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In late July of 2022, corn leaves with spots were observed in a field at North Carolina State University’s Vernon James Research and Extension Center (35.873294º N, 76.658599º W; Plymouth NC). The affected leaves contained small (two to three millimeters in diameter) tan-colored circular to oval lesions with reddish-brown margins and chlorotic haloes. The disease severity approached 50% on affected leaves. Leaf tissue from the margins of the lesions was excised and surface sterilized by soaking in 10 % bleach solution for two minutes followed by rinsing in distilled water. Next, leaf tissue was transferred to alkaline water agar amended with streptomycin (100 mgliter-1) and the plates were incubated at 27º C in dark. After one week, conidia were observed. Conidia were curved, light brown in color and contained three transverse septa. The size of the conidia (n= 30) ranged from 21-25 µm (average 24 µm) long by 7 to 10 µm wide (average 9 µm). These characteristics were typical of Curvularia lunata (Munkvold and White 2016). DNA from pure cultures was extracted, internal transcribed space region (ITS) was amplified using the primers ITS4 and ITS5 (White et al. 1990). Sequences were obtained and deposited into GenBank (accession no. OP998306). BLAST search indicated that the sequence was 100 % identical to C. lunata from Louisiana (MG 971305.1, Garcia- Aroca et al. 2018). Pathogenicity was confirmed on field corn cultivar ‘Yellow dent’ by inoculating two pots of two-week-old greenhouse-grown corn plants (6 plants per pot) by spraying conidial suspension with a concentration of 6 x 104 conidia /ml. The control plants (n= 6) were sprayed with distilled water and the plants were covered with a plastic bag for 24 hours. The plastic bags were removed and plants were moved to the greenhouse at 23º C. Four days after inoculation small round tan-colored lesions were observed and no symptoms on control plants. The experiment was repeated once and the pathogen was recovered from the symptomatic tissue. The morphology of the recovered isolate was similar to the original isolate. This is the first report of C. lunata causing leaf spot on corn in North Carolina. Although this disease has not been demonstrated to cause yield loss it has been detected more frequently in corn production areas of U.S. and should continue to be monitored going forward.

Botrytis spp. cause gray mold and are significant pathogens of pulse crops (dry pea, lentil, and chickpea). Seedling infection can result in plant stunting and death. In this study, 100 Botrytis isolates were recovered from pulse crop seed samples that were submitted to the Regional Pulse Crop Diagnostic Laboratory at Montana State University. Nine Botrytis spp. were found to be associated with pulse seeds in Montana based on a combination of cultural characteristics; the amplification of partial sequences of the G3PDH, HSP60, and RPB2 genes; and phylogenetic analysis. Botrytis cinerea (n = 54) was the predominant species, followed by B. euroamericana (n = 22) and B. prunorum (n = 11). There were a few isolates of B. mali and five novel Botrytis spp. that included one cryptic species. To determine the pathogenicity and aggressiveness of the isolates, dry pea cultivar Lifter, lentil cultivar Richlea, and chickpea cultivar Sierra, detached leaves were inoculated using mycelial plugs. Lesion diameter produced by Botrytis isolates on three hosts differed (P < 0.05). Aggressiveness of B. cinerea was high in all three hosts and varied among the tested isolates. Spore inoculations were conducted on greenhouse-grown dry pea, lentil and chickpea plants using one sporulating isolate each of B. cinerea, B. prunorum, and Botrytis sp. 1. Results indicated that these isolates were pathogenic on the tested hosts. This study illustrates that many species of Botrytis are associated with pulse crop seed in Montana and can be aggressive on multiple crops, which may have implications for disease management.

Powdery mildew caused by Podosphaera cerasi is a detrimental fungal disease for the sweet cherry industry. Epidemics in orchards are initialized by ascospores that are released from chasmothecia generated in the fall of the previous year, however, the initiation of epidemics in nurseries has not been explored. The current study aimed to evaluate the origin of disease epidemics in Washington State cherry tree nurseries and to evaluate the efficacy of different fungicide regimes to suppress chasmothecia numbers and ascospore viability. Greenhouse and lab assays in the present study showed that chasmothecia from the nursery are not contributing to powdery mildew epidemics and the disease is originating from an external source such as wind-blown conidia from neighboring orchards. Additionally, intensive synthetic fungicide regimes and late-season JMS Stylet-Oil applications were found to be viable options to inhibit chasmothecia formation. As chasmothecia with a nursery origin are not the initial inoculum, late season fungicide applications to limit chasmothcia formation should only be applied in an orchard setting. Orchard managers can limit epidemics by implementing late-season fungicide applications into their IPM plan that target chasmothecia. Future research should evaluate the dispersal of conidia throughout the cherry tree growing industry of Washington and their role in powdery mildew epidemics in nurseries. Moreover, the physiological and genetic differences between chasmothecia in the nursery and the orchard should be evaluated.

Root rot caused by Fusarium species is a major problem in the pulse growing regions of Montana. Fusarium isolates (n = 112) were obtained from seeds and roots of chickpea, dry pea, and lentil. Isolates were identified by comparing the sequences of the internal transcribed spacer region and the translation elongation factor 1-α in Fusarium-ID database. Fusarium avenaceum was the most abundant species (28%), followed by F. acuminatum (21%), F. poae (13%), F. oxysporum (8%), F. culmorum (6%), F. redolens (6%), F. sporotrichioides (6%), F. solani (4%), F. graminearum (2%), F. torulosum (2%), and F. tricinctum (0.9%). The aggressiveness of a subset of 50 isolates that represent various sources of isolation was tested on three pulse crops and two cereal crops. Nonparametric analysis of variance conducted on ranks of disease severity indicated that F. avenaceum and F. solani isolates were highly aggressive on pea and chickpea. In lentil, F. avenaceum and F. culmorum were highly aggressive. In barley, F. avenaceum, F. solani, F. culmorum, and F. graminearum were highly aggressive. In wheat, F. avenaceum, F. graminearum, and F. culmorum were highly aggressive. Two F. avenaceum isolates were highly aggressive across all the crops tested and found to be cross-pathogenic. One isolate of F. culmorum and an isolate of F. graminearum obtained from chickpea and lentil seed were highly aggressive on barley and wheat. The results indicate that multiple Fusarium spp. from seeds and roots can cause root rot on both pulse and cereal crops. Rotating these crops may still lead to an increase in inoculum levels, making crop rotation limited in efficacy as a disease management strategy.

Powdery mildew is a detrimental foliar disease of sweet cherry trees. The disease is predominantly managed by spraying synthetic fungicides throughout the growing season. The emergence of resistant...

Powdery mildew of Prunus spp. is a significant disease in most cherry growing regions of Washington, USA. Powdery mildews on Prunus virginiana and Pr. avium were previously assigned to Podosphaera clandestina s. lat. (= Po. oxyacanthae) or Po. prunicola. In this report, we confirm the presence of two distinct Podosphaera species on these hosts. Phylogenetic analyses of nuc rDNA sequences from the internal transcribed spacer region (ITS1-5.8S-ITS2 = ITS) and 28S subunit confirmed the presence of two distinct species. A morphological comparison with type material of Po. prunicola and additional collections demonstrated that the powdery mildew on Pr. virginiana (including var. demissa and var. melanocarpa) is in fact Po. prunicola. The powdery mildew on Pr. avium is genetically, morphologically, and biologically distinct from Po. prunicola and is described here as the new species Po. cerasi. Cross-inoculation experiments confirmed that these two species are host specific. Podosphaera prunicola was unable to colonize Pr. avium, whereas Po. cerasi was unable to colonize Pr. virginiana. Morphological reexamination of numerous specimens identified as Po. prunicola on a broad range of Prunus species suggests that Po. prunicola is probably confined to species in Prunus subgen.Padus (= Prunus subgen. Cerasus sect. Laurocerasus, including sect. Padus), with Pr. virginiana as the principal host. Podosphaera cerasi occurs on hosts in Prunus subgen. Cerasus, and our work confirms a newly described species of powdery mildew on Pr. avium. This work also includes the first documented and genetically proven European record of Po. prunicola on Pr. serotina and its widespread occurrence in the United States.

Podosphaera spiraeae is a common fungal pathogen for plants in the genus Spiraea. The pathogen is native to Japan but is most likely widespread throughout the temperate world where viable host plants occur. Identification of powdery mildew on Spiraea spp. can be difficult and its occurrence has not been well documented. Wind dispersal of asexual spores, known as conidia, spreads powdery mildew between viable host plants. The most likely long-distance pathway of invasion is through the nursery industry, which commonly trades Spiraea plants. P. spiraeae can be detrimental to nursery growers as it is unsightly, reduces photosynthesis and flower vigour and causes premature leaf drop. Primary control of the pathogenic fungus requires intricate integrated pest management regimes.

Pythium root rot and damping-off caused by Pythium spp. are important diseases of pulse crops. In a 2016 pathogen survey from dry pea growing fields in Montana, along with commonly known causal agents P. ultimum and P. irregulare, an isolate identified as P. sylvaticum (LPPY17) was isolated from the rhizosphere of a diseased pea plant collected from Valley County, MT. Root rots and damping-off caused by P. sylvaticum have not previously been reported for chickpea, pea, and lentil crops. The isolate LPPY17 was tested for fungicide resistance in vitro, and results indicated a reduced sensitivity to metalaxyl- and ethaboxam-containing fungicides. LPPY17 was also tested for pathogenicity on chickpea, pea, and lentil seedlings in the greenhouse, and the results from the study revealed LPPY17 is capable of causing both root rots and damping-off. Due to the potential pathogenicity and reduced fungicide sensitivity of this species, in the future it will be important to monitor for P. sylvaticum in pulse root rot surveys and diagnostics, because management options may be different from other common Pythium spp.

Powdery mildew of

Gray mold caused by Botrytis spp. is one of the most important diseases of chickpea. In August 2019, chickpea plants with gray mold symptoms were submitted to the Regional Pulse Crop Diagnostic Laboratory (RPCDL) at Montana State University (MSU). To identify the causal agent, leaves were surface sterilized and plated on potato dextrose agar (PDA). The fungus was off white color and did not sporulate on PDA; sclerotia were observed after 10 days of incubation. The pathogen was identified as Botrytis euroamericana by the amplification of part of the G3PDH, HSP60, and RPB2 genes and by phylogenetic analysis. Pathogenicity tests revealed that the isolate was able to cause lesions on chickpea, lentil, dry pea, and fava bean foliage.

Helianthus annuus is a perennial plant native to the USA. Commonly known as a sunflower, H. annuus is grown ornamentally as well as for its oil and seeds. It can grow up to 8 feet in height. In August 2017, Helianthus annus ‘Lemon Queen’ leaves showing signs of powdery mildew were collected from the Pierce County master garden located at WSU Puyallup Research and Extension Center (47.2258oN, 122.4347oW). Signs of the powdery mildew included dense patches of white to greyish mycelia on the leaf surfaces. The fungus formed superficial branched hyphae with septa. The foot cells were straight and were followed by one to three short cells bearing conidia. The conidiophores contained short chains of up to 5 conidia. The hyphal appressoria were nipple shaped. The conidia were hyaline and ellipsoidal. Eudoidium type of conidial germination with a short germ tube developed. The conidia (N=55) ranged from 29 to 39 μm long (average=36 μm) by 16 to 24 μm wide (average=18.61 μm). Chasmothecia showed myceloid appendage...

Spiraea japonica is a perennial ornamental plant that belongs to the family Rosaceae. It is grown as an ornamental plant throughout the USA. In the summer of 2017, Japanese Spiraea plants growing at Washington State University Puyallup Research and Extension Center (47.1882oN, 122.3290oW) showed signs of powdery mildew. Signs of powdery mildew include dense patches of white to greyish mycelia on leaf surfaces. The fungus formed superficial branched hyphae with septa. The foot cells of the conidiophore were straight followed by one to three short cells bearing conidia in short chains. The size of the foot cell ranged from 55 to 105 μm with an average of 93.76 μm (n=30). Appressorium was nipple shaped and the germ tubes of the conidia were terminal. Conidia were formed in chains of up to 5-7 hyaline, broad ellipsoidal spores which measured 25 × 15 (21 to 28 × 12 to 19) μm. Chasmothecia did not form during the time of observation (July- October of 2017). These features were consistent with the description of...

Background Enterobacter sp. YSU is resistant to several different heavy metal salts, including selenite. A previous study using M-9 minimal medium showed that when the selenite concentration was 100,000 times higher than the sulfate concentration, selenite entered Escherichia coli cells using two pathways: a specific and a non-specific pathway. In the specific pathway, selenite entered the cells through a yet to be characterized channel dedicated for selenite. In the non-specific pathway, selenite entered the cells through a sulfate permease channel. Addition of L-cystine, an L-cysteine dimer, appeared to indirectly decrease selenite import into the cell through the non-specific pathway. However, it did not affect the level of selenite transport into the cell through the specific pathway. Results Growth curves using M-9 minimal medium containing 40 mM selenite and 1 mM sulfate showed that Enterobacter sp. YSU grew when L-cysteine was present but died when it was absent. Differential protein expression analysis by two dimensional gel electrophoresis showed that CysK was present in cultures containing selenite and lacking L-cysteine but absent in cultures containing both selenite and L-cysteine. Additional RT-PCR studies demonstrated that transcripts for the sulfate permease genes, cysA, cysT and cysW, were down-regulated in the presence of L-cysteine. Conclusion L-cysteine appeared to confer selenite resistance upon Enterobacter sp. YSU by decreasing the level of selenite transport into the cell through the non-specific pathway.