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Title: Comparsion of Disease Assessment of Soybean Genotypes in the Presence of Charcoal Rot

Author
item Mengistu, Alemu
item PARIS, ROBERT - ASSOC FOR CHESTNUT FOUND
item Smith, James - Rusty
item Ray, Jeffery - Jeff

Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: 3/15/2006
Publication Date: 3/17/2006
Citation: Mengistu, A., Paris, R., Smith, J.R., Ray, J.D. 2006. Comparsion of Disease Assessment of Soybean Genotypes in the Presence of Charcoal Rot. [Meeting Abstract]. 93:S61

Interpretive Summary:

Technical Abstract: Charcoal rot [Macrophomina phaseolina (Tassi) Goid] of soybean [Glycine max (L.) Merr.] is a disease of economic significance in the United States causing significant yield losses. Twenty four soybean genotypes in maturity groups 3, 4 and 5 were evaluated in 2002 and 2003 using five methods of disease assessments: 1. Internal stem discoloration (PSHD), 2. Colony forming units (CFU), 3. Foliar symptoms taken at the R7 growth stage, 4. Area under disease progress curve for foliar symptoms (AUDPC) taken three or four times during the season, and 5. Severity based on the intensity of internal stem discoloration. Linear regression of disease assessment as a function of internal stem severity was significantly correlated (r2=0.559, P=0.0001) with the CFU. However, when all disease measurements were combined the regression trend improved significantly (r2=0.85, P=0.0001). Genotypes that ranked high for resistance as measured by CFU also ranked high using measurements of severity, PSHD, foliar and AUDPC and their combinations. Such methodology for measurement of resistance is less time consuming and adaptable than quantification with CFU. Based on the five disease assessments, five breeding lines DT 99-17554, DT 99-17483, DT 99-16864, DT 99-7553 and DT 97-4290 were rated as moderately resistant to M. phaseolina. DT 97-4290 was released as a germplasm in 2004 because of its resistance to charcoal rot and high yield potential.