Assessing the Suitability of Morphological and Phenological Traits to Screen Sesame Genotypes for Fusarium Wilt and Charcoal Rot Disease Resistance

Since sesame genotypes differ significantly in many morphological and phenological traits, some of these traits could be suitable for direct selection among the sesame genotypes for Fusarium wilt and charcoal rot disease resistance. Forty-eight sesame genotypes that originated from different geographical regions were screened for their response to infection by Fusarium oxysporum f. sp. sesami (FOS) and Macrophomina phaseolina (MPH), the Fusarium wilt and charcoal rot pathogens in 2005 and 2006 seasons, respectively. The seed yield and infection percentage by Fusarium wilt and charcoal rot pathogens were determined. Branch number and days to maturity as morphological traits and seed colour as phenological trait which represented the proposal for diversity among sesame genotypes were correlated with infection percentage and were used to examine the performance of these traits as screening criteria for Fusarium wilt and charcoal rot disease resistance. Our results showed that 57, 67 and 67% in 2005 and 77, 77 and 62% in 2006 of resistant genotypes for FOS, and 68, 77 and 64% in 2005 and 80, 76 and 60% in 2006 of resistant genotypes for MPH had a medium branch number, and were of medium maturity and having creamy seed colour, respectively. 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 as indices for direct selection for resistance of sesame genotypes to Fusarium wilt and charcoal rot disease. However, no significant correlation was 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 sesame genotypes had medium branch number and having creamy or white seed colour were the only covariant which significantly correlated with the infection percentage by FOS and/or MPH.