Lindholmstephansen5414

Soybean seedlings are vulnerable to different oomycete pathogens. Seed treatments containing the two anti-oomycete (oomicide) chemicals, metalaxyl-M (mefenoxam), and ethaboxam are used for the protection against oomycete pathogens. This study aimed to evaluate the influence of these two oomicides on the isolation probability of oomycetes from soybean taproot or lateral root sections. Soybean plants were collected between the first and third trifoliate growth stages from five Midwest field locations in 2016 and four of the same fields in 2017. Tamoxifen cell line Oomycetes were isolated from taproot and lateral root. In 2016, 369 isolation attempts were completed resulting in 121 isolates from the taproot and 154 isolates from the lateral root. In 2017, 468 isolation attempts were completed, with 44 isolates from the taproot and 120 isolates from the lateral roots. In three of nine site-years, the probability of isolating an oomycete from a taproot or lateral root section was significantly different. Seed treatments containing a g ml-1 with a median of 0.03 μg ml-1. The mean EC50 of the five most abundant species to ethaboxam ranged from 0.35 to 0.97 μg ml-1 of ethaboxam and from 0.02 to 0.04 μg ml-1 of mefenoxam. No shift in sensitivity to mefenoxam or ethaboxam was observed due to soybean seed treatment or year relative to the non-treated seed controls. In summary, this study contributed to the understanding of the composition of oomycete populations from different soybean root tissues, locations, years, and seed treatments. Finally, the effectiveness of seed treatments containing mefenoxam or metalaxyl plus ethaboxam can be effective in reducing the probability of oomycete isolation from soybean roots.The complex etiology of cranberry fruit rot (CFR) (Oudemans et al., 1998) has made it difficult to precisely identify the fungi involved in CFR and their relative importance in North America. To remedy this situation, a multiplex PCR approach targeting the 12 most commonly reported fungi in CFR was recently developed (Conti et al., 2019). However, in surveys conducted in Eastern Canada, the molecular tool revealed the presence of an unknown fungus in more than 30% of the collected samples. Analyses were thus undertaken to identify this species. From 117 rotten fruit collected at harvest in 2017, 34 samples of the unknown fungus, all morphologically similar, were isolated but not detected using the molecular tool. Their ITS ribosomal regions were sequenced using universal primers (Vilgalys and Hester, 1990; White et al., 1990) and searched against the GenBank database using the Blastn tool (Altschul et al., 1990). The top match was obtained with Godronia cassandrae (accession number MH855281 (Vu et al., 2019),7). Rot symptoms appear as a discoloration from the firm, red and healthy cranberry fruit to a yellowish-orange softer fruit. Molecular characterization of the re-isolated fungus confirmed the presence of G. cassandrae. We report Godronia cassandrae for the first time as a major cause of CFR in Eastern Canada. Its prevalence in cranberry fields of Québec and Nova Scotia suggests that it supplants Physalospora as the main fungus involved in CFR in Eastern Canada.The effects of cover crops on the biology of the soybean cyst nematode (SCN), Heterodera glycines, are not well established. It is possible that cover crops may reduce SCN population densities by acting as trap crops. Cover crops with potential to serve as trap crops may stimulate hatching and/or attract hatched SCN juveniles and also may be penetrated by large numbers of nematodes that cannot feed. Experiments were conducted to determine if root exudates and soil leachates (RE+SL) from various cover crop plants affected SCN hatching and chemotaxis and if there were significant differences in SCN juvenile root penetration among different cover crop plant types. In fourteen-day-long hatching experiments, there was greater SCN hatching in crimson clover (Trifolium incarnatum) RE+SL than in RE+SL from all other cover crop treatments in the experiments. No other cover crop RE+SL significantly affected hatching. In chemotaxis experiments, SCN juveniles were attracted to RE+SL from annual ryegrass (Lolium multiflorum) and cereal rye (Secale cereal) after 24 hours. In greenhouse experiments, significantly more SCN juveniles penetrated the roots of single cultivars of crimson clover, mustard (Brassica juncea), and rapeseed (Brassica napus) than 11 other cover crop species/cultivars evaluated in the experiment over the course of 20 days. Few SCN juveniles penetrated the roots of annual ryegrass and cereal rye. The results suggest crimson clover, grown as a cover crop, has the most potential to act as a trap crop for SCN. Cover crop plants may affect SCN biology in ways other than the mechanisms investigated in these experiments.In September 2014, a high rate of bulb rot (5-15% depending on producer) was reported across all cultivars developing early in the storage season in the onion producing region of southwestern Idaho. Spanish yellow onion bulbs cv. Vaquero displaying tan to light brown necrotic rot were obtained. The bulb rot originated in the neck and spread to successive scales (Figure 1). In August 2015, onion cv. Redwing and Vaquero were observed to have wet necrotic lesions developing on leaves in the field (Figure 2). Margins of necrotic tissue, 1-2 cm3, were excised, surface sterilized, plated on water agar medium and incubated at 24°C. Hyphal growth was sub-cultured from eight strains (A- D in 2014; E-H in 2015) to fresh potato dextrose agar to obtain pure cultures. Cultures were characteristic of Fusarium species as described by Nelson et al. (1983) with the presence of microconidia formed on polyphialides with macroconidia present. Primers ITS4-A1 and ITS5 primers (White et al. 1990); EF-1 and EF-2 (O'Donnell et al. 1 storage in Idaho (Mohan et al. 1997). In addition, this is the first report of the fungus causing leaf infection in the field. These findings confirm F. proliferatum as the causal agent of the high incidence of bulb rot observed in 2014 and 2015. This bulb rot continues to occur in southwestern Idaho and since the pathogen can cause leaf infections growers are encouraged to be vigilant for both leaf lesions during the growing season and bulb rot in storage.Vicia sativa subsp. nigra, also known as narrow-leaved vetch, belongs to the family Fabaceae and is distributed in different countries.Vetch is one of the most important annual forage legumes in the world; it is used as hay, grain, silage, green manure, and livestock fodder. In Korea, this plant is often used as cattle feed. In early May of 2019 and 2020, a powdery mildew was observed on leaves of V. sativa subsp. nigra plants in a garden of Chonnam National University, Gwangju, Korea. The first symptom appeared on the upper surface of the leaves as a small white spot. Within two weeks, the white spots of powdery mildew spread and covered the entire leaf. Voucher specimens were deposited at the Environmental Microbiology Laboratory Herbarium, Chonnam National University, Gwangju, Korea, under the accession numbers CNUFC PWV1 and CNUFC PWV2. The hyphal appressoria of the fungus were nipple-shaped, moderately lobed or multilobed, single or in opposite pairs. Measurements were made of 35 conidiophores and 55 conormed by gently pressing the infected leaves onto 10 young leaves of three healthy plants. A non-inoculated plant was used as a control. The plants were maintained in a greenhouse at 22 to 25°C, with relative humidity around 75%, and natural light. Powdery mildew symptoms were observed on the inoculated leaves after 10-14 days, whereas no symptoms were observed on the leaves of the control. The fungi on the inoculated leaves were morphologically identical to the fungi on the original infected leaves. Erysiphe viciae-unijugae has been reported to occur on Lathyrus spp. and Vicia spp. (Farr and Rossman 2020). To our knowledge, this is the first report of powdery mildew caused by E. viciae-unijugae on V. sativa subsp. nigra in Korea. The weather conditions, especially during May, are favorable for disease outbreaks. This disease may be a potential threat to feed production in Korea.In September of 2018, onion plants (Allium cepa cv. Joaquin) grown in one field in southwest Idaho were observed to have roots with brown discoloration over 10-20% of the total root surface area. Approximately 10% of plants over a 1 ha area were affected and these plants were about visually 50% smaller than the typical bulb size present in the field. To determine the causal agent, 3 mm pieces of symptomatic roots from four plants were placed in sodium hypochlorite (2%) for one minute, followed by two rinses in sterile water and plated on to water agar medium amended with penicillin G (0.2 g/liter) and streptomycin sulfate (0.8 g/liter). After 3 days at 21°C, fungal colonies with septate hyphae with right-angled branching resembling Rhizoctonia solani were observed in over half of the 16 isolations attempted. Species identity was confirmed through rDNA ITS sequencing, as described previously (Woodhall et al., 2013), with DNA obtained from a single representative hyphal tip culture grown on Potato Dextrose Agarsuccessfully isolated from seven plant samples onto water agar. Sequencing was used to confirm identity as AG2-2IIIB. To our knowledge, this is the first report of R. solani AG 2-2 IIIB affecting onions in Idaho. Previous work in the Pacific Northwest recovered R. solani AG2-1, 3, 4 and 8 and also BNR AG A from stunted onions (Patzek et al., 2013). In Japan, Misawa et al. (2017) found AG 2-2 IIIB to be pathogenic to Welsh onion (Allium fistulosum). In Idaho, R. solani AG 2-2 IIIB has was previously reported causing disease in sugar beets (Strausbaugh et al. 2011) and potatoes (Woodhall et al. 2012). Growers should consider crop rotation strategies or soil treatments if R. solani AG2-2IIIB is causing disease in their crops.Erwinia amylovora is a plant-pathogenic bacterium that causes the fire blight disease in Rosaceae plants. Since fire blight is highly contagious and results in serious losses once introduced, it is regulated as a quarantine disease. Recently, for the first time in East Asia, fire blight emerged in Korea with strains of E. amylovora being isolated from lesions of infected trees. Five of those strains were selected and subjected to whole-genome shotgun sequencing. Each strain had two circular replicons, a 3.8-Mb chromosome and a 28-kb plasmid. The genome sequences were compared with those of other E. amylovora strains isolated from different hosts or geographical regions. Genome synteny was analyzed and sequence variations including nucleotide substitutions, inversions, insertions, and deletions were detected. Analysis of the population genomic structure revealed that the five strains form a distinct structural group. Phylogenomic analysis was performed to infer the evolutionary relationships among E. amylovora strains, which indicated that the Korean isolates, all descended from a common ancestor, are closely related to a lineage of North American strains. These results provide useful information for understanding the genomic dynamics of E. amylovora strains including those in Korea, developing genetic markers for surveillance of the pathogen or diagnosis of the disease, and eventually developing measures to eradicate it.