Molecular, physiological and infection behaviour studies of Rhizoctonia solani causing the Rice Sheath Blight disease

Abstract

Rhizoctonia solani is the causal agent of rice sheath blight, which is one of the most serious diseases of rice worldwide. In this study, seventeen Egyptian isolates of sheath blight pathogen, R. solani AG1 IA, were identified using morphological and molecular characterization by the internal transcribed spacer (ITS) sequences. Extracellular enzymes were assessed in in vitro and in infected rice samples. Also, pathogenicity tests for all isolates were done on two rice cultivars under greenhouse conditions. Growth behavior by RS13 isolate was studied using two rice cultivar Sakha 101 (Japonica type) and Egyptian Yasmine (Indica type). The obtained results exhibited a wide range of variability in the morphological and virulence characteristics of isolates. Two isolates RS10 and RS13 (AB5) were sequenced and found aligned with Egyptian and Chinese isolates. RS13 and RS10 isolates exhibit the highest production of cellulase, pectinase and amylase enzymes in plate culture (in vitro). While, on the plant sample tissue cellulase and pectin methylesterase (PME) activity enzymes are relating to development of rice sheath blight disease. Under the artificial condition, SK 101 rice proved the most susceptible to infection with sheath blight pathogen compare with E. Yasmine. The hyphae growth on SK101 cultivar was more than in the E. Yasmine cultivar. Furthermore, we examined the morphological developments of hyphae and sclerotial on both cultivars using light and scanning electron microscopy (SEM). It was observed that the fungal pathogen could intercept host surface structures for improving cell penetration and anchorage.