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Title: Charcoal Rot Disease Assessment of Soybean Genotypes and Prelimary Genetic Analysis

item Mengistu, Alemu
item Smith, James - Rusty
item Ray, Jeffery - Jeff
item Paris, Robert

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/15/2006
Publication Date: 6/20/2006
Citation: Mengistu, A., Smith, J.R., Ray, J.D., Paris, R. 2006. Charcoal Rot Disease Assessment of Soybean Genotypes and Prelimary Genetic Analysis. Meeting Proceedings. VII World Soybean Research Conference. Foz do 1guassu, PR, Brazil. # 228, p 237.

Interpretive Summary:

Technical Abstract: Charcoal rot [Macrophomina phaseolina (Tassi) Goid] of soybean [Glycine max (L.) Merr.] is a disease of economic importance in the United States that causes significant yield losses. In 2002 (30), 2003 (30), 2004 (44) and 2005 (81) a total of 185 soybean genotypes in maturity groups III, IV and V were evaluated using five methods of disease assessments: 1. Internal stem discoloration (PSHD), 2. Colony forming units (CFU), 3. Foliar symptoms, 4. Area under disease progress curve for foliar symptoms (AUDPC) and 5. Severity based on the intensity of internal stem discoloration. Linear regression of disease assessment as a function of the intensity of internal stem severity was significantly correlated (r2=0.56, P less than or equal to 0.0001) with CFU. However, when all disease measurements were combined the regression trend improved significantly (r2=0.85, P less than or equal to 0.0001). Genotypes that ranked high for resistance as measured by CFU also ranked high using combined measurements of severity, PHSD, foliar and AUDPC. Such methodology is more feasable for measurement of resistance than quantification with CFU. Using this protocol, ‘DT97-4290’ (a maturity group IV breeding line) was identified as having moderate resistance to charcoal rot. This line was released in December 2004 because of its high yield potential, charcoal rot resistance, and resistance to southern stem canker (Diaporthe phaseolorum var. meridionalis). Using DT97-4290 as the resistant parent, populations have been created to evaluate inheritance and identify molecular markers. To date, the parents, F1s, and F2s of 6 populations as well as F3 families for 1 population have been phenotyped.