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

Rhizoctonia-diseased specimens were collected from various host species gro wing in or near maize fields in different geographic regions of the Philipp ines. A greater range of host species, with varying types of disease sympto ms, was found in Mindanao than in Luzon. Fifty-two isolates belonged to ana stomosis group AG1-IA and caused banded leaf and sheath blight in maize (Ze a mays), but they showed considerable variation in virulence. The most and least virulent isolates recovered from maize were both collected from Minda nao. Isolates from necrotic spots/foliar blight of durian and coffee, which were collected from the same region, showed the lowest lesion heights. UPG MA-SAHN clustering analysis from RAPD fingerprint data of 30 haplotypes of R. solani AG1-IA isolates from the Philippines and Japan resolved seven gro ups of AG1-IA at the 75% similarity level. Variation among isolates from up land crops seemed to be partially correlated with geographical origin and v irulence. 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 diff erentiated from subgroups AG1-IB and AG1-IC using the endonucleases EcoRI, MboI and HinfI.