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

Weed Management Programs in Grain Sorghum (Sorghum bicolor)

A field study was conducted in Arkansas over three years to evaluate various herbicide treatments, including sequential and tank-mix applications for weed control in grain sorghum (Sorghum bicolor). The herbicide treatments used were quinclorac, atrazine + dimethenamid-p, S-metolachlor followed by (fb) atrazine + dicamba, dimethenamid-p fb atrazine, S-metolachlor + atrazine fb atrazine, S-metolachlor + mesotrione, and S-metolachlor fb prosulfuron. All herbicide treatments provided excellent (90% to 100%) control of Ipomoea lacunosa, Ipomoea hederacea var. integriuscula, and Sida spinosa by 12 weeks after emergence. Quinclorac and S-metolachlor fb prosulfuron provided the lowest control of Ipomoea lacunosa, Urochloa platyphylla, Amaranthus palmeri, and Ipomoea hederacea var. integriuscula. Weed interference in the non-treated control reduced grain sorghum yield by 50% as compared to the weed-free control. S-metolachlor + mesotrione and S-metolachlor fb prosulfuron reduced sorghum yields by 1009 to 1121 kg ha−1 compared to other herbicide treatments. The five best herbicide treatments in terms of weed control and grain sorghum yield were quinclorac, atrazine + dimethenamid-p, S-metolachlor fb atrazine + dicamba, dimethenamid-p fb atrazine, and the standard treatment of S-metolachlor + atrazine fb atrazine

, sp. nov., is an emerging root-associated pathogen responsible for taproot decline of soybean in the southern United States

Taproot decline (TRD) is a disease of soybean that has been reported recently from the southern United States (U.S.). Symptoms of TRD include foliar interveinal chlorosis followed by necrosis. Darkened, charcoal-colored areas of thin stromatic tissue are evident on the taproot and lateral roots along with areas of necrosis within the root and white mycelia within the pith. Upright stromata typical of can be observed on crop debris and emerging from infested roots in fields where taproot decline is present, but these have not been determined to contain fertile perithecia. Symptomatic plant material was collected across the known range of the disease in the southern U.S., and the causal agent was isolated from roots. Four loci, ⍺-actin (), β-tubulin (), the nuclear rDNA internal transcribed spacers (nrITS), and the RNA polymerase subunit II (), were sequenced from representative isolates. Both maximum likelihood and Bayesian phylogenetic analyses showed consistent clustering of representative TRD isolates in a highly supported clade within the species complex in the HY clade of the family Xylariaceae, distinct from any previously described taxa. In order to understand the origin of this pathogen, we sequenced herbarium specimens previously determined to be based on morphology and xylariaceous endophytes collected in the southern U.S. Some historical specimens from U.S. herbaria collected in the southern region as saprophytes as well as a single specimen from Martinique clustered within the TRD clade in phylogenetic analyses, suggesting a possible shift in lifestyle. The remaining specimens that clustered within the family Xylariaceae, but outside of the TRD clade, are reported. Both morphological evidence and molecular evidence indicate that the TRD pathogen is a novel species, which is described as

Comparison of Herbicides for Control of Diclofop-Resistant Italian Ryegrass in Wheat

Diclofop-resistant Italian ryegrass (Lolium perenne L. ssp. Multiflorum (Lam.) Husnot) is a dominant weed problem in non-irrigated winter wheat (Triticum aestivum L.) in mid-south USA. Field studies were conducted from 2001 to 2007 to evaluate the efficacy of herbicides for diclofop-resistant ryegrass control and effect on wheat yield. In 2001 through 2004, chlorsulfuron/metsulfuron at 0.026 kg ha−1 preemergence (PRE) followed by (fb) mesosulfuron at 0.048 kg ha−1 at 4-leaf to 2-tiller ryegrass provided 89% control of diclofop-resistant Italian ryegrass, resulting in the highest wheat yield (3201 kg ha−1). Flufenacet/metribuzin at 0.476 kg ha−1 applied at 1- to 2-leaf wheat had equivalent Italian ryegrass control (87%), but lesser yield (3013 kg ha−1). In 2005–2006, best treatments for Italian ryegrass control were chlorsulfuron/metsulfuron, 0.013 kg ha−1 PRE fb mesosulfuron 0.015 kg ha−1 at 3- to 4-leaf ryegrass (92%); metribuzin, 0.280 kg ha−1 at 2- to 3- leaf wheat fb metribuzin at 2- to 3-tiller ryegrass (94%); chlorsulfuron/metsulfuron (0.026 kg ha−1) (89%); and flufenacet/metribuzin at 1- to 2-leaf wheat (89%). Chlorsulfuron/metsulfuron fb mesosulfuron provided higher yield (3515 kg ha−1) than all other treatments, except metribuzin fb metribuzin

Draft genome sequence of Xylaria sp., the causal agent of taproot decline of soybean in the southern United States

The draft genome of Xylaria sp. isolate MSU_SB201401, causal agent of taproot decline of soybean in the southern U.S., is presented here. The genome assembly was 56.7 Mb in size with an L50 of 246. A total of 10,880 putative protein-encoding genes were predicted, including 647 genes encoding carbohydrate-active enzymes and 1053 genes encoding secreted proteins. This is the first draft genome of a plant-pathogenic Xylaria sp. associated with soybean. The draft genome of Xylaria sp. isolate MSU_SB201401 will provide an important resource for future experiments to determine the molecular basis of pathogenesis