Charcoal rot severity and soybean yield responses to planting date, irrigation, and genotypes

Authors: Mengistu, Alemu; KELLY, HEATHER - University Of Tennessee; Read, Quentin; Ray, Jeffery - Jeff; Bellaloui, Nacer; Schumacher, Lesley

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/1/2022
Publication Date: 2/16/2023
Citation: Mengistu, A., Kelly, H.M., Read, Q.D., Ray, J.D., Bellaloui, N., Schumacher, L.A. 2023. Charcoal rot severity and soybean yield responses to planting date, irrigation, and genotypes. Plant Disease. https://doi.org/10.1094/PDIS-06-22-1329-RE.
DOI: https://doi.org/10.1094/PDIS-06-22-1329-RE

Interpretive Summary: Soybean production is influenced by planting date but its impact on disease severity and yield in fields infested with charcoal rot fungus under varying environment is unknown. Our research detected that disease severity in May planting date was lower compared to April and June. Yield in April planting date was lower than that of May and June in both irrigated and non-irrigated environments. Soybean lines interacted with planting date differently, however, selected moderately resistant lines showed the greatest yields in early May to early June. Interestingly, yield of susceptible lines increased with each subsequent planting date. The results of this research fill the knowledge gaps in the current soybean production system that may need to be considered and will be incorporated into the current farming practices that will ultimately benefit midsouth soybean growers.

Technical Abstract: Soybean (Glycine max (L.) Merr.) production is influenced by planting date (PD) but its impact on yield in fields infested with Macrophomina phaseolina (Tassi) Goid. is unknown. A three-year study was conducted in M. phaseolina infested fields to assess the effects of planting date (PD) on disease severity and yield using eight genotypes, four of which are reported to be susceptible to charcoal rot (SCR) and four reported with moderate resistance (MR) to charcoal rot (CR). The genotypes were planted in early April, early May, and early June under irrigated and non-irrigated conditions. The mean Area Under the Disease Progress Curve (AUDPC) was significantly lower for May PD compared to April and June PDs, but April and June PDs did not significantly differ from each other compared to April and June PDs. Correspondingly, yield in April PD was significantly lower than that of May and June PD. Interestingly, yield of SCR genotypes increased significantly with each subsequent PD while yield of MR genotypes remained high across all three PDs. Even though there was no significant main effect of irrigation on AUDPC, May PD had a significantly lower AUDPC than April and June PD only in an irrigated environment. Additionally, yield in May and June remained significantly higher than April PD in both irrigated and non-irrigated environments. The interaction of genotypes by PD on yield revealed the greatest difference between genotypes in April and May PDs, where the MR genotypes DT97-4290 and DS-880 had the greatest yields. While May PD had a decreased AUDPC and an increased yield across genotypes, this research further affirms that planting selected MR genotypes in early May to early June PD increases yield in M. phaseolina infested environments.