Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: October 1, 2003
Publication Date: November 1, 2003
Citation: Mengistu, A., Paris, R.L. 2003. Comparison of disease assessments of soybean genotypes in the presence of charcoal rot. Phytopathology. 93:561 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. In 2002, 26 soybean genotypes in maturity groups 4 and 5 were evaluated using five methods of disease assessments: 1. Internal stem discoloration (PSHD), 2. Colony forming units (CFU), 3. Severity of foliar symptoms, 4. Area under disease progress curve (AUDPC) and 5. Severity based on the intensity of internal stem discoloration. Disease assessment based on the internal stem severity was significantly correlated (r<sub>2</sub>=0.559) with the CFU. However, when all disease measurements were combined the correlation improved significantly (r<sub>2</sub>=0.85). Genotypes that ranked high for resistance as measured by CFU also ranked high using combined measurements of severity, PHSD, foliar and AUDPC. Such methodology for measurement of resistance is more adaptable than quantification with CFU. Additional studies are planned to confirm these findings and also develop laboratory or greenhouse assays to assess varietal reaction to charcoal rot.