Double-stranded RNAs (dsRNAs) were detected in 7 of 96 isolates (7%) of Trichoderma spp. isolated from 13 provinces of Thailand. The dsRNA-containing isolates included Trichoderma sp. Cbi3.1.1 T. harzianum Cbi3.2.2 T. reesii Cbi3.3.1 Trichoderma sp. Cpn1.1.1 Trichoderma sp. Pbn1.1.5 T. virens Plk1.1.9 and Trichoderma sp. Ubn1.1.3. The number of dsRNA fragments in each fungal isolate ranged from 1 to 10 and their size ranged from approximately 1.25 to 21.9 kb. Complementary DNAs synthesized from 3 dsRNA fragments of T. reesii Cbi3.3.1 were cloned and sequenced. Partial amino acid sequences translated from the cDNA clones, c88, c101 and c171, were similar to putative RNA dependent RNA polymerases and putative capsid proteins of viruses in the genus Partitivirus. Results of phylogenetic analyses supported the close relationship between dsRNA from T. reesii Cbi3.3.1 and partitiviruses. When growth and endoglucanase production were compared between the single-cell colonies with and without dsRNA, the difference in growth rate was detected on Corn meal dextrose agar medium at 30°C and 40°C and higher sporulation in dsRNA-free colonies was observed in 14 day-old cultures. Higher protein content was also detected in the crude enzyme produced by dsRNA-free colonies. However, no significant difference was found in endoglucanase production.
