Proceedings of the 47th Annual Meeting, Southern Soybean Disease Workers (March 4-5, 2020, Pensacola Beach, Florida)

Contents Southern United States soybean disease loss estimates for 2019. TW Allen, K Bissonnette, CA Bradley, JP Damicone, NS Dufault, TR Faske, T Isakeit, RC Kemerait, A Koehler, HL Mehl, JD Mueller, GB Padgett, PP Price, EJ Sikora, IM Small, L Thiessen, and H Young Abstracts of presented papers Fungicide efficacy on target spot in Tennessee soybean. Ty Smith, H Kelly, and Z Hansen Temporal dynamics of Neohydatothrips variabilis, Frankliniella tritici, and Frankliniella fusca in South Central Wisconsin and the occurrence of Soybean vein necrosis virus. Cristina Zambrana-Echevarria, S Kaplan, RL Groves, and DL Smith Population distributions and densities of nematodes, and virulence phenotypes of soybean cyst nematode in Tennessee. Rufus Akinrinlola, and H Kelly Improving soybean white mold control by integrated management. Wade Webster, B Mueller, J Gaska, D Mueller, MI Chilvers, S Conley, and DL Smith Assessment of QoI sensitivity and frogeye leaf spot race of Cercospora sojina in Georgia soybean. Bennett Harrelson, A Culbreath, R Kemerait, Jr, and J Buck Reduction of Pythium damping-off in soybean by biocontrol seed treatment. Mirian F Pimentel, E Arnao, A Warner, N Elsharif, M Chilvers, A Robertson, J Bond, and A Fakhoury Understanding cercosporin self-resistance to identify novel tools to manage Cercospora leaf blight on soybean. Maria Izabel Costa de Novaes, CL Robertson, VP Doyle, and S Thomas-Sharma Evaluating the efficacy of soybean seed treatment on high and low vigor seed in Arkansas. Samantha Segalin, JC Rupe, JA Rojas, and R Holland Impact of wheat on soybean cyst nematode (Heterodera glycines I.) populations in a soybean double cropping system. Leonardo F Rocha, MF Pimentel, JP Bond, and AM Fakhoury Using unmanned aerial systems and multispectral imagery to assess sudden death syndrome of soybean. Lindsey McKinzie, AM Fakhoury, R Li, and JP Bond Soybean rust: Scourge of Alabama. Ed J Sikora, D Delaney, and K Connor Management of SCN and SDS with nematode-protectant seed treatments across multiple environments. Kaitlyn M Bissonnette, Y Kandel, M Chilvers, N Kleczewski, D Mueller, D Smith, D Telenko, and A Tenuta Determining inoculum density of Xylaria sp., the taproot decline pathogen, in soil under various crop rotation systems. Aline Bronzato-Badial, K Phillips, TH Wilkerson, and M Tomas-Peterson A new pathosystem to study the plant-fungal interactions underlying Cercospora leaf blight of soybean. Kona Swift and B Bluhm Impact of cultivar on soybean foliar and seed diseases in Arkansas. John C Rupe, RT Holland, and JA Rojas Thoughts on southern blight: Should we be concerned about southern blight? Tom W Allen, WL Solomon, and BA Burgess From plots to strips: Six years of fungicide trials. Terry N Spurlock, AC Tolbert, and RC Hoyle Meta-analysis of soybean yield response to foliar fungicides evaluated from 2005 to 2018 in the United States and Canada. Yuba K Kandel, C Hunt, K Ames, N Arneson, CA Bradley, E Byamukama, A Byrne, MI Chilvers, L Giesler, J Halvorson, DC Hooker, NM Kleczewski, DK Malvick, S Markell, B Potter, W Pederson, DL Smith, AU Tenuta, DEP Telenko, KA Wise, and DS Mueller On the road in Louisiana: Taking the research station to farms. Trey Price, MA Purvis, DA Ezell, GB Padgett, M Foster, and J Hebert The next super model: Development of a flexible framework for multiple disease models in soybean. Damon L Smith, J Willbur, M Chilvers, M Kabbage, SP Conley, D Mueller, and R Schmidt IPM implementation in Tennessee. Heather M Kelly, S Stewart, K Vail, D Hensley, S Steckel, A McClure, and T Raper Reproduction potential and survival of soybean nematodes in row rice. Travis Faske, K Brown, and N Bateman Initial research with peracetic acid as a disease management tool in soybeans and other legume crops. Vijay K Choppakatla FMC fungicide offerings update. Matthew Wiggins Abstracts for presented posters Extension efforts in disseminating nematode survey results. Rachel Guyer, R Akinrinlola, and H Young Assessing the role of weathering on the grain quality of soybean varieties in the Mississippi Delta. Tessie H Wilkerson, TW Allen, and BA Burgess Proceedings of the Southern Soybean Disease Workers are published annually by the Southern Soybean Disease Workers. Text, references, figures, and tables are reproduced as they were submitted by authors. The opinions expressed by the participants at this conference are their own and do not necessarily represent those of the Southern Soybean Workers. Mention of a trademark or proprietary products in this publication does not constitute a guarantee, warranty, or endorsement of that product by the Southern Soybean Disease Workers

Proceedings of the 48th Annual Meeting, Southern Soybean Disease Workers (March 3, 2021, Virtual Content)

2021 Southern Soybean Disease Workers Agenda Virtual | Wednesday, March 3, 2021 Southern United States Soybean Disease Loss Estimates for 2020. TW Allen, K Bissonnette, CA Bradley, JP Damicone, NS Dufault, TR Faske, T Isakeit, RC Kemerait, A Koehler, D Langston, JD Mueller, GB Padgett, PP Price, EJ Sikora, IM Small, L Thiessen, and H Young Student papers (Tessie Wilkerson, moderator) Secondary metabolites produced by Xylaria necrophora are responsible for the foliar symptoms associated with taproot decline of soybean. Teddy Garcia-Aroca, Trey Price, José Solórzano, David Galo, Sophie Sheffield, Jonathan K. Richards, and Vinson P. Doyle Meta-analysis of fungicide performance for managing frogeye leaf spot on soybean in the United States. Jhonatan P Barro, Emerson M Del Ponte, Tom Allen, Jason P Bond, Travis R Faske, Clayton A Hollier, Yuba R Kandel, Daren S Mueller, Heather M Kelly, Nathan M Kleczewski, Paul Price, Edward J Sikora, and Carl A Bradley Using metagenomic tools to explore the suppression of soybean cyst nematode populations in fields double-cropped with wheat and soybean. Leonardo F Rocha, Jason P Bond, Ahmad M Fakhoury Investigating the effects of demethylation inhibitor fungicides and the insecticide malathion on Corynespora cassiicola. Ty Smith, Heather Kelly, and Larry Steckel DNA-based protocol for rapid detection of QoI (Strobilurin) fungicide resistance in Cercospora sojina and a statewide survey of foliar fungicide use for soybean disease management in Nebraska. Asha Mane, Tamra Jackson-Ziems, Carl Bradley, and Syndney Everhart Assessing Missouri soybean fields for fungicide-resistant Cercospora sojina. Bruna Just, and Kaitlyn M Bissonnette Contributed papers (Trey Price, moderator) Observations from soybean rust monitoring and fungicide field demonstrations in Alabama in 2020. Edward J Sikora and Kassie Conner Field performance of two new commercially available premix fungicides for management of foliar disease of soybean in Arkansas. Terry N Spurlock, Robert C Hoyle, Sydney F Kling, and Amanda C Tolbert The impact of different crop rotations on soilborne microbial diversity and disease emergence of soybean-corn cropping system. Qiurong Fan, Travis Faske, Terry Spurlock, Alejandro Rojas and Trent Roberts SCN Coalition: Updates and Evolution. Sam Markell and Albert Tenuta Evaluating varieties in the Mississippi State University Official Variety Trial Program for the presence and severity of green stem. Tom Allen, Walter Solomon, and Brad Burgess Proceedings of the Southern Soybean Disease Workers are published annually by the Southern Soybean Disease Workers. Text, references, figures, and tables are reproduced as they were submitted by authors. The opinions expressed by the participants at this conference are their own and do not necessarily represent those of the Southern Soybean Workers. Mention of a trademark or proprietary products in this publication does not constitute a guarantee, warranty, or endorsement of that product by the Southern Soybean Disease Workers

Resistance to Botrytis cinerea in Solanum lycopersicoides Involves Widespread Transcriptional Reprogramming.

Background Tomato (Solanum lycopersicum), one of the world’s most important vegetable crops, is highly susceptible to necrotrophic fungal pathogens such as Botrytis cinerea and Alternaria solani. Improving resistance through conventional breeding has been hampered by a shortage of resistant germplasm and difficulties in introgressing resistance into elite germplasm without linkage drag. The goal of this study was to explore natural variation among wild Solanum species to identify new sources of resistance to necrotrophic fungi and dissect mechanisms underlying resistance againstB. cinerea. Results Among eight wild species evaluated for resistance against B. cinerea and A. solani, S. lycopersicoides expressed the highest levels of resistance against both pathogens. Resistance against B. cinerea manifested as containment of pathogen growth. Through next-generation RNA sequencing and de novo assembly of the S. lycopersicoides transcriptome, changes in gene expression were analyzed during pathogen infection. In response to B. cinerea, differentially expressed transcripts grouped into four categories: genes whose expression rapidly increased then rapidly decreased, genes whose expression rapidly increased and plateaued, genes whose expression continually increased, and genes with decreased expression. Homology-based searches also identified a limited number of highly expressed B. cinerea genes. Almost immediately after infection by B. cinerea, S. lycopersicoides suppressed photosynthesis and metabolic processes involved in growth, energy generation, and response to stimuli, and simultaneously induced various defense-related genes, including pathogenesis-related protein 1 (PR1), a beta-1,3-glucanase (glucanase), and a subtilisin-like protease, indicating a shift in priority towards defense. Moreover, cluster analysis revealed novel, uncharacterized genes that may play roles in defense against necrotrophic fungal pathogens in S. lycopersicoides. The expression of orthologous defense-related genes in S. lycopersicum after infection with B. cinerea revealed differences in the onset and intensity of induction, thus illuminating a potential mechanism explaining the increased susceptibility. Additionally, metabolic pathway analyses identified putative defense-related categories of secondary metabolites. Conclusions In sum, this study provided insight into resistance against necrotrophic fungal pathogens in the Solanaceae, as well as novel sequence resources for S. lycopersicoides

Analyses of expressed sequence tags from the maize foliar pathogen Cercospora zeae-maydis identify novel genes expressed during vegetative, infectious, and reproductive growth

<p>Abstract</p> <p>Background</p> <p>The ascomycete fungus <it>Cercospora zeae-maydis </it>is an aggressive foliar pathogen of maize that causes substantial losses annually throughout the Western Hemisphere. Despite its impact on maize production, little is known about the regulation of pathogenesis in <it>C. zeae-maydis </it>at the molecular level. The objectives of this study were to generate a collection of expressed sequence tags (ESTs) from <it>C. zeae-maydis </it>and evaluate their expression during vegetative, infectious, and reproductive growth.</p> <p>Results</p> <p>A total of 27,551 ESTs was obtained from five cDNA libraries constructed from vegetative and sporulating cultures of <it>C. zeae-maydis</it>. The ESTs, grouped into 4088 clusters and 531 singlets, represented 4619 putative unique genes. Of these, 36% encoded proteins similar (E value ≤ 10^-05) to characterized or annotated proteins from the NCBI non-redundant database representing diverse molecular functions and biological processes based on Gene Ontology (GO) classification. We identified numerous, previously undescribed genes with potential roles in photoreception, pathogenesis, and the regulation of development as well as <it>Zephyr</it>, a novel, actively transcribed transposable element. Differential expression of selected genes was demonstrated by real-time PCR, supporting their proposed roles in vegetative, infectious, and reproductive growth.</p> <p>Conclusion</p> <p>Novel genes that are potentially involved in regulating growth, development, and pathogenesis were identified in <it>C. zeae-maydis</it>, providing specific targets for characterization by molecular genetics and functional genomics. The EST data establish a foundation for future studies in evolutionary and comparative genomics among species of <it>Cercospora </it>and other groups of plant pathogenic fungi.</p

The Genome Sequence of the Fungal Pathogen Fusarium virguliforme That Causes Sudden Death Syndrome in Soybean

Fusarium virguliforme causes sudden death syndrome (SDS) of soybean, a disease of serious concern throughout most of the soybean producing regions of the world. Despite the global importance, little is known about the pathogenesis mechanisms of F. virguliforme. Thus, we applied Next-Generation DNA Sequencing to reveal the draft F. virguliforme genome sequence and identified putative pathogenicity genes to facilitate discovering the mechanisms used by the pathogen to cause this disease

Analyses of expressed sequence tags from the maize foliar pathogen Cercospora zeae-maydis identify novel genes expressed during vegetative, infectious, and reproductive growth

<p>Abstract</p> <p>Background</p> <p>The ascomycete fungus <it>Cercospora zeae-maydis </it>is an aggressive foliar pathogen of maize that causes substantial losses annually throughout the Western Hemisphere. Despite its impact on maize production, little is known about the regulation of pathogenesis in <it>C. zeae-maydis </it>at the molecular level. The objectives of this study were to generate a collection of expressed sequence tags (ESTs) from <it>C. zeae-maydis </it>and evaluate their expression during vegetative, infectious, and reproductive growth.</p> <p>Results</p> <p>A total of 27,551 ESTs was obtained from five cDNA libraries constructed from vegetative and sporulating cultures of <it>C. zeae-maydis</it>. The ESTs, grouped into 4088 clusters and 531 singlets, represented 4619 putative unique genes. Of these, 36% encoded proteins similar (E value ≤ 10^-05) to characterized or annotated proteins from the NCBI non-redundant database representing diverse molecular functions and biological processes based on Gene Ontology (GO) classification. We identified numerous, previously undescribed genes with potential roles in photoreception, pathogenesis, and the regulation of development as well as <it>Zephyr</it>, a novel, actively transcribed transposable element. Differential expression of selected genes was demonstrated by real-time PCR, supporting their proposed roles in vegetative, infectious, and reproductive growth.</p> <p>Conclusion</p> <p>Novel genes that are potentially involved in regulating growth, development, and pathogenesis were identified in <it>C. zeae-maydis</it>, providing specific targets for characterization by molecular genetics and functional genomics. The EST data establish a foundation for future studies in evolutionary and comparative genomics among species of <it>Cercospora </it>and other groups of plant pathogenic fungi.</p

Changes in the Fungal Microbiome of Maize During Hermetic Storage in the United States and Kenya

Prior to harvest, maize kernels are invaded by a diverse population of fungal organisms that comprise the microbiome of the grain mass. Poor post-harvest practices and improper drying can lead to the growth of mycotoxigenic storage fungi and deterioration of grain quality. Hermetic storage bags are a low-cost technology for the preservation of grain during storage, which has seen significant adoption in many regions of Sub-Saharan Africa. This study explored the use of high-throughput DNA sequencing of the fungal Internal Transcribed Spacer 2 (ITS2) region for characterization of the fungal microbiome before and after 3 months of storage in hermetic and non-hermetic (woven) bags in the United States and Kenya. Analysis of 1,377,221 and 3,633,944 ITS2 sequences from the United States and Kenya, respectively, resulted in 251 and 164 operational taxonomic units (OTUs). Taxonomic assignment of these OTUs revealed 63 and 34 fungal genera in the US and Kenya samples, respectively, many of which were not detected by traditional plating methods. The most abundant genus was Fusarium, which was identified in all samples. Storage fungi were detected in the grain mass prior to the storage experiments and increased in relative abundance within the woven bags. The results also indicate that storage location had no effect on the fungal microbiome of grain stored in the United States, while storage bag type led to significant changes in fungal composition. The fungal microbiome of the Kenya grain also underwent significant changes in composition during storage and fungal diversity increased during storage regardless of bag type. Our results indicated that extraction of DNA from ground kernels is sufficient for identifying the fungi associated with the maize. The results also indicated that bag type was the most important factor influencing changes in fungal microbiome during storage. The results also support the recommended use of hermetic storage for reducing food safety risks, especially from mycotoxigenic fungi

A framework for integrated environmental health impact assessment of systemic risks

Traditional methods of risk assessment have provided good service in support of policy, mainly in relation to standard setting and regulation of hazardous chemicals or practices. In recent years, however, it has become apparent that many of the risks facing society are systemic in nature – complex risks, set within wider social, economic and environmental contexts. Reflecting this, policy-making too has become more wide-ranging in scope, more collaborative and more precautionary in approach. In order to inform such policies, more integrated methods of assessment are needed. Based on work undertaken in two large EU-funded projects (INTARESE and HEIMTSA), this paper reviews the range of approaches to assessment now in used, proposes a framework for integrated environmental health impact assessment (both as a basis for bringing together and choosing between different methods of assessment, and extending these to more complex problems), and discusses some of the challenges involved in conducting integrated assessments to support policy

How ice grows from premelting films and water droplets

Close to the triple point, the surface of ice is covered by a thin liquid layer (so-called quasi-liquid layer) which crucially impacts growth and melting rates. Experimental probes cannot observe the growth processes below this layer, and classical models of growth by vapor deposition do not account for the formation of premelting films. Here, we develop a mesoscopic model of liquid-film mediated ice growth, and identify the various resulting growth regimes. At low saturation, freezing proceeds by terrace spreading, but the motion of the buried solid is conveyed through the liquid to the outer liquid-vapor interface. At higher saturations water droplets condense, a large crater forms below, and freezing proceeds undetectably beneath the droplet. Our approach is a general framework that naturally models freezing close to three phase coexistence and provides a first principle theory of ice growth and melting which may prove useful in the geosciences.Comment: 32 pages, 10 figure

Regulation of fumonisin biosynthesis in the maize kernel

Fusarium verticillioides is a ubiquitous fungal pathogen of agriculturally important commodities throughout the world. During the colonization of maize (Zea mays) kernels, F. verticillioides produces toxic secondary metabolites known as fumonisins. Fumonisins cause a range of species-specific health effects when ingested and are suspected to cause cancer and birth defects in humans. Despite enormous economic impacts associated with fumonisin contamination of grain, very little is known about how fumonisin biosynthesis is regulated during kernel colonization. My research focused on elucidating the interaction between F. verticillioides and maize that results in the accumulation of fumonisins in maize kernels. To this end, I identified FCK1, a gene encoding a cyclin-dependent kinase in F. verticillioides. Disruption of FCK1 resulted in pleiotropic morphological defects, including reduced growth, conidiation, fumonisin B1 (FB 1) production, and enhanced pigmentation. Additionally, I identified amylopectin, a component of maize kernel starch, as a key inducer of FB 1 biosynthesis during kernel colonization. Kernels lacking starch due to physiological immaturity did not accumulate FB1, and a mutant strain of F. verticillioides with a disrupted α-amylase gene was impaired in its ability to produce FB1 on kernels containing starch. Both the wild-type and mutant strains produced significantly less FB1 on a high-amylose kernel mutant of maize. When grown on a defined medium with amylose as the sole carbon source, the wild-type strain produced only trace amounts of FB1, but it produced large amounts of FB 1 when grown on amylopectin or dextrin, a product of amylopectin hydrolysis. Finally, I determined that disruption of ZFR1, a putative transcriptional regulator, blocked the induction of fumonisin biosynthesis by amylopectin and affected the transcription of genes involved in starch hydrolysis and carbohydrate uptake. From these findings, a new model has been developed to explain how FB1 biosynthesis is regulated during kernel colonization. The model highlights new avenues to unravel the complex interactions underlying colonization of maize kernels by F. verticillioides and could give rise to innovative strategies to control fumonisin accumulation in maize