Abstract

Charcoal rot that is caused by Macrophomina phaseolina, the most damaging disease in sesame in China. Variations in the 35 isolates of M. phaseolina collected from the main sesame producing regions in central China comprising of Hubei, Henan, Anhui, Jiangxi province were studied based on morphology, pathogenicity and amplified fragment length polymorphism (AFLP). The results showed that the morphological characteristics, including density of aerial mycelia, sclerotia quantity, sclerotium size and growth speed of colony, had rich variations. The pathogenicity index of these isolates ranged from 0.03 to 4.64 with an average of 2.10. Four isolates (17, 21, 28 and 35) with pathogenicity index more than 4.0 from the locations alongside Yangtze River were found here. AFLP analysis indicated that the paired genetic similarity coefficients of these isolates ranged from 0.65 to 0.97 with an average of 0.83. These isolates could be divided into seven genotypic groups based on unweighted pair group method with arithmetic mean (UPGMA) dendrogram. However, no clear relationships among the groups, geographic regions and PI were found. These results may be helpful to understanding the population structure of the fungus and contribute to the control of sesame charcoal rot in China.

Key words: Macrophomina phaseolina, pathogenicity, charcoal rot, sesame, amplified fragment length polymorphism (AFLP).