Phenotypic variation of Rhizoctonia oryzae in sheath disease of rice in Myanmar

Similarity in the cultural characteristics among closely related species of Rhizoctonia creates confusion and uncertainity in diagnosis. The present research was conducted to study the existence of phenotypic groups among isolates of R. oryzae in Myanmar. It was aimed to study the variation in phenotypic and molecular profiles among some isolates of R. oryzae and R. zeae. We found the occurrence of two distinct phenotypic groups of R. oryzae and a group of R. zeae. Ribosomal DNA-ITS sequencing was conducted and the resulting dendrogram agreed with those of the morphological grouping. A genetic distance of 0.064-0.072 wts was found between the R. oryzae and R. zeae groups. A pairwise distance of 0.014 and 0.022 was found between the RO1 and RO2 groups of R. oryzae. Our research revealed the existence of two distinct phenotypes in the isolates of R. oryzae collected from rice sheath in Myanmar and their differentiating features with R. zeae.