Characterization by conventional techniques and PCR of <i>Rhizoctonia solani</i> isolates causing banded leaf sheath blight in maize

Abstract

Rhizoctonia ‐diseased specimens were collected from various host species growing in or near maize fields in different geographic regions of the Philippines. A greater range of host species, with varying types of disease symptoms, was found in Mindanao than in Luzon. Fifty‐two isolates belonged to anastomosis group AG1‐IA and caused banded leaf and sheath blight in maize ( Zea mays ), but they showed considerable variation in virulence. The most and least virulent isolates recovered from maize were both collected from Mindanao. Isolates from necrotic spots/foliar blight of durian and coffee, which were collected from the same region, showed the lowest lesion heights. UPGMA‐SAHN clustering analysis from RAPD fingerprint data of 30 haplotypes of R. solani AG1‐IA isolates from the Philippines and Japan resolved seven groups of AG1‐IA at the 75% similarity level. Variation among isolates from upland crops seemed to be partially correlated with geographical origin and virulence. In the case of paddy rice isolates from Japan and the Philippines, some were closely related, with over 75% similarity, suggesting a common origin. In PCR‐RFLP analysis of the rDNA internal transcribed spacer region, no polymorphism was observed among the AG1‐IA isolates but they were differentiated from subgroups AG1‐IB and AG1‐IC using the endonucleases Eco RI, Mbo I and Hin fI.