Assessing the suitability of morphological and phenotypical traits to screen sesame accessions for resistance to Fusarium wilt and charcoal rot diseases

Since sesame accessions differ significantly in many morphological and phenotypical traits, some of these traits could be suitable for direct selection for resistance to Fusarium wilt and charcoal rot diseases. Forty-eight sesame accessions that originated from different countries were screened for their reaction to infection by Fusarium oxysporum f.sp. sesami (FOS) and Macrophomina phaseolina (MPH), the Fusarium wilt and charcoal rot pathogens, respectively, in 2005 and 2006. The level of infection and seed yield were measured. Number of branches and days to maturity as morphological traits and seed color as phenotypical trait, which represent some of the diversity among the accessions, were tested for possible correlation with infection percentage. We found that 57, 67 and 67% in 2005, and 77, 77 and 62% in 2006 of the accessions resistant to FOS, and 68, 77 and 64% in 2005, and 80, 76 and 60% in 2006 of the accessions resistant to MPH had a medium branch number, medium maturity and creamy seed colour. According to the analysis of regression, branch number and seed colour were significantly correlated with infection percentages by FOS and/or MPH. Therefore, these traits may be used for direct selection of sesame accessions that are resistant to Fusarium wilt and charcoal rot disease. However, no significant correlations were found between days to maturity and infection percentage by both fungi. Linear regression between infection percentage and three groups of branch number and seed colour indicated that the accessions with medium branch number and creamy or white seed colour were the only covariate which significantly correlated with the infection percentage by FOS and/or MPH.