Forty-two Rhizoctonia isolates were collected from rice, mung bean, and grasses from Laguna, Philippines. Sixteen isolates were binucleate Rhizoctonia (BNR), while 26 were multinucleate Rhizoctonia (MNR). BNR isolates produced white to brown, small sclerotia (<1.0 mm) except for mung bean isolates. Twenty MNR isolates produced big (>1.0 mm), light to dark brown sclerotia, three produced salmon-colored masses in the medium, and three did not produce sclerotia. Twenty-three MNR isolates were identified as R. solani AG1-IA using specific primers. Deduced Internal Transcribed Spacer (ITS) sequences of BNR isolates D1FL, NVL, and ScNL shared 100, 97, and 100% identity with R. oryzae-sativae, respectively, while MNR isolates BMgL, IbMgL, and MaSL that produced salmon-colored masses shared 100, 90, and 100% identity with R. oryzae, respectively. Preliminary analysis of the DNA fingerprint patterns generated by repetitive-element PCR (rep-PCR) clustered the 42 isolates into three: R. solani, R. oryzae-sativae, and R. oryzae, together with Ceratobasidium sp. R. solani isolates were pathogenic on rice (TN1), barnyard grass, mungbean (Pagasa 3), and tomato (Athena), while R. oryzae and R. oryzae-sativae isolates were only pathogenic on rice, Echinochloa crus-galli, and tomato. R. solani and R. oryzae were found to be more virulent than R. oryzae-sativae.
Keywords: Rhizoctonia; molecular markers; phenotypic markers; rice.