingly, perimeter plots had slightly less disease compared to center plots on 6 of 13 rating dates. The current study shows that the practice of rolling does not explain field observations that greater anthracnose can often occur and is most severe within the perimeter of putting greens. Alternatively, this research indicates that rolling can be used to increase BRD and improve turf quality without exacerbating the severity of anthracnose disease on ABG putting green turf. [ABSTRACT FROM AUTHOR]

Sand topdressing has been reputed to increase anthracnose caused by Colletotrichum cereale Manns sensu lato Crouch, Clarke, and Hillman on annual bluegrass (ABG) [Poa annua L. forma reptans (Hausskn.) T. Koyama] putting greens. Field trials were conducted to determine the effects of (i) frequent (7 d) and low-rate (0.3 L m-2) sand topdressing and brushing, (ii) infrequent (21 and 42 d) and increased-rate (1.2 L m-2) sand topdressing, and (iii) sand topdressing application intervals (7,14, and 28 d) and rates (0.3 and 0.6 L m-2) on anthracnose severity of ABG turf mowed at 3.2 mm. Topdressing every 7 d at 0.3 L m-2 initially enhanced disease (8%) during the first year of the trial; however, continued topdressing reduced anthracnose severity 17 to 47% later in 2006 and 3 to 26% in 2007 compared to nontopdressed turf. Topdressing every 21 and 42 d at 1.2 L m-2 reduced disease 4 to 28% over the 2-yr study; however, sand applied every 21 d reduced disease 5 to 13% more than the 42-d interval in 2007. Topdressing rate (0, 0.3, and 0.6 L m-2) and interval (7, 14, and 28 d) interacted to affect anthracnose severity in both years. Disease declined in a curvilinear manner as rate increased at the 7 and 14-d intervals each year. Increased rates applied every 28 d reduced disease linearly in 2006 and curvilinearly at rates exceeding 0.3 L m-2in 2007. Topdressing every 7 or 14 d at 0.3 or 0.6 L m-2, respectively, provided the most rapid and effective anthracnose reduction and best turf quality. [ABSTRACT FROM AUTHOR]

Irrigation can influence both turf vigor and play-ability of putting greens. Anthracnose (Colletotrichum cereale Manns sensu lato Crouch, Clarke, and Hillman) has become an increasingly destructive disease of annual bluegrass (ABG) [Poa annua L. f. reptans (Hausskn.) T. Koyama] putting greens, particularly when turf is under stress. This 3-yr field study evaluated the effects of irrigation quantity (100, 80, 60, and 40% of reference evapotranspiration [ETJ) on anthracnose severity of ABG mowed daily to 3.2 mm. Severe drought stress (40% ET0) increased anthracnose severity in 2006, 2007, and 2008. Anthracnose was less severe under 60% ET0 irrigation, and irrigating at 80% ET0 reduced severity compared to 60% ET0. Irrigating at 100% ET0 initially reduced anthracnose sever- ity compared to 40% ET0 however, 100% El0 resulted in similar disease severity later in the 2006 and 2008 seasons. While this response was not observed late in the 2007 season, plots maintained at 100% ET0 had turf quality similar to plots irrigated at 40% ET0 later in each year due in part to increased algal development. Irrigation to replace 80% ET0 typically resulted in the least amount of disease and the best turf quality throughout the trial. Thus, irrigation to minimize drought stress while also avoiding continuous high soil water content is beneficial in reducing anthracnose and maintaining acceptable turf performance. [ABSTRACT FROM AUTHOR]

Field trials at two locations in Norway previously demonstrated differences in winter survival between two Agrostis species used for turf, velvet bentgrass (VB; A. canina L.) and creeping bentgrass (CB; A. stolonifera L.). The objectives of this study were to compare freezing tolerance and crown carbohydrate composition of VB and CB. We also compared a direct and two indirect methods of measurements of freezing tolerance. Treatments consisted of: (i) nonacclimated (NA); (ii) acclimation at 2°C for 2 wk (A2); (iii) acclimation at 2°C for 4 wk (A4); and (iv) acclimation at 2°C for 4 wk plus subzero acclimation at -2°C for 2 wk (A4+SZA2). Crowns were harvested for determination of carbohydrates and freezing tolerance. Freezing tolerance (lethal temperature for 50% of the test population [LT50]) was based on whole plant survival (WPS), 2,3,5-tn- phenyltetrazolium chloride (TTC) reduction, and electrolyte leakage (EL). There was no significant difference in freezing tolerance between VB and CB. The LT50 based on WPS was significantly lower for plants exposed to A2 (-12.7°C), A4 (-14.5°C), and A4+SZA2 (-14.6°C) compared to the NA control treatment (-8.4°C). The concentrations of fructans and sucrose were significantly higher in A2 compared to NA plants of both species, but only fructans continued to increase at A4. The LT50 based on TTC reduction showed better correlation with LT50 based on WPS compared to LT50 values based on EL. [ABSTRACT FROM AUTHOR]

Over the past decade, the emergence of anthracnose disease has newly challenged the health of turfgrasses on North American golf courses, resulting in considerable economic loss. The fungus responsible for the outbreaks, Colletotrichum cereale, has also been identified from numerous natural grasses and cereal crops, although disease symptoms are generally absent. Here we utilize phylogenetic and population genetic analyses to determine the role of ecosystem in the advancement of turfgrass anthracnose and assess whether natural grass and/or cereal inhabitants are implicated in the epidemics. Using a four-gene nucleotide data set to diagnose the limits of phylogenetic species and population boundaries, we find that the graminicolous Colletotrichum diverged from a common ancestor into distinct lineages correspondent with host physiology (C3 or C4 photosynthetic pathways). In the C4 lineage, which includes the important cereal pathogens Colletotrichum graminicola, C. sublineolum, C. falcatum, C. eleusines, C. caudatum and several novel species, host specialization predominates, with host-associated lineages corresponding to isolated sibling species. Although the C3 lineage — C. cereale— is comprised of one wide host-range species, it is divided into 10 highly specialized populations corresponding to ecosystem and/or host plant, along with a single generalist population spread across multiple habitat types. Extreme differentiation between the specialized C. cereale populations suggests that asymptomatic nonturfgrass hosts are unlikely reservoirs of infectious disease propagules, but gene flow between the generalist population and the specialized genotypes provides an indirect mechanism for genetic exchange between otherwise isolated populations and ecosystems. [ABSTRACT FROM AUTHOR]

The article profiles several college teachers. Professor Bruce B. Clarke of the Rutgers University focused his research program on the etiology and control of turfgrass disease and integrated pest management strategies to reduce fungicide use. USDA-ARS Plant Sciences Institute director Wanda Collins focused on genetics and germplasm resources and tuber crops. Roch E. Gaussoin, professor of agronomy and horticulture, focuses on turfgrass weed management and the management and construction of golf greens.

Over the past several decades, breeding cool-season turfgrasses for improved disease resistance has been the focus of many turfgrass breeding programs. This review article discusses the dramatic improvements made in breeding Kentucky bluegrass (Pot pratensis) for resistance to leaf spot (caused by Drechslera poae), stem rust (caused by Puccinia graminis), and stripe smut (caused by Ustilago striiformis); perennial ryegrass (Lolium perenne) for resistance to gray leaf spot (caused by Pyricularia grisea), stem rust and crown rest (caused by Puccinia coronata); tall fescue (Festuca arundinacea) for resistance to brown patch (Rhizoctonia solani) and stem rust; creeping bentgrass (Agrostis stolonifera) for resistance to dollar spot (caused by Sclerotinia homoeocarpa); and fine rescues (Festuca spp.) for improved disease resistance. Historically, the dramatic improvements in disease resistance of the cool-season grasses have been attributed to traditional/ conventional breeding techniques; however, it is likely that functional genomics and molecular techniques will play a more significant role in the development of cultivated turfgrasses as the specific genes and mechanisms for disease resistance are identified in the future. [ABSTRACT FROM AUTHOR]

In 1989, a close association was found between single-plant progenies of strong creeping red rescue infected with the endophyte Epichloü festucae and enhanced suppression of dollar spot, a widespread foliar disease of turfgrass caused by Sclerotinia homoeocarpa. From this limited observation, extensive field evaluations were conducted on a wide range of fine rescue germplasm obtained throughout the United States and Europe to determine the frequency and magnitude of this association. In five field trials established between 1985 and 1991, endophyte-infected Chewings, hard, blue, and strong creeping red rescue cultivars, selections, and crosses consistently exhibited endophyte-mediated suppression of dollar spot, when compared with closely related endophyte-free entries. Endophyte-infected Chewings and hard rescue cultivars and selections also had greater turf density and supported less foliar mycelium of S. homoeocarpa than endophyte-free entries. [ABSTRACT FROM AUTHOR]

Gray leaf spot disease, caused by Pyricularia oryzae Cavara, is an important disease in perennial ryegrass (Lolium perenne L.) turf. Host resistance is an ideal and promising approach to disease control. In this study, two diallel crosses involving six parents and eight parents, respectively, of perennial ryegrass were established to investigate the inheritance of gray leaf spot resistance. Parents and progenies were evaluated for gray leaf spot resistance in growth chamber experiments where they were inoculated with a mixture of five pathogen isolates. A field experiment was conducted on the progenies of one diallel cross. Effects of both general combining ability (GCA) and specific combining ability (SCA) were significant in both growth chamber and field tests. However, the GCA variance accounted for the major portion of the total genotypic variance. Narrow-sense heritability calculated by midparent-offspring regression ranged from 0.57 to 0.76, indicating additive gene effects were the major genetic component in control of gray leaf spot. Estimates of minimum number of genes ranged from 2.1 to 4.4, suggesting resistance to gray leaf spot was controlled by a small number of genes. All the results suggested that a breeding program basing on recurrent selection should be effective to improve the resistance to gray leaf spot in perennial ryegrass. [ABSTRACT FROM AUTHOR]

Colletotrichum species cause anthracnose diseases on a number of grass hosts and are common inhabitants of many others. They are divided into four species: C. sublineolum is pathogenic to Sorghum spp., C. caudatum is found on C4 grasses such as indiangrass and big bluestem; C. falcatum causes red rot of sugarcane; and C. graminicola sensu lato is a broadly defined species including isolates that attack maize, wheat, oats, and many forage, tuff, and amenity grasses of the subfamily Pooideae. In this paper, a combination of hierarchal- and nonhierarchal-based analyses were employed to examine evolutionary relationships among the grass-infecting Colletotrichum species, with special emphasis on isolates from turf and other grasses in the subfamily Pooideae. Reconstructions performed with data sets from over 100 Colletotrichum isolates at three variable loci using phylogenetic and network-based methodologies unambiguously supported the taxonomic separation of maize-infecting isolates of C. graminicola from the pooid-infecting strains of Colletotrichum. To reflect the evolutionary relationships that exist between these distinct lineages, we propose the resurrection of the species name C. cereale to describe the pooid-infecting isolates. There was also support for further subdivision of C. cereale, but the current data arc insufficient to confidently subdivide the species, as there was some evidence of recombination between lineages of this species. [ABSTRACT FROM AUTHOR]

This report analyzes the sources and nature of disputes/conflicts. It attempts to develop a model that allows one to categorize where one is in the development of a conflict. Within the discussion of this model, particular attention is devoted to hostilities and terminating a conflict on favorable terms. The key concept is that of incompatible national objectives. This incompatibility may lead to hostilities in which the aim is to apply military economic, and political power in such a manner as to cause one opponent to change his political objectives to accommodate the others. The thrust of this report is the need to determine how to induce either the leader or some chosen political group in the opponent's government to want to change that nation's objectives so that the source of the conflict is eliminated, and then to take actions that cause that faction to have both the desire and ability to influence that change in objectives to occur. The analysis suggests that victory will result from the successful defense of one's own political and military centers of gravity combined with action that, at least indirectly, threat- ens the opponent's center(s) of gravity with the result being a change in objectives. The report examines the constraints that inhibited U. S. activities in the international arena prior to the end of the cold war It concludes with a rational decision making approach that establishes, and then seeks to achieve, "victory criteria." The author contends that the key to this process is the development of three critical pieces of guidance: (1) A clear statement by the political authorities of the desired situation in the post-hostility and settlement phases-a vision of what the area should "look like "following the hostilities; (2) a clear set of political objectives that when achieved will allow the above vision to become reality: and (3) a set of military objectives that will, when achieved, allow the above to happen. [ABSTRACT FROM AUTHOR]

Strong creeping red fescue (Festuca rubra subsp. rubra) is a commercially important low-maintenance turfgrass and is often naturally infected with the fungal endophyte Epichloëfestucae. Epichloë spp. are endophytes of several cool-season grass species, often conferring insect resistance to the grass hosts due to the production of toxic alkaloids. In addition to insect resistance, a unique feature of the strong creeping red fescue/E. festucae symbiosis is the endophyte-mediated disease resistance to the fungal pathogen Clarireedia jacksonii, the causal agent of dollar spot disease. Such disease resistance is not a general feature of other grass/ Epichloë interactions. E. festucae isolates infecting red fescue have an antifungal protein gene Efe-afpA, whereas most other Epichloë spp. do not have a similar gene. The uniqueness of this gene suggests it may, therefore, be a component of the unique disease resistance seen in endophyte-infected red fescue. Here, we report the generation of CRISPR-Cas9 Efe-afpA gene knockouts with the goal of determining if absence of the protein in endophyte-infected Festuca rubra leads to disease susceptibility. However, it was not possible to infect plants with the knockout isolates, although infection was possible with the wild type E. festucae and with complemented isolates. This raises the interesting possibility that, in addition to having antifungal activity, the protein is required for the symbiotic interaction. The antifungal protein is a small secreted protein with high expression in planta relative to its expression in culture, all characteristics consistent with effector proteins. If Efe-AfpA is an effector protein it must be specific to certain interactions, since most Epichloë spp. do not have such a gene in their genomes. [ABSTRACT FROM AUTHOR]

Many cool-season grasses have symbiotic relationships with Epichloë (Ascomycota, Clavicipitaceae) fungal endophytes that inhabit the intercellular spaces of the above-ground parts of the host plants. The presence of the Epichloë endophytes is generally beneficial to the hosts due to enhanced tolerance to biotic and abiotic stresses conferred by the endophytes. Many Epichloë spp. are asexual, and those infections always remain asymptomatic. However, some Epichloë spp. have a sexual stage and produce a macroscopic fruiting body, a stroma, that envelops the developing inflorescence causing a syndrome termed "choke disease". Here, we report a fungal and plant gene expression analysis of choke stroma tissue and asymptomatic inflorescence tissue of Epichloëfestucae-infected strong creeping red fescue (Festuca rubra subsp. rubra). Hundreds of fungal genes and over 10% of the plant genes were differentially expressed when comparing the two tissue types. The differentially expressed fungal genes in the choke stroma tissue indicated a change in carbohydrate and lipid metabolism, as well as a change in expression of numerous genes for candidate effector proteins. Plant stress-related genes were up-regulated in the stroma tissue, suggesting the plant host was responding to the epiphytic stage of E. festucae as a pathogen. [ABSTRACT FROM AUTHOR]

Sand size can affect the ability to incorporate topdressing into the turf canopy and thatch on golf course putting greens; unincorporated sand interferes with mowing and play. This 3-year field trial was initiated to determine the effects of sand size on sand incorporation, surface wetness, and anthracnose (caused by Colletotrichum cereale Manns sensu lato Crouch, Clarke, and Hillman) of annual bluegrass [Poa annua L. f. reptans (Hausskn) T. Koyama] maintained as a putting green. The experimental design was a randomized complete block with four replications; treatments included a non-topdressed control and three topdressing sands (medium-coarse, medium, or medium-fine) applied every 2 weeks at 0.15 L⋅m-2 during the summer. Topdressing with medium-coarse sand was more difficult to incorporate than the medium and medium-fine sands, resulting in a greater quantity of sand collected with mower clippings. Analyzing the particle distribution of sand removed by mowing confirmed that coarser sand particles were more likely to be removed in mower clippings. Surface wetness measured as volumetric water content (VWC) at the 0- to 38-mm depth zone was greater in non-topdressed plots than topdressed plots on 35% of observations. Few differences in VWC were found among sand size treatments. Turf responses to topdressing were not immediate; however, as sand accumulated in the turf canopy, topdressed plots typically had lower anthracnose severity than non-topdressed turf after the first year. Additionally, topdressing with medium and medium-fine sands produced similar or occasionally lower disease severity than topdressing with medium-coarse sand. The lack of negative effects of medium and medium-fine sands combined with better incorporation after topdressing and less disruption to the putting surface should allow golf course superintendents to apply topdressing at frequencies and/or quantities needed during the summer to maintain high-quality turf and playing conditions. [ABSTRACT FROM AUTHOR]

A field day event was used to demonstrate the value of proper pesticide application methods to turfgrass. A single fungicide was applied through four nozzle-types and four water-carrier volumes targeting a common foliar disease in turfgrass. Most golf course superintendents surveyed use the same nozzle-type for all pesticide applications, but this field study indicated better disease control from the fungicide applied through certain nozzle-types and water-carrier volumes. As a result, most superintendents intended to make improvements to their pesticide application programs, and many had a highly favorable view of including this type of research at future field day events. [ABSTRACT FROM AUTHOR]

Rusts are destructive fungal diseases that can cause severe thinning and unattractive discoloration of kentucky bluegrass (KBG; Poa pratensis L.). Currently, turfgrass breeding programs rely on field evaluations to screen KBG germplasm for rust resistance; methods that are expensive, labor intensive, and require large turf areas. The availability of a greenhouse-based assay to perform prescreening of KBG germplasm for resistance to rust diseases before field trials would allow breeders to remove the poorest performing plants before field evaluations thus enhancing breeding efficiency. In this study, we set out to develop a reliable, low-cost greenhouse inoculation protocol for the two most common rust pathogens of KBG in temperate growing regions: Puccinia coronata and Puccinia graminis, the causal agents of crown and stem rust, respectively. Using a modified inoculation assay and custom-built plexi-glass chambers adapted from protocols used for cereal rust pathogens, urediniospores of crown and stem rust fungi developed on inoculated plants 10 to 14 days postinoculation. Real-time polymerase chain reaction (PCR) assays, disease symptomology, and morphology of urediniospores confirmed the presence and identity of both rust pathogens from inoculated host tissue. The inoculation protocols described here represent an effective method to accelerate screening of KBG germplasm for resistance to crown and stem rust diseases. Infection of KBG plants in the greenhouse will also allow breeders to maintain populations of crown and stem rust fungi throughout the year, providing a reliable and ongoing source of pathogen inoculum for experimentation and screening in the future. [ABSTRACT FROM AUTHOR]

Over the past 10 years, rust diseases have become increasingly prevalent on certain cultivars of Kentucky bluegrass. This pattern suggests that new races or new species of rust fungi may have emerged. To test this hypothesis, 66 samples of turfgrass rust fungi collected from across the United States were evaluated based on sequences of the internal transcribed spacer (ITS)-5.8S rDNA region. Phylogenetic analysis revealed three species: Puccinia coronata, P. graminis, and P. striiformis, comprising 67, 28, and 5% of the samples, respectively. P. coronata was frequently found in association with Kentucky bluegrass, a host-pathogen relationship that has not been previously reported. Comparison of molecular analyses with the use of standard field identification techniques-host association and pustule pigmentation-showed that 58% of the Kentucky bluegrass samples would have been incorrectly diagnosed using nonmolecular criteria. To avoid such misidentifications, a real-time polymerase chain reaction diagnostic protocol was developed for turfgrass-associated P. graminis, P. coronata, and P. striiformis using ITS sequences. Accurate, reproducible, species-specific identifications were made using as few as 50 to 150 urediniospores, even in mixed infections. This study represents the first DNA-based evaluation of turfgrass rust fungi and provides a quick and reliable sequence-based protocol as an alternative to less reliable field-based identification techniques. [ABSTRACT FROM AUTHOR]