Selection of Winter Wheat Mutant Lines Resistant to Drought Stress

Mutated winter wheat lines were screened for improved drought resistance compared to the wildtype by withholding water for 3 weeks after 9 weeks of normal growth, and noting their responses upon re-watering. Of the 146 mutants grown, 73% were either killed due to water stress or showed poor recovery, while 27% recovered better than the wildtype line. This experiment enabled the selection of candidates for further investigation to better understand the genetic basis of drought tolerance in winter wheat

Optimization and Application of a Quantitative Polymerase Chain Reaction Assay to Detect Diaporthe Species in Soybean Plant Tissue

Diaporthe caulivora and D. longicolla are the causal agents of stem canker of soybean (Glycine max L.). Accurate identification of stem canker pathogens upon isolation from infected soybean plants is difficult and unreliable based on morphology. In this study, two TaqMan probe-based quantitative polymerase chain reaction (qPCR) assays were optimized for detection of D. caulivora and D. longicolla in soybean plants. The assays used previously reported D. caulivora-specific (DPC-3) and D. longicolla-specific (PL-3) probe/primer sets. The sensitivity limit of the two assays was determined to be over a range of 100 pg to 10 fg of pure D. caulivora and D. longicolla genomic DNA. The qPCR assays were validated with plant samples collected from commercial soybean fields. The PL-3 set detected D. longicolla in soybean plants collected from the fields (quantification cycle value \u3c35), which was confirmed by isolation on potato dextrose agar (PDA). D. caulivora was detected only in low levels (quantification cycle value \u3c40) by DPC-3 set in a few of the symptomatic field samples, although the pathogen was not isolated on PDA. The qPCR assays were also useful in quantitatively phenotyping soybean plants for resistance to D. caulivora and D. longicolla under greenhouse conditions

Characterization of species of Fusarium causing root rot of Soybean (Glycine max L.) in South Dakota, USA

In 2014, 2000 plants showing root rot symptoms were collected from 200 commercial soybean (Glycine max L.) fields in South Dakota, USA. One thousand one hundred thirty fungal isolates obtained from the samples were identified as Fusarium species by morphology and sequencing of the translation elongation factor 1-alpha gene. Fifty-one percent were F. graminearum, 30.0% were F. acuminatum, 8.0% belonged to the F. oxysporum species complex, 3.4% were F. armeniacum, 2.0% were F. proliferatum, 1.6% were F. virguliforme, 1.2% belonged to the F. solani species complex, 0.4% were F. nanum (syn. F. incarnatum-equiseti species complex), 0.1% were F. bulbicola (syn. F. fujikuroi species complex) and 0.1% were F. commune. The pathogenicity of 57 isolates was evaluated on the soybean 'Asgrow 1835' under greenhouse conditions. Root rot severity was rated 14 days after inoculation on a 1-to-5 scale and expressed as relative treatment effects (RTE). Nine isolates of F. oxysporum, and one each of F. armeniacum and F. commune, caused significantly greater RTE than in the non-inoculated control. Twenty-one accessions were screened for resistance in the greenhouse using one isolate each of F. graminearum, F. proliferatum and F. sporotrichioides. Accession PI361090 was less susceptible to F. graminearum and F. proliferatum than the susceptible controls, 'Williams 82' and 'Asgrow 1835'. All accessions were more susceptible to F. sporotrichioides. These findings suggest that 11 Fusarium species or species complexes are pathogenic to soybean in South Dakota, and PI361090 may be a useful source of resistance to F. graminearum and F. proliferatum

Six species of Diaporthe associated with Phomopsis stem canker of sunflower in southern Pampean region of Argentina

A survey of 67 commercial fields in 19 locations was conducted in the southern Pampean region of Argentina for Phomopsis stem canker of sunflower (Helianthus annuus L.) between 2014 and 2019. A total of 210 plants having typical symptoms of Phomopsis stem canker were randomly sampled, and fungal isolation was performed. Of the 187 isolates of Diaporthe that were recovered, 94% of the isolates showed morphological characteristics similar to D. helianthi, 3% to D. gulyae, 1% to D. caulivora, 1% to D. sojae, 0.5% to D. kongii, and 0.5% to D. longicolla. Following morphological characterization, the identity of the six morpho-species was confirmed by phylogenetic analyses of b-tubulin, translation elongation factor 1-a, and internal transcribed spacer gene regions. Koch’s postulates were completed for the six fungi by inoculating one susceptible sunflower hybrid with one isolate each of the six species of Diaporthe using the stem-wound inoculation method. Seven days postinoculation, significant differences in disease severity were observed between the six isolates (P < 0.0001), with D. helianthi and D. gulyae isolates causing significantly greater disease severity. To our knowledge, this is the first report of D. kongii, D. longicolla, D. caulivora, and D. sojae associated with Phomopsis stem canker of sunflower in Argentina.Fil: Zambelli, Andres Daniel. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; ArgentinaFil: Mancebo, María F.. Advanta Semillas S.A.I.C.; ArgentinaFil: Bazzalo, María E.. Advanta Semillas S.A.I.C.; ArgentinaFil: Reid, Roberto J.. Advanta Semillas S.A.I.C.; ArgentinaFil: Sanchez, María C.. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; ArgentinaFil: Kontz, Brian J.. South Dakota State University; Estados UnidosFil: Mathew, Febina M.. South Dakota State University; Estados Unido

Root Rot Caused by Species of Fusarium on Brassica carinata in South Dakota

Brassica carinata is an emerging oilseed crop in the United States, and root diseases caused by Fusarium have the potential to cause yield losses in production. In this study, B. carinata plants were randomly sampled at vegetative and seed development plant stages from South Dakota State University experimental plots. Reddish-brown lesions were observed on roots of sampled plants from which F. acuminatum, F. oxysporum, F. solani, and F. sporotrichioides were recovered. The Fusarium species were identified based on morphology and phylogenetic analyses of the translation elongation factor 1-alpha gene region. Pathogenicity of the four Fusarium species was evaluated on five B. carinata accessions using a modified inoculum layer method in the greenhouse. At 21 days after inoculation, root rot severity caused by Fusarium on the B. carinata accessions was assessed on a rating scale of 0 to 4 and evaluated using relative treatment effects (RTEs). The F. oxysporum isolate caused significant differences in RTE (P = 0.01) among the B. carinata accessions. However, there were no significant differences in RTE among the B. carinata accessions in response to F. acuminatum (P = 0.82), F. solani (P = 0.76), and F. sporotrichioides (P = 0.47) isolates

Sustainability transition of pesticide use practices: behavioural dynamics and policy options

One hundred fifty-two Diaporthe isolates were recovered from symptomatic soybean (Glycine max) stems sampled from the U.S. states of Iowa, Indiana, Kentucky, Michigan, and South Dakota. Using morphology and DNA sequencing, isolates were identified as D. aspalathi (8.6%), D. caulivora (24.3%), and D. longicolla (67.1%). Aggressiveness of five isolates each of the three pathogens was studied on cultivars Hawkeye (D. caulivora and D. longicolla) and Bragg (D. aspalathi) using toothpick, stem-wound, mycelium contact, and spore injection inoculation methods in the greenhouse. For D. aspalathi, methods significantly affected disease severity (P \u3c 0.001) and pathogen recovery (P \u3c 0.001). The relative treatment effects (RTE) of stem-wound and toothpick methods were significantly greater than for the other methods. For D. caulivora and D. longicolla, a significant isolate × method interaction affected disease severity (P \u3c 0.05) and pathogen recovery (P \u3c 0.001). Significant differences in RTEs were observed among D. caulivora and D. longicolla isolates only when the stem-wound and toothpick methods were used. Our study has determined that the stem-wound and toothpick methods are reliable to evaluate the three pathogens; however, the significant isolate × method interactions for D. caulivora and D. longicolla indicate that multiple isolates should also be considered for future pathogenicity studies