Dollar Spot Research Articles

Mowing Frequency and Plant Growth Regulator Effects on Dollar Spot Severity and on Duration of Dollar Spot Control by Fungicides.

Management of dollar spot (incited by Sclerotinia homoeocarpa) on golf course fairways is increasingly challenging. The objectives of this study were to determine the influence of mowing frequency and plant growth regulators (PGRs) on dollar spot severity and on the residual efficacy of fungicides for control of dollar spot. Two 4-month-long studies were conducted on 'Putter' creeping bentgrass (Agrostis stolonifera) maintained as a fairway at the University of Connecticut. Treatments were arranged in a three-by-three-by-five factorial that assessed the influence of mowing frequency (2, 4, or 6 days week-1) and PGRs (paclobutrazol, trinexapac-ethyl, or none) on dollar spot control by five fungicide treatments (boscalid, chlorothalonil, iprodione, propiconazole, or none). Turf was mowed in the afternoon hours to minimize the confounding effect of mowing frequency on leaf wetness duration. Treatments were initiated in the late spring of 2007 and 2008, and each fungicide treatment was reapplied only when dollar spot exceeded a threshold of five infection centers plot-1. In the absence of fungicides, dollar spot severity was reduced by 63 to 90% in plots treated with paclobutrazol and by 13 to 55% in plots treated with trinexapac-ethyl. Dollar spot severity was 23 to 50% lower in plots mown 2 days week-1 compared with those mown 6 days week-1. In cases where a significant interaction was observed between mowing frequency and PGRs, dollar spot was reduced on most rating dates in plots treated with trinexapacethyl that were mown 2 days week-1 compared with those mown 6 days week-1. Survival analysis of days until threshold was met revealed that duration of control of fungicides in plots receiving paclobutrazol were 28 to 84% longer compared with plots not receiving PGR. Duration of control by fungicides was generally similar between plots treated with trinexapac-ethyl and no PGR. In general, mowing frequency did not influence duration of control. Results from this study indicate that paclobutrazol could be used to increase the treatment interval of fungicides and that mowing frequency in the absence of dew is likely to have little influence on fungicide residual efficacy. When used without fungicides, PGRs and less frequent mowing may reduce dollar spot in situations where fungicide use is limited.

Effects of Dew Removal and Mowing Frequency on Fungicide Performance for Dollar Spot Control.

Dollar spot (Sclerotinia homoeocarpa) is a severe disease problem on creeping bentgrass (Agrostis stolonifera) fairways. The objective of this study was to evaluate the effects of dew removal and mowing frequency on fungicide performance for dollar spot control. In 2009 and 2010, an experiment involving daily dew removal or no dew removal, mowing frequency (2, 4, and 6 days week-1), and fungicides (chlorothalonil, propiconazole, and iprodione) was conducted on creeping bentgrass maintained as a fairway. Daily dew removal resulted in fewer dollar spot infection centers (IC) compared with not removing dew during late summer 2009 and 2010 for all mowing-frequency and fungicide treatments. As mowing frequency increased from 2 to 6 days week-1, dollar spot IC decreased when averaged across all fungicide treatments. For all fungicides, daily dew removal increased the number of days needed to reach a 15-IC plot-1 point of reference when compared with fungicide treatments in which dew was not removed. The number of days required to reach 15 IC varied with fungicide, mowing frequency, and year the test was conducted. Results demonstrate that dollar spot control with fungicides can be extended when daily dew removal is employed and, in some cases, when mowing frequency is increased on dew-covered turf. Benefits of dew-removal practices on dollar spot and fungicide performance can vary with weather conditions, fungicide, threshold level, and possibly other factors.

Expression of a Novel Antimicrobial Peptide Penaeidin4-1 in Creeping Bentgrass (Agrostis stolonifera L.) Enhances Plant Fungal Disease Resistance

BackgroundTurfgrass species are agriculturally and economically important perennial crops. Turfgrass species are highly susceptible to a wide range of fungal pathogens. Dollar spot and brown patch, two important diseases caused by fungal pathogens Sclerotinia homoecarpa and Rhizoctonia solani, respectively, are among the most severe turfgrass diseases. Currently, turf fungal disease control mainly relies on fungicide treatments, which raises many concerns for human health and the environment. Antimicrobial peptides found in various organisms play an important role in innate immune response.Methodology/Principal FindingsThe antimicrobial peptide - Penaeidin4-1 (Pen4-1) from the shrimp, Litopenaeus setiferus has been reported to possess in vitro antifungal and antibacterial activities against various economically important fungal and bacterial pathogens. In this study, we have studied the feasibility of using this novel peptide for engineering enhanced disease resistance into creeping bentgrass plants (Agrostis stolonifera L., cv. Penn A-4). Two DNA constructs were prepared containing either the coding sequence of a single peptide, Pen4-1 or the DNA sequence coding for the transit signal peptide of the secreted tobacco AP24 protein translationally fused to the Pen4-1 coding sequence. A maize ubiquitin promoter was used in both constructs to drive gene expression. Transgenic turfgrass plants containing different DNA constructs were generated by Agrobacterium-mediated transformation and analyzed for transgene insertion and expression. In replicated in vitro and in vivo experiments under controlled environments, transgenic plants exhibited significantly enhanced resistance to dollar spot and brown patch, the two major fungal diseases in turfgrass. The targeting of Pen4-1 to endoplasmic reticulum by the transit peptide of AP24 protein did not significantly impact disease resistance in transgenic plants.Conclusion/SignificanceOur results demonstrate the effectiveness of Pen4-1 in a perennial species against fungal pathogens and suggest a potential strategy for engineering broad-spectrum fungal disease resistance in crop species.

Chromosomal regions associated with dollar spot resistance in colonial bentgrass

With 1 figure and 4 tables Abstract Interspecific hybridization between colonial bentgrass and creeping bentgrasses may be a useful approach for introducing resistance to Sclerotinia homoeocarpa, the causal agent of dollar spot disease, into creeping bentgrass. An interspecific backcross population of 271 genotypes was evaluated for dollar spot in a 2-year field study, and 11% of the genotypes were resistant to dollar spot. In the subset of the backcross population used for genetic linkage mapping, some resistant plants were identified, but no quantitative trait locus (QTL) was detected. A model of qualitative 3-gene recessive epistasis for dollar spot resistance in colonial bentgrass was proposed, and the limitations of QTL analysis to detect genomic regions conferring multigenic qualitative traits were examined. In the simulations, monogenic traits and 2-gene recessive epistatic traits were readily detectable by QTL analysis, whereas for 3-gene recessive epistasis, a QTL was not detectable. As an alternative to QTL analysis, screening of resistant plants from the backcross population for genomic regions held in common suggests that linkage groups 2A1 and 3A1 are possibly genomic locations of dollar spot resistance in colonial bentgrass.

Resistance to Rhizoctonia solani AG‐2‐2 (IIIB) in creeping bentgrass plants transformed with pepper esterase gene PepEST

A pepper esterase (PepEST) gene was introduced into creeping bentgrass (Agrostis stolonifera) by Agrobacterium‐mediated transformation. Purified recombinant PepEST proteins were sufficient to inhibit the growth of the fungal pathogens Rhizoctonia solani AG2‐2 (IIIB) (causing brown patch) and Sclerotinia homoeocarpa (dollar spot), but not the oomycete responsible for pythium blight, Pythium aphanidermatum. PepEST proteins were most effective against R. solani. After genetic transformation of creeping bentgrass with PepEST, the genomic integration of transgenes bar and PepEST was confirmed by Southern blot analysis, and their expression was also validated by northern blot and western blot analyses. Disease severity on R. solani‐inoculated leaves of transgenic plants was <10% compared to ca. 50% in non‐transgenic plants. Microscopic observation of infected leaves indicated that PepEST inhibited the growth of hyphae upon fungal infection.

First report of dollar spot of Agrostis stolonifera, Poa pratensis, Festuca arundinacea and Zoysia japonica caused by Sclerotinia homoeocarpa in China

Sclerotinia homoeocarpa causes dollar spot disease on many warm and cool season grasses. In Asia, this disease has only been formally reported in Japan (Hsiang & Mahuku, 1999) and south China (Lv et al., 2010). In China, the first anecdotal reports of dollar spot disease on turf were from the late 1990s, mainly in south China. For the past few years, this disease has been observed on cool season turfgrasses in north China with increasing severity. Outbreaks at golf courses in Beijing were observed in 2008, 2009 and 2010, where disease was first seen in early spring and developed from late spring until temperatures exceeded 32°C in early summer. When temperatures dropped below this in late summer, the disease flared up again until mid-autumn. Maximum disease development usually occurred on turf deficient in nitrogen and water, especially with warm days and cool nights with heavy dew.Characteristic hourglass foliar lesions were at first chlorotic, and then appeared water-soaked and finally bleached, with typical reddish-brown borders. Small patches appeared on turfgrasses, with a typical incidence of patches of 1-5/m2 and up to 50/m2 under high disease levels. In late May 2009, disease samples were collected from several golf courses in Beijing, and fungal isolates obtained from creeping bentgrass (Agrostis stolonifera), Kentucky bluegrass (Poa pratensis), tall fescue (Festuca arundinacea) and zoysia grass (Zoysia japonica). On potato dextrose agar (PDA) medium, white fluffy mycelia covered the whole petri dish three days after incubation, and formed brown columnar structures in the centres by seven days. Cultures more than 14 days old became cinnamon coloured and formed dark brown or black substratal stroma. Four-week-old seedlings of A. stolonifera cv. T-1, P. pratensis cv. Nu-Glade, F. arundinacea cv. Arid 3 and Z. japonica cv. Lanyin No. 3 were inoculated with 5-mm-diameter mycelial plugs of respective isolates of the fungus from five-day-old PDA cultures, by placing plugs onto the leaves and incubating under humid conditions. White aerial hyphae and leaf lesions were observed within seven days after inoculation on all four species of turfgrass, but no disease was seen with sterile agar plugs as inoculum. The fungus was re-isolated from lesions to satisfy Koch's postulates. DNA from one isolate per host species was amplified with internal transcribed spacer (ITS) primers and sequenced to yield 610 bp fragments (GenBank Accession Nos. GQ924923-GQ924926). Sequences were analysed by BLAST against GenBank, and showed over 99% identity with ITS regions of sequences identified as S. homoeocarpa. To the best of our knowledge, this is the first formal report of dollar spot disease on creeping bentgrass, Kentucky bluegrass, tall fescue or zoysia grass in China.

In vitro Assessment of Sclerotinia homoeocarpa Resistance to Fungicides and Plant Growth Regulators.

Dollar spot (caused by Sclerotinia homoeocarpa) is the most economically important turfgrass disease in North America. This disease is primarily controlled by fungicide applications on golf courses; however, fungicide resistance has been confirmed in three of the four systemic fungicide classes commonly used to control dollar spot. The main objective of this study was to evaluate S. homoeocarpa sensitivity to multiple chemical classes and cross-resistance among active ingredients within the same class; in particular, the association between the fungistatic effect of demethylation inhibitors (DMIs) and plant growth regulators (PGRs). Fifty-eight isolates were selected arbitrarily from four locations in the United States and assayed for in vitro sensitivity to six DMI, two dicarboximide, one carboximide, and one benzimidazole fungicide as well as three type II PGRs. A series of concentrations for each active ingredient was used to determine the mean 50% effective concentration (EC50) values and correlation coefficients were calculated for all active ingredients. The EC50 values of all active ingredients from the DMI class were highly correlated (P < 0.0001) to each other as well as to the one dicarboximide (iprodione) and two PGRs (flurprimidol and paclobutrazol). Isolates resistant to thiophanatemethyl had significantly higher EC50 values than sensitive isolates for all active ingredients assayed except for boscalid. Findings showed that multiple and cross-resistance has developed in S. homoeocarpa and that the two PGRs have a fungistatic effect on this pathogen similar to that of DMI fungicides. The high correlation of in vitro sensitivities among PGRs and DMI fungicides further suggests that PGRs may contribute to the selection of DMI-resistant isolates or facilitate decreased sensitivity to DMI fungicides in the field.

Registration of Turf‐Type Kentucky Bluegrass Cultivars ‘Awesome’, ‘Blue Velvet’, ‘Courtyard’, ‘Ginney’, and ‘Perfection’

Kentucky bluegrass (Poa pratensis L.) is typically grown in multiple‐cultivar blends for golf‐course, sports‐field, lawn, and landscape surfaces. This article describes the breeding and development of five cultivars, all sharing the common trait of tolerance to low mowing heights. ‘Awesome’ (Reg. No. CV‐96, PI 632299), ‘Blue Velvet’ (Reg. No. CV‐98, PI 635049), ‘Courtyard’ (Reg. No. CV‐97, PI 635048), ‘Ginney’(Reg. No. CV‐99, PI 634980), and ‘Perfection’ (Reg. No. CV‐95, PI 632298) are seed‐propagated, single‐clone, apomictic cultivars with minor, but measurable, differences in morphology. Awesome, Blue Velvet, Courtyard, and Perfection were developed from a hybrid cross between ‘Limousine’ and ‘Midnight’ Kentucky bluegrass. Ginney was developed from a hybrid cross between ‘Julia’ and Limousine. All five cultivars are classified as late in reproductive maturity. They are resistant to dollar spot (caused by Sclerotinia homoeocarpa F.T. Bennett), warm‐weather brown patch (caused by Rhizoctonia solani Kühn), and summer patch (caused by Magnaporthe poae Landschoot &amp; Jackson). Awesome, Blue Velvet, Courtyard, Ginney, and Perfection are recommended for golf‐course tees, fairways, and roughs and for lawns, parks, and sports turf, in full sun or partial shade, and in areas where Kentucky bluegrass is well adapted for turf. They are compatible in blends and mixtures with other cool‐season turfgrasses at mowing heights as low as 13 mm.

Gene Action of Dollar Spot Resistance in Creeping Bentgrass

The dollar spot disease, incited by Sclerotinia homoeocarpa F.T. Bennet, is one of the most important diseases of creeping bentgrass (Agrostis stolonifera L.) on golf courses. An understanding of the inheritance of dollar spot resistance could enhance genetic improvement efforts in creeping bentgrass. The objectives of this study were to evaluate the response of two creeping bentgrass crosses to two different isolates of S. homoeocarpa, determine gene action and identify number of loci involved in resistance to individual fungal isolates. Parental clones, pseudo F 2 , pseudo F 3 , BC 1 and BC 2 progenies from two crosses were established in a field trial in a randomized complete block split-plot design in the fall of 2002. Progeny of each generation (subplots) were inoculated with each of two isolates of S. homoeocarpa (main plots) applied at a rate of 0.25 g/m 2 of prepared inoculum and evaluated for dollar spot disease. Minimum loci calculations averaged 1.0-2.6. Midparent heterosis calculations were not significant. Backcross population means were closest to the recurrent parent. Generation mean analysis supports a simple additive-dominance model for both crosses and both isolates, although there was also some evidence of epistatic gene action depending on the cross and the isolate. These results confirm previous research that dollar spot disease is quantitatively inherited and indicate that there may be a few genes interacting in a mainly additive fashion to confer dollar spot disease resistance in creeping bentgrass.

The influence of Ophiostoma mitovirus-3a (OMV3a) on the respiration and growth of the dollar spot pathogen, Sclerotinia homoeocarpa (Bennett)

Sclerotinia homoeocarpa is the causal agent of dollar spot disease of turfgrass. Although both asymptomatic and hypovirulent isolates of S. homoeocarpa contain the mitochondrial virus Ophiostoma novo-ulmi mitovirus 3a (OMV3a), only asymptomatic isolates display growth rates and virulence levels comparable to that of virus-free isolates. In this study, the respiration and growth of asymptomatic, hypovirulent and virulent isolates of S. homoeocarpa were characterized using antimycin A (AA) as a complex III inhibitor, and salicylhydroxamic acid (SHAM) as an alternative oxidase inhibitor. Results of this study indicate that alternative oxidase contributes substantially to respiration by hypovirulent isolates. All S. homoeocarpa isolates appear to utilize the alternative pathway to some extent; however, hypovirulent isolates demonstrated a substantial increase in AOX transcription relative to asymptomatic and virulent isolates. These results demonstrate that OMV3a infection interferes with the normal function of mitochondria in S. homoeocarpa in hypovirulent isolates.

Trinexapac-Ethyl Influences Bispyribac-Sodium Absorption and Efficacy for Annual Bluegrass (Poa annua) Control in Creeping Bentgrass (Agrostis stolonifera)

Bispyribac-sodium selectively controls annual bluegrass in cool-season turf but efficacy may be influenced by management practices, such as plant growth regulator use. Experiments were conducted in New Jersey to investigate efficacy and absorption of bispyribac-sodium applied with trinexapac-ethyl for annual bluegrass control and turfgrass tolerance. In laboratory experiments with annual bluegrass, creeping bentgrass, and perennial ryegrass, tank-mixing trinexapac-ethyl with14C-bispyribac-sodium increased presumed foliar absorption of14C-bispyribac-sodium compared with nontrinexapac-ethyl treated; absorption increased with trinexapac-ethyl rate. Differences in14C-bispyribac-sodium absorption were not detected among emulsifiable concentration, microencapsulated concentration, and wettable powder trinexapac-ethyl formulations. In field experiments, sequential bispyribac-sodium applications controlled annual bluegrass 93%, but trinexapac-ethyl did not affect efficacy. Tank-mixing all trinexapac-ethyl formulations with bispyribac-sodium provided similar annual bluegrass control and creeping bentgrass quality compared with bispyribac-sodium alone. Applications of bispyribac-sodium reduced dollar spot cover in both years, whereas trinexapac-ethyl reduced dollar spot cover only in 2005.

Induced systemic resistance against three foliar diseases of Agrostis stolonifera by (2R,3R)‐butanediol or an isoparaffin mixture

Induced systemic resistance (ISR) is a type of plant defence mechanism typically activated by non‐pathogenic root‐associated micro‐organisms and systemic priming of gene expression in response to subsequent pathogen challenge. ISR was found to be activated by PC1, a mixture of food‐grade synthetic isoparaffins and (2R,3R)‐butanediol, a volatile organic compound produced by bacteria. In controlled environment tests, application of PC1 or (2R,3R)‐butanediol to the soil reduced the diseased leaf area of Agrostis stolonifera by 20–40% for the fungal pathogens, Microdochium nivale, Rhizoctonia solani or Sclerotinia homoeocarpa compared to the water control. In A. stolonifera, expression of the jasmonate synthesis‐related genes, AsAOS1, encoding an allene oxide synthase, and AsOPR4, encoding a 12‐oxo‐phytodienoic acid reductase, and expression of a pathogenesis‐related protein gene, AsGns5, encoding an acidic β‐1,3‐glucanase, were primed for increased expression by PC1 or (2R,3R)‐butanediol when M. nivale was inoculated 7 days later. However, the compounds differed in their ability to induce expression prior to pathogen challenge. PC1 induced AsAOS1 expression upon treatment, whereas (2R,3R)‐butanediol induced expression of AsOPR4 and AsGns5 upon treatment. These results indicate that both (2R,3R)‐butanediol and PC1 can produce ISR in A. stolonifera but may do so through different mechanisms.

Long Memory and Fractional Integration in High Frequency Financial Time Series

This paper analyses the long-memory properties of high frequency financial time series. It focuses on temporal aggregation and the influence that this might have on the degree of dependence of the series. Fractional integration or I(d) models are estimated with a variety of specifications for the error term. In brief, we find evidence that a lower degree of integration is associated with lower data frequencies. In particular, when the data are collected every 10 minutes there are several cases with values of d strictly smaller than 1, implying mean-reverting behaviour. This holds for all four series examined, namely Open, High, Low and Last observations for the British pound/US dollar spot exchange rate.

市販の微生物資材を利用したダラースボット病の生物防除 (1) , 防除効果の室外, 圃場検定

市販の微生物資材を利用したダラースボット病の生物防除 (1) , 防除効果の室外, 圃場検定

市販の微生物資材を利用したダラースボット病の生物防除 (2) .資材添加培地上の病原菌の生育

市販の微生物資材を利用したダラースボット病の生物防除 (2) .資材添加培地上の病原菌の生育

Genetic Characterization and Dollar Spot Fungus Susceptibility in Accessions of Festuca rubra from Northern Spain

The objective of the present study was to characterize the diversity of 15 Festuca rubra accessions collected from northern Spain on the basis of amplified fragment length polymorphism (AFLP) and flow cytometry variation. Additionally, all accessions along with the cultivar Wilma (Festuca nigrescens ssp. nigrescens) were evaluated for susceptibility to one isolate of dollar spot fungus (Sclerotinia homoeocarpa F.T. Bennett) collected in Asturias. Five AFLP primer combinations of EcoRI and MseI produced 980 bands; 82.3% were polymorphic and used for analysis. The best combination of primers was EcoRI-AGC+MseI-CAG, because these displayed the highest degree of polymorphism. Jaccard's similarity coefficients between accessions varied from 0.30 to 0.63 and revealed low genetic similarity. Both the unweighted pair group method with arithmetic mean dendrogram and principal coordinate analysis distinguished two groups of accessions. Genetic variability in these accessions was not related to the geographic origin or to the agronomic data. Three accessions exhibited moderate resistance to dollar spot disease and may be valuable parent material for introducing this resistance in other susceptible cultivars.

Simulated Rainfall and Mowing Impact Fungicide Performance When Targeting Dollar Spot in Creeping Bentgrass.

In this 2-year field study, four chemically diverse fungicides (i.e., chlorothalonil, boscalid, iprodione, and propiconazole) were evaluated for their ability to control dollar spot (Sclerotinia homoeocarpa) in creeping bentgrass (Agrostis stolonifera) as affected by simulated rain and mowing timing. Simulated rain (25 to 32 mm) was imposed about 30 min after fungicide application and was compared to rain-free plots. One set of plots was mowed in the morning when the canopy was wet with dew and compared to plots that were mowed when the canopy was dry in the afternoon. The percent reduction in dollar spot control associated with simulated-rain versus rain-free treatments in 2007 and 2008, respectively, was as follows: chlorothalonil 67 and 83%; propiconazole 42 and 79%; boscalid 48 and 70%; and iprodione 33 and 66%. When disease pressure was low, all fungicides subjected to simulated rain provided effective dollar spot control for 7 or more days following the initial application in each year. Across all fungicide-treated plots over 2 years, the average percent reduction in dollar spot associated with morning mowing ranged from 54 to 65%. The reduction in dollar spot severity in morning-mowed plots improved the performance of all fungicides.

Moss Control on Creeping Bentgrass Greens with Standard and Alternative Approaches

Moss is common on creeping bentgrass (Agrostis stolonifera L.) putting greens, and more control options are needed. Spot treatment of sodium bicarbonate (44.2 g·L−1) was compared with broadcast sprays of carfentrazone-ethyl (50.5 or 101 g a.i./ha), chlorothalonil (8.2 or 12.8 kg a.i./ha) and a tank mixture of chlorothalonil, mancozeb, and thiram (8.2, 9.8, and 11.5 kg a.i./ha) in 2006 in Lemont, IL. Sodium bicarbonate suppressed moss growth equally as the conventional products. These results led to further experiments in 2008 in which moss suppression was evaluated within standard and alternative putting green management regimes in Manhattan, KS, and Lemont, IL. The standard approach included spring and fall applications of carfentrazone-ethyl (101 g a.i./ha) for moss control, biweekly applications of urea (46N–0P–0K) at 15 kg N/ha, and applications of chlorothalonil (8.2 kg a.i./ha) on a 14-day interval. Conversely, the alternative approach included spring and fall spot treatments of sodium bicarbonate (44.2 g·L−1) for moss control, biweekly applications of a natural organic fertilizer (8N–1P–3K) to provide nitrogen at 15 kg N/ha, and applications of chlorothalonil (8.2 kg a.i./ha) only when dollar spot reached a predetermined threshold level. Standard and alternative regimes were compared at both 3.2- and 4.0-mm mowing heights; synthetic and organic fertilizers applied alone without pest control approaches were included as controls. In Kansas and Illinois, moss coverage using the alternative management regime was not significantly different from that on greens managed using the standard regime. In Kansas, moss severity at a 3.2 mm was 1.6-fold higher than at the 4.0-mm height. In Illinois, sodium bicarbonate suppressed moss equivalently to the carfentrazone-ethyl treatment, and in the fertilizer-only controls, mowing at 3.2 versus 4.0 mm led to more moss coverage. These studies demonstrate that moss can be effectively suppressed on greens using spot applications of sodium bicarbonate and reduced moss encroachment is possible with higher mowing heights.

First Report of Dollar Spot of Seashore Paspalum (Paspalum vaginatum) Caused by Sclerotinia homoeocarpa in South China.

Seashore paspalum (Paspalum vaginatum Swartz), a warm-season perennial grass, is native to tropical and subtropical regions of North and South America (1). Its fine texture and tolerance to low mowing and hypersaline environments make it a commercially promising turfgrass species for coastal regions of south China. In late March 2009, disease symptoms were observed from two golf course fairways in Shenzhen and Foshan, Guangdong Province, China. Small, round patches from 25 to 75 mm in diameter were found to be consisting of bleached, straw color leaf lesions bounded by reddish brown margins. Similar patches had previously been observed on seashore paspalum since 1997 in Guangdong Province, but this turf species has been grown in southern China only since the early 1990s. These symptoms were observed when daytime temperatures were above 25°C and with heavy dew formation at night. Greatest severity was seen in the spring and fall. Several contact and systemic fungicides were applied after first symptoms were observed and they were usually successful in suppressing disease. To confirm the disease as dollar spot, isolates from Shenzhen and Foshan were obtained by plating diseased leaf blades of P. vaginatum (cv. Salam) on potato dextrose agar media. Isolates produced white, fluffy, aerial mycelium, columnar when mature, and usually with a cinnamon base and dark brown or black substratal stroma on and in the agar. One representative isolate from each location was chosen for pathogenicity testing. Six-week-old P. vaginatum (cv. Salam) grown from seed in pots was inoculated, with 5-mm-diameter agar plugs with hyphae from 5-day-old cultures, by direct placement onto leaves and with three replicate pots per isolate. Plants treated with sterile agar plugs served as controls. Inoculated turf was incubated at 25°C with 12-h light/dark conditions. A plastic film was also placed over the pots to retain moisture. Chlorotic leaf lesions started to develop 4 days after inoculation and became a bleached straw color. The same fluffy, white fungus was reisolated from lesions, while no disease was observed on controls, thus completing Koch's postulates. The internal transcribed spacer (ITS) region of the ribosomal DNA was amplified from DNA extracted from two isolates using primers ITS5 and ITS4 (2), and the 610-bp sequences showed 98% similarity with Sclerotinia homoeocarpa F.T. Bennett in GenBank and have been deposited as Accessions GQ386985 and GU002301. Dollar spot on P. vaginatum has been commonly observed in the United States (1). To our knowledge, this is the first confirmed report of dollar spot on P. vaginatum in China or from any host plant in China.

Agromorphological characterization and dollar spot fungus susceptibility in accessions of common bent (Agrostis capillaris L.) collected in Northern Spain

Fourteen Agrostis capillaris accessions collected in northern Spain were characterized in a trial with a lowfertilization regime, carried out in two successive years (2004 and 2005). The commercial cultivar "Golfin" was included in the study as a control. All accessions and the commercial cultivar were evaluated for 11 agromorphological characteristics and susceptibility to dollar spot disease, caused by Sclerotinia homoeocarpa F.T. Bennet. The data obtained were reduced to five principal components that cumulatively explained 85.4% of the total variance. Cluster analysis was useful in identifying four groups of accessions that described 50% of the phenotypic variation among accessions. Cluster 1 consisted of four accessions with the highest resistance to dollar spot, dark green colour, late heading date and high autumn turf quality. Cluster 2 included the two earliest heading accessions, dark green colour, intermediate tolerance to dollar spot and low autumn turf quality. Cluster 3 comprised six accessions with the latest heading date, dark green colour and low tolerance to dollar spot. Cluster 4 consisted of two accessions and the "Golfin" cultivar, with lightest green colour, low autumn turf quality and the poorest tolerance to dollar spot. The results of this study suggest the potential value of some of these common bent accessions collected in northern Spain for turf and forage improvement.