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Rhizoctonia large patch (Rhizoctonia solani AG2-2 LP) significantly reduces turfgrass quality, aesthetics, and playability. Synthetic fungicides are commonly used for managing this disease, but they present high costs, potential for fungicide resistance, and environmental concerns. We conducted in vitro assays to test the effectiveness of three biofungicides, seven synthetic fungicides, and ten combinations against R. solani. We then assessed seven spray programs that included Bacillus subtilis QST713 and propiconazole, either alone or tank-mixed, on zoysiagrass 'El Toro' in a growth chamber and in field trials. Biofungicide B. subtilis QST713 reduced pathogen growth by up to 100% in vitro. B. subtilis QST713 alone or combined with synthetic fungicides and/or in rotation was as effective as the standalone synthetic fungicide, reducing disease severity and AUDPC by 81 and 77% (growth chamber) and by 71 and 52% (field), respectively, while maintaining acceptable turfgrass quality. Additionally, we screened zoysiagrass genotypes and advanced breeding lines against three R. solani isolates in growth chamber studies. Five genotypes and two breeding lines demonstrated resistance to Rhizoctonia large patch across isolates, highlighting their potential for developing disease-resistant cultivars. Our findings suggest that integrating biofungicides, resistant cultivars with chemical controls offer sustainable and effective strategies for managing Rhizoctonia large patch [ABSTRACT FROM AUTHOR]

Dollar spot caused by Clarireedia spp. (formerly Sclerotinia homoeocarpa) is an economically destructive fungal disease of turfgrass that can significantly compromise turf quality, playability, and aesthetic value. Fungicides are frequently used to manage the disease but are costly and potentially unfavorable to the environment. Repeated use of some active ingredients has resulted in reduced efficacy on C. jacksonii causing dollar spot in cool-season turfgrasses in the US. Experiments were conducted to study fungicide sensitivity of Clarireedia spp. as well as to develop alternatives to fungicides against dollar spot on warm-season turfgrass in Georgia. First, 79 isolates of Clarireedia spp. collected across the state were tested on fungicide-amended agar plates for their sensitivity to thiophanate-methyl (benzimidazole) and propiconazole (dimethyl inhibitor). Seventy-seven isolates (97.5%) were sensitive (0.001 to 0.654 mg/mL) and two isolates (2.5%) were found resistant (>1000 mg/mL) to thiophanate-methyl. However, in the case of propiconazole, 27 isolates (34.2%) were sensitive (0.005 to 0.098 mg/mL) while 52 isolates (65.8%) were resistant (0.101 to 3.820 mg/mL). Next, the efficacy of three bio- and six synthetic fungicides and ten different combinations were tested in vitro against C. monteithiana. Seven bio- and synthetic fungicide spray programs comprising Bacillus subtilis QST713 and propiconazole were further tested, either alone or in a tank mix in a reduced rate, on dollar spot infected bermudagrass 'TifTuf' in growth chamber and field environments. These fungicides were selected as they were found to significantly reduce pathogen growth up to 100% on in vitro assays. The most effective spray program in growth chamber assays was 100% B. subtilis QST713 in rotation with 75% B. subtilis QST713 + 25% propiconazole tank mix applied every 14 days. However, the stand-alone application of the biofungicide B. subtilis QST713 every seven days was an effective alternative and equally efficacious as propiconazole, suppressing dollar spot severity and AUDPC up to 75%, while resulting in acceptable turf quality (>7.0) in field experiments. Our study suggests that increased resistance of Clarireedia spp. to benzimidazoles and dimethyl inhibitors warrants continuous surveillance and that biofungicides hold promise to complement synthetic fungicides in an efficacious and environmentally friendly disease management program. [ABSTRACT FROM AUTHOR]

Middle East-Asia Minor 1 (MEAM1) and Mediterranean (MED) are two of the most invasive members of the sweetpotato whitefly, Bemisia tabaci, cryptic species complexes and are efficient vectors of begomoviruses. Bemisia tabaci MEAM1 is the predominant vector of begomoviruses in open-field vegetable crops in the southeastern United States. However, recently B. tabaci MED also has been detected in the landscape outside of greenhouses in Florida and Georgia. This study compared the transmission efficiency of one Old-World (OW) and two New-World (NW) begomoviruses prevalent in the southeastern United States, viz., tomato yellow leaf curl virus (TYLCV), cucurbit leaf crumple virus (CuLCrV), and sida golden mosaic virus (SiGMV) between B. tabaci MEAM1 and B. tabaci MED. Bemisia tabaci MEAM1 efficiently transmitted TYLCV, CuLCrV, or SiGMV, whereas B. tabaci MED only transmitted TYLCV. Percent acquisition and retention of OW TYLCV following a 72 h acquisition access period was significantly higher for B. tabaci MED than B. tabaci MEAM1. In contrast, B. tabaci MEAM1 acquired and retained significantly more NW bipartite begomoviruses, CuLCrV or SiGMV, than B. tabaci MED. Quantitative analysis (qPCR) of virus DNA in whitefly internal tissues revealed reduced accumulation of CuLCrV or SiGMV in B. tabaci MED than in B. tabaci MEAM1. Fluorescent in situ hybridization (FISH) showed localization of CuLCrV or SiGMV in the midgut of B. tabaci MED and B. tabaci MEAM1. However, localization of CuLCrV or SiGMV was only observed in the primary salivary glands of B. tabaci MEAM1 and not B. tabaci MED. TYLCV localization was observed in all internal tissues of B. tabaci MEAM1 and B. tabaci MED. Overall, results demonstrate that both B. tabaci MEAM1 and B. tabaci MED are efficient vectors of OW TYLCV. However, for the NW begomoviruses, CuLCrV and SiGMV, B. tabaci MEAM1 seems to a better vector. [ABSTRACT FROM AUTHOR]

The physical and chemical mechanisms that mediate adhesion of Rhodosporidium toruloides to polystyrene and barley leaves are investigated. To this end, cell surface charge and hydrophobicity and attachment to glass, barley and polystyrene are studied for wild-type Rhodosporidium toruloides and attachment-minus variants. Results show that localized, positive charge rather than hydrophobic interactions mediates the adhesion of Rhodosporidium toruloides to barley leaves.

Research was conducted to examine the adhesion of the basidiomycetous yeast Rhodosporidium toruloides to plant surfaces. Nonadherent fungal mutants were obtained after chemical mutagenesis with methane-sulfonic acid ethyl ester. Enzyme, lectin and chemical treatments revealed that the polar regions consisted of alkali-soluble materials. Results indicate that compounds localized at sites of bud development mediate the adhesion of R. toruloides to both barley leaf and polysterene surfaces.

The presence of rusts of daylily and geranium caused respectively by Puccinia hemerocallidis and P. pelargonii-zonalis can result in reduced value of these ornamental crops. Experiments were conducted to determine the effects of fluorescent light and sunlight on urediniospore germination, germ tube elongation, lesion development and sporulation of the two fungal pathogens on detached leaves and whole plants. Exposure of dry or hydrated urediniospores of P. hemerocallidis to cool white fluorescent light (600 µmol s-1 m-2) or to sunlight (950-1910 µmol s-1 m-2) for 2 h or 4 h significantly reduced germination and germ tube elongation on detached daylily leaves. Germination but not germ tube elongation of hydrated urediniospores of P. pelargonii-zonalis on detached geranium leaves was significantly reduced when exposed to fluorescent light for 2 h or 4 h. A 4 h exposure to either light source significantly reduced lesion development of P. hemerocallidis on detached daylily leaves with fewer lesions developing from hydrated compared to dry urediniospores. Sunlight exposures of 1 h and 2 h of hydrated and dry urediniospores respectively significantly reduced lesion development by either fungus on whole plants. Increasing exposure to fluorescent light negatively affected sporulation of P. hemerocallidis and P. pelargonii-zonalis. Complete suppression of sporulation was not observed for either fungus with up to a 24 h exposure to fluorescent light. Light exposure negatively affected disease development by P. hemerocallidis and P. pelargonii-zonalis. Exposure to high light intensities may affect spread of rust diseases on ornamental plants. [ABSTRACT FROM AUTHOR]

Xanthomonas transtucens contains a group of bacterial pathogens that are closely related and have been divided into several pathovars based on their host range. X. translucens pv. undulosa (Xtu) and X. translucens pv. translucens (Xtt) are two important pathovars that cause bacterial leaf streak disease on wheat and barley, respectively. In this study, DNA markers were developed to differentiate Xtu and Xtt and were then used to characterize a collection of X. translucens strains with diverse origins, followed by confirmation and characterization with pathogenicity tests and multilocus sequence analysis/typing (MLSA/MLST). We first developed cleaved amplified polymorphic sequence markers based on the singlenucleotide polymorphisms within acereal pathovar-specific DNA sequence. In addition, two Xtt-specific markers, designated Xtt-XopM and Xtt-SPl, were developed from comparative genomics among the sequenced Xtt/Xtu genomes. Using the developed markers, a collection of X. transhicens strains were successfully identified as Xtu or Xtt. Pathogenicity tests on wheat and barley plants and MLSA of four housekeeping genes validated the pathovar assignation of those strains. Furthermore, MLSA revealed distinct subclades within both Xtu and Xtt groups. Seven and three sequence types were identified from MLST for Xtu and Xtt strains. respectively. The establishment of efficient Xtuxtu differentiation methods and characterization of those strains will be useful in studying disease epidemiology and host-pathogen interactions and breeding programs when screening for sources of resistance for these two important bacterial pathogens. [ABSTRACT FROM AUTHOR]