Research highlights on the evaluation of soybean genotypes for responses to pathogens in the Southern States of the USA

Authors: Li, Shuxian

Submitted to: International Congress of Plant Pathology Abstracts and Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 5/26/2023
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Soybean is one of the most economically important legume crops grown in the world due to its unique seed composition and broad applications in the food and fuel industries. It provides plant-based protein and oil for animal and human nutrition. The global demand for soybean has increased dramatically. However, various soybean diseases cause substantial monetary losses every year by reducing seed yield and quality. Analyses of host plant responses to pathogens is an important step towards breeding improved disease resistant soybeans. Phenotyping soybean genotypes with known and unknow Rpp resistance genes for their responses to the causal agent Phakopsora pachyrhizi was carried out using both seedling and detached leaf assays. PI 200492 (Rpp1) had an immune reaction when tested with isolate MS06-1b (collected from Mississippi in 2006) and RB lesion reactions to FL08, FLQ11, FLQ12 (collected from Florida in 2008, 2011 and 2012, respectively), and LA15 (collected from Louisiana in 2015), whereas PI 230970 (Rpp2), PI 462312 (Rpp3), PI 459025B (Rpp4), PI 567102B (Rpp6) and PI 605823 (Rpp7) had resistant reactions with RB lesions to isolate MS06-1b. Williams 82 and PI 200526 (Rpp5) had susceptible TAN reactions with the greatest severity and sporulation ratings to isolate MS06-1b. Screening hundreds of soybean germplasm and breeding lines for their responses to Diaporthe longicolla, a causal agent of Phomopsis seed decay (PSD), in Southern U.S. states has identified new sources of resistance. Although PSD is a soybean seed disease, a cut-seedling inoculation technique was developed to rapidly evaluate soybeans for reaction to D. longicolla and identify PSD resistant genotypes, without waiting a whole growing season. Data from the seedling technique are comparable to those obtained from field tests. Additionally, concerns about the environmental effects and uneven distribution of D. longicolla in the field were managed. Further, nine soybean accessions having resistant reactions to Cercospora spp., causing purple seed stain (PSS) of soybean, were previously reported as resistant to PSD. These could be useful in breeding programs to develop soybean cultivars with improved resistance to both seed diseases. A brief overview of research on soybean responses to these and other important soybean pathogens will be presented.