Genotypic differences in yield loss of irrigated soybean attributable to charcoal rot

Authors: Smith, James - Rusty; Ray, Jeffery - Jeff; Mengistu, Alemu

Submitted to: Journal of Crop Improvement
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/22/2018
Publication Date: 11/26/2018
Publication URL: https://handle.nal.usda.gov/10113/6239432
Citation: Smith, J.R., Ray, J.D., Mengistu, A. 2018. Genotypic differences in yield loss of irrigated soybean attributable to charcoal rot. Journal of Crop Improvement. 32(6):781-800. https://doi.org/10.1080/15427528.2018.1516262.
DOI: https://doi.org/10.1080/15427528.2018.1516262

Interpretive Summary: Charcoal rot is a fungal disease of soybean that occurs wherever soybeans are grown. Yield losses of soybean are generally more severe when drought and charcoal rot occur together. The purpose of this research was to determine the effect of charcoal rot on the yield loss of six different diseased soybean lines grown in irrigated plots. The plots were irrigated throughout the growing season to eliminate drought as a potential cause of yield loss. The research was conducted at Stoneville, MS in 2011, 2012, and 2013. Results indicated that charcoal rot caused yield loss for one line. For that line, as the level of charcoal rot on stems and roots increased, the amount of seed produced decreased in two out of three years (2011 and 2013). Interestingly, none of the other five soybean lines showed any relationship between charcoal rot and seed yield. For these lines, as the level of charcoal rot increased on the stems and roots, there was no corresponding decrease or increase of seed produced from those plants. Yet, all six soybean lines had the disease. This is the first study to demonstrate that not all susceptible soybean lines lose seed yield from charcoal rot when they have the disease. The genetics of the soybean line, the level of disease, and the environment are all important in determining yield loss. Knowledge gained from this study will enable soybean breeders to develop new varieties that better resist yield losses due to charcoal rot, which will then allow producers to reduce yield loss. Additionally, agronomists and crop production specialists may use the information from this study to conduct additional experiments utilizing irrigation to manage yield loss. Finally, geneticists may utilize the lines in this study to construct families for studying the inheritance of yield loss due to charcoal rot.

Technical Abstract: Charcoal rot, caused by the fungus Macrophomina phaseolina (Tassi) Goid., is a disease of soybean that causes yield loss worldwide. The purpose of this research was to determine the effect of charcoal rot on the yield loss of six individual soybean genotypes grown in infested irrigated plots. Overall, colony forming unit (CFU) levels were low (= 5,500). Even so, regression analysis indicated a significant (P = 0.05) negative linear relationship of CFUs with seed yield for one genotype in two out of three years (2011 r2 = 0.43, P = 0.0403; 2013 r2 = 0.71, P =0.0023) at levels of CFUs that ranged from zero to 1,300. At low CFU levels, none of the other five genotypes showed a significant (P = 0.05) linear relationship. Hence, not all genotypes that were colonized by M. phaseolina lost seed yield. These results indicate that yield loss may be dependent on both genotype and environment.