Identification and pathogenicity of Macrophomina species in sesame fields from Iran

Abstract

Sesame (Sesamum indicum L.) is one of the most important oilseed crops in tropical and subtropical regions of the world. Iran is the 16^th sesame producer in the world. Despite long cultivation of sesame and the presence of charcoal rot disease for decades in Iran, comprehensive studies has not been performed on the causal agents of charcoal rot and disease management. The purpose of this research was to identify Macrophomina species causing charcoal rot in major sesame -growing areas of Iran. Samples were collected from sesame plants and two dominant weeds of sesame fields, Amaranthus retroflexus and Convolvolus arvensis, with symptoms of charcoal rot from five provinces of Iran: Bushehr, Fars, Khuzestan, Hormozgan, and Kohgiluyeh & Boyer-Ahmad. All isolates were identified as M. phaseolina based on morphological characters. Molecular identification was performed by phylogenetic analysis of ITS-rDNA and tef1-α regions. All isolates from sesame were confirmed as M. phaseolina while isolates from A. retroflexus and C. arvensis were identified as M. euphorbiicola. The reaction (resistant/susceptible) of eight commercially important sesame cultivars to M. phaseolina and M. euphorbiicola was evaluated under greenhouse conditions. All M. phaseolina isolates caused charcoal rot on root, crown, and stem tissues while M. euphorbiicola-inoculated sesame cultivar were asymptomatic. In this research, we concluded that Behbahan and Dashtestan cultivars could be suggested as the preferable and superior cultivars for cultivation in areas under infestation by M. phaseolina in the South and Southwest Iran.