Download or read book The Soybean Seedling Disease Complex written by Margaret Lee Ellis and published by . This book was released on 2011 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Seedling diseases in soybean fields in Ohio have increased over the past decade. This study was conducted to better characterize some of these seedling pathogens, specifically Fusarium graminearum and two new pathogenic species of Pythium, as well as evaluate management strategies, particularly host resistance, for F. graminearum and Pythium irregulare. A rolled towel assay was developed to understand the potential impact of F. graminearum as a soybean pathogen by evaluating the effect of inoculum density, temperature parameters, and fungicide seed treatments on disease development. Inoculum concentrations of 2.5 x 104 macroconidia/ml or higher were necessary for disease development at temperatures 18 to 25°C, indicating that high levels of inoculum may be necessary for disease to occur. Seed treated with captan at 61.9 g a.i. or fludioxonil at 2.5 or 5.0 g a.i. per 100 kg developed smaller lesions than other seed treatments and the non-treated control. The rolled towel assay was used to screen 24 soybean genotypes for resistance to F. graminearum. Five genotypes had high levels of resistance to F. graminearum, including the cultivar Conrad, a major source of partial resistance to Phytophthora sojae. A population of 262 F6:8 recombinant inbred lines (RIL) derived from a cross of Conrad x Sloan (Susceptible) was evaluated for resistance and segregated as a quantitative trait. Four putative quantitative trait loci (QTLs) were identified from Conrad on chromosomes 8, 13, 15, and 16, and one putative QTL from Sloan on chromosome 19. The putative QTLs identified in this population did not map to the same regions that confer resistance to Ph. sojae, suggesting different mechanisms are required for these two seedling pathogens. In this study, two new species of Pythium, P. schmitthenneri and, P. selbyi, were described using morphology and sequence analysis of the ITS1-5.8S-ITS2 region. These new species were recovered from 30% of fields surveyed which was focused on the identification of seedling pathogens; they are both pathogens to corn and soybean. Pythium irregulare is one of the most widespread Pythium species in Ohio soybean fields and has very high levels of pathogenicity. In a greenhouse assay, 105 soybean genotypes were evaluated for resistance to two isolates of P. irregulare. Isolate x genotype interaction for root weight and rot root score was not significant. The plant introduction (PI) 424354 had high levels of resistance to P. irregulare. Two BC1F2:3 populations were used to map the resistance including: 192 lines of OHS 303 (moderately susceptible) x (Williams (susceptible) x PI 424354) and 127 lines of Dennison (moderately susceptible) x (Williams x PI 424354). Both populations fit the model for quantitative resistance based on root weight and root rot score. Putative QTL were identified on chromosomes 1, 5, 6, 8, 10, 11, 13, 14, and 20. These results suggest PI 424354 can be an important source of partial resistance in developing germplasm for breeding new cultivars with more durable resistance to P. irregulare.

Download or read book Effect of Soil applied Protoporphyrinogen Oxidase Inhibitor Herbicides on Soybean Seedling Disease written by Nicholas J. Arneson and published by . This book was released on 2019 with total page 117 pages. Available in PDF, EPUB and Kindle. Book excerpt: Seedling disease is one the most economically important diseases of soybean in the United States. It is commonly caused by Fusarium spp., Rhizoctonia solani, Pythium spp., and Phytophthora sojae, alone, or together as a disease complex. Fungicide seed treatments continue to provide the most consistent management of seedling diseases. Soil-applied protoporphyrinogen oxidase (PPO) inhibitor herbicides are used preemergence in soybean production to manage several broadleaf weeds. Applications of PPO-inhibitors can result in phytotoxic injury to soybean when environmental conditions are not favorable for soybean growth. These environmental conditions can favor seedling disease development as well. In this thesis, two studies were conducted to determine the effect of soil-applied PPO-inhibitors on soybean seedling disease development in Nebraska under field and controlled conditions. The first study assessed the effect of two PPO-inhibitors and a fungicide seed treatment on seedling disease and yield in 9 soybean fields in Nebraska. PPO-inhibitor injury occurred at 7 of 9 locations with inconsistent effects on seedling disease, where increases in root rot severity of 6.6-28.1% were observed at 5 of 9 locations, decreases of 4.7-10.9% at two locations, and no effect at three locations. None of these effects impacted yield at any of the locations. Fungicide seed treatment did not reduce root rot severity at any location; however, it increased yield at two locations. The second study investigated the effect of PPO-inhibitors on seedling disease caused by Fusarium solani under controlled conditions. Disease pressure was consistent throughout this study, with root rot severities ranging 32.1-38.9%. PPO-inhibitor injury occurred in all experiments with severities ranging 7.0-33.0%. Sulfentrazone alone increased root rot severity 9-12%. There was an effect of PPO-inhibitors on seedling disease development, although results were inconsistent, indicating a need for further research. PPO-inhibitors should continue to be used in part of an integrated weed management program and fungicide seed treatments should be used in fields that have a history of seedling disease.

Download or read book Rhizoctonia Species Taxonomy Molecular Biology Ecology Pathology and Disease Control written by B. Sneh and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 561 pages. Available in PDF, EPUB and Kindle. Book excerpt: Rhizoctonia Species: Taxonomy, Molecular Biology, Ecology, Pathology and Control, written by the world's most reputable experts in their respective fields of Rhizoctonia research, summarizes years of research in the various aspects of the ubiquitous complex group of soil-borne fungi belonging to the anamorph genus Rhizoctonia. Species of Rhizoctonia worldwide cause economically important diseases on most of the world's important plants such as cereals, potato, cotton, sugarbeet, vegetables, ornamentals and trees in nurseries. The subject reviews covered in the book include classic as well as modern approaches to Rhizoctonia research in: Taxonomy and Evolution, Genetics and Pathogenicity, Plant-Rhizoctonia Interactions, Ecology, Population and Disease Dynamics, Disease Occurrence and Management in Various Crops, Cultural Control, Biological Control, Germplasm for Resistance, Chemical and Integrated Control Strategies. It aims to be the standard reference source book on Rhizoctonia for the next decade or more, just as Parmeter et al. (1970) has been in the past. It will be an important publication for Rhizoctonia investigators, plant pathologists, students, extension specialists, crop producers and companies dealing with plant disease control.

Download or read book Epidemiology and Etiology of Soybean Seedling Disease Ecology of Seedling Disease Fungi and Evaluation of Fusarium Solani Pathogenicity to Soybean Seedlings written by Joseph Frank Killebrew and published by . This book was released on 1987 with total page 128 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Development of Soybean Seedling Diseases in Natural Infested Soils at Three Temperatures written by Keiddy Esperanza Urrea Romero and published by . This book was released on 2010 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Soybean Seedling Diseases written by Frank Killebrew and published by . This book was released on 1983 with total page 2 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Soybean Seedling Diseases written by W.F. Moore and published by . This book was released on 1990 with total page 2 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Soybean Diseases written by Denis C. McGee and published by American Phytopathological Society. This book was released on 1992 with total page 164 pages. Available in PDF, EPUB and Kindle. Book excerpt: Diseases that are seedborne and seed transmitted; Fungi; Ascochyta leaf spot; Anthracnose; Curvularia cotyledon spot; Downy mildew; Frogeye leaf spot; Phomopsis seed decay; Purple seed stain; Sclerotinia stem rot; Bacteria; Bacterial blight; Bacterial pustule; Bacterial tan spot; Bacterial wilt; Corynebacterium wilt; Wildfire; Viruses; Alfalfa mosaic; Bean pod mottle; Brazilian bud blight; Bud blight; Cowpea mild mottle; Cucumber mosaic; Peanut stunt; Peanut stripe; Soybean mild mosaic; Soybean mosaic; Soybean stunt; Tomato ringspot; Diseases that are seedborne but not seed transmitted; Fungi; Altenaria leaf spot; Botrytis stem rot; Brown spot; Brown stem rot; Charcoal rot; Drechslera blight; Fusarium pod and collar rot; Fusarium root rot; Fusarium wilt; Myrothecium leaf spot; Phyllosticta leaf spot; Phytophthora root rot; Pythium root rot; Rhizoctonia aerial blight; Rhizoctonia root rot; Stem canker; Southern blight; Storage rot; Target spot, Thielaviopsis root rot; Verticillium stem rot; Yeast spot; Bacteria; Bacillus seed decay; Chocolate spot; Viruses; Southern bean mosaic; Diseases that are not seedborne or seed transmitted; Fungi; Choanephora leaf blight; Leptosphaerulina leaf spot; Mycoleptodiscus root rot; Neocosmospora stem rot; Powdery mildew; Red crown rot; Red leaf blotch; Scab; Soybean rust; Stemphylium leaf blight; Sudden death syndrome; Bacteria; Bacterial crinkle leaf spot; Pseudomonas andropogonis leaf spot; Mycoplasmas; Bud proliferation; Machismo; Witches' broom; Viruses; Abutilion mosaic; African soybean dwarf; Azuki mosaic; bean chlorotic ringspot; Bean common mosaic; Bean yellow mosaic; Black gram mottle; Blackeye cowpea mosaic; Cowpea aphid-borne mosaic; Cowpea chlorotic mottle; Cowpea mosaic; Cowpea severe mosaic; Crinkle leaf; Indonesian soybean dwarf; Mung bean yellow mosaic; Peanut mottle; Rhyncosia mosaic; Rosette; Soybean chlorotic mottle; Soybean dwraf; Soybean severe stunt; Soybean yellow vein; Tobacco mosaic; Tomato spotted wilt.

Download or read book Soybean Seedling Diseases written by William Fred Moore and published by . This book was released on 1992 with total page 2 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Soil Amendment Soybean Seedling Disease Control written by Abraham Dalu and published by . This book was released on 1987 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Diversity of Oomycetes Associated with Soybean Seedling Diseases written by Jorge Alejandro Rojas-Flechas and published by . This book was released on 2016 with total page 265 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Seedling Diseases of Soybean in Northeast Louisiana written by John Robert Frantom and published by . This book was released on 1977 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effect of Soybean Seed Treatments on Oomycete Evolution and Diversity for Improved Seedling Disease Management written by Zachary Albert Noel and published by . This book was released on 2019 with total page 139 pages. Available in PDF, EPUB and Kindle. Book excerpt: Soybean (Glycine max L.) is the second most important crop in the United States. Soil conservation efforts combined with earlier planting dates has led to increased crop residue and cooler soil at planting. This exposes seeds and developing seedlings to adverse conditions for extended periods of time, which can increase disease pressure from many oomycete pathogens causing pre- or post-emergence damping-off. In North America, at least 84 oomycete species within the genera Pythium, Phytophthora, Phytopythium, and Aphanomyces are associated with soybean seedlings. The number of oomycete species makes management decisions difficult and seed applied anti-oomycete chemicals (oomicides) are the primary management tool against the majority of these species. Therefore, the overall theme of this dissertation was to determine the effect of soybean seed treatments on oomycete evolution and diversity to improve management recommendations. First, in chapter 1, I provide a review of current literature and background information on soybean seedling disease management, fungicide (including oomicide) resistance theory, Peronosporalean taxonomy and evolution, and review current methods to study oomycete diversity. Secondly, since an essential step in monitoring for oomicide resistance is in vitro testing, I provide clarification of terms and models involved in the analysis of in vitro dose-response data for improved reproducibility (chapter 2). Next, in chapter 3, the level of interspecific variation in mefenoxam and ethaboxam sensitivity was determined using a newly developed high-throughput assay for oomycetes that utilized growth curves and Z'-factor for quality control. This revealed that that interspecific variation in sensitivity to ethaboxam was greater than mefenoxam. Therefore, in chapter 4, the genetic and evolutionary mechanism of ethaboxam insensitivity was investigated. This revealed for the first time that inherent insensitivity to ethaboxam was linked to the convergent evolution of a specific substitution in the target gene, which resulted in lineage-specific insensitivity to ethaboxam. In chapter 5, the effect of location, and seed treatments containing either mefenoxam or ethaboxam and metalaxyl on the recovery of oomycetes from soybean taproot or lateral root tissue. This study demonstrated that oomycete communities were largely structured by location and that the recovery oomycetes from soybeans were dependent on the unique combination of location, tissue, and seed treatment. Finally, in chapter 6, an oomycete metabarcoding approach (amplicon sequencing) was used to study the influence of soybean seed treatment and genotype on oomycete rhizosphere diversity from a location with or without a history of seedling disease. This indicated that oomycete community diversity was driven by location and that an imbalance of oomycete taxa rather than simply the presence-absence of certain taxa might be responsible for differences in disease pressure. Additionally, there was no substantial evidence that genotype or seed treatment influenced oomycete diversity in soybean rhizosphere samples. Finally, in chapter 7, I discuss the overall conclusions and impacts of the studies presented herein. Overall, data from these studies provide essential new information for the management of oomycete communities with soybean seed treatments. Importantly, these studies advance our knowledge about the effect of soybean seed treatments on the evolution and diversity of oomycetes in a soybean agroecosystem.

Download or read book The Effects of Preemergence Herbicides on Soybean Seedling Diseases written by Thomas Gordon Julius and published by . This book was released on 1969 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Integrated Management of Phytophthora Stem and Root Rot of Soybean and the Effect of Soil applied Herbicides on Seedling Disease Incidence written by Vinicius Castelli Garnica and published by . This book was released on 2019 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt: Soybean seedling diseases and Phytophthora stem and root rot (PSRR; caused by Phytophthora sojae) are two of the most economically important diseases in North Central U.S. Remarkable differences in disease incidence occur each year, which demonstrate that abiotic and biotic factors must interact for disease onset and development. During 2017 and 2018, field studies were conducted to (i) address the efficacy of seed treatment and genetic resistance for PSRR management on soybean population, canopy coverage (CC), and yield, and (ii) investigate potential interactions between pre-emergence (PRE) herbicides and the incidence of seedling diseases in alluvial soils in Nebraska. Despite field history, PSRR developed in only four of six environments studied. Commercial seed treatment had a positive effect on plant population density, CC, and yield in at least three environments. Compared to non-treated control, seed treatment increased emergence between 11,600 to 53,700 plants ha-1 and early-season CC between 0.7 to 1.2%. Under high disease pressure, management programs using moderately resistant cultivars improved yields when compared to moderately susceptible cultivars. By contrast, minimum yield differences were detected between Rps1k andRps1c genotypes, except in one environment. While a weak to moderate correlation was observed between CC and incidence of P. sojae symptomatic plants, a moderate to strong association was found between CC and yield. Across multiple environments, PRE herbicides chlorimuron-ethyl, metribuzin, saflufenacil, sulfentrazone, and flumioxazin had no impact on seedling root rot (disease severity index; DSI) when compared to the non-treated control. Similarly, no significant differences between PRE herbicides were detected on plant population, plant height, and yield. Community composition depicting primary pathogenic genera Fusarium, Phytophthora, Pythium, and Rhizoctonia did not occur at random but rather varied across environments and DSI classes. In two of the three environments, Phytophthorastructured approximately 22% of primary pathogenic genera, whereas, Rhizoctoniarecovery was low (

Download or read book Identifying and Characterizing Fungal Pathogens Causing Seedling Diseases on Soybean Through a Multi state Survey written by Amanda Mandi Jo Warner and published by . This book was released on 2017 with total page 314 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Studies in the Management of Pythium Seed and Root Rot of Soybean written by Kelsey L. Scott and published by . This book was released on 2018 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt: In Ohio, soybean seedling damping-off and seed rot are problems routinely encountered soon after planting. Reduced tillage systems that lead to inoculum build-up combined with saturated soil conditions are ideal environments for seedling diseases, which cause large losses of soybean stand and thus yield. Prior Ohio field surveys identified multiple species of Pythium and Phytophthora that contribute to soybean seedling damping-off. Among the most common and aggressive species are Phytophthora sojae, Pythium irregulare, Pythium ultimum var. ultimum, and Pythium ultimum var. sporangiiferum. Fungicide seed treatment and host resistance are two management strategies that are used to minimize yield loss caused by these pathogens. Thus, the objectives of these studies were to: i) evaluate new active ingredients for efficacy in the lab and field, and ii) identify and characterize new sources of resistance towards the most common seedling pathogens. These are key strategies for the development of effective strategies for the management of soybean seedling disease. During 2014-2015, at two environments, ethaboxam seed treatments combined with metalaxyl on a susceptible cultivar significantly increased yield compared to other fungicide treatments containing metalaxyl or mefenoxam alone. Soybeans treated with ethaboxam plus metalaxyl had significantly higher plant populations when compared to the nontreated control at all four 2016 field locations, while one environment had significantly higher yield. In laboratory seed plate and greenhouse cup assays, ethaboxam plus metalaxyl in a commercial formulation provided equal or better protection against multiple species of Pythium when compared with other seed treatments that contained metalaxyl or mefenoxam only. These results indicate that ethaboxam with metalaxyl is effective at managing seed and rot root caused by the diverse species of Pythium and Phytophthora and provides another seed treatment fungicide available to producers which can be used in an integrated disease management program. The parents that were used to develop six nested association mapping (NAM) populations were previously identified as segregating for resistance towards Phytophthora sojae, Pythium irregulare, Pythium ultimum var. ultimum, and Pythium ultimum var. sporangiiferum. Following inoculation in a cup assay, the resistance was quantitatively inherited in each of the NAM populations towards the four seedling pathogens. In total, 33 QDRL from the six populations surpassed the genome-wide logarithm of odds (LOD) threshold and there was a large number of suggestive QDRL that surpassed the chromosomal LOD threshold. Of these 33 significant QDRL, 10 explained more than 15% of the phenotypic variation. Only four QDRL conferred resistance to more than one of the oomycete pathogens; one on chromosome 3, one on chromosome 17, and two located at separate locations on chromosome 13. This indicates that there may be multiple mechanisms for resistance to these root pathogens. Further analyses are needed to precisely map these QDRL so they may be selectively bred into highly resistant germplasm in order to manage seed and seedling damping-off. These NAM populations will serve as a rich resource for breeders to incorporate resistance into adapted soybean cultivars.