Investigation of pathogenicity of four Macrophomina phaseolina isolates on four safflower genotypes

Macrophomina phaseolina attacks many crop species including safflower and it causes charcoal rot. To investigate the pathogenicity of four M. phaseolina isolates (M0, M2, M5 and M6) on four safflower genotypes (Acetria, LRV5151, Arak 2811 and 34074), this study was performed at the Agricultural Sciences and Natural Resources University of Gorgan. The length of spots caused by fungi isolates inoculated in the lower part of plant stem was measured. This experiment was performed in an unbalanced completely randomized design under field conditions. The results of analysis of variance showed a significant difference between the isolates at 1% probability level. The interaction of genotype × isolates was significant at the 1% level. In this study, isolate of M2 with a maximum length of spots on all four safflower genotypes was identified as the most virulent isolate and M0 with the least length of spot was the least virulent isolate. Among the genotypes, genotype Acetria to two isolates of M0 and M6, genotype LRV5151 to two isolates of M0 and M5 and genotype 34074 to two isolates of M5 and M6 showed more resistance. None of the genotypes was resistant to isolate M2 and all genotypes were susceptible to this isolate.