Association of dsRNA to Down-Regulation of Perithecial Synthesis in Monosporascus cannonballus

Monosporascus cannonballus is a soilborne fungal pathogen that causes vine-decline of muskmelon which results in reduced yield in many melon growing areas around the world. M. cannonballus isolates were collected from different provinces in Spain and experiments conducted to determine pigmentation, perithecial formation, and the presence of cellular dsRNA. Thirty-one isolates were grouped based on dsRNA fragment sizes using cluster analysis and Euclidean distances. Three distinct dsRNA groupings were observed. Group 2 isolates containing 2, 3, and 3.5 kb dsRNA appeared to exhibit a decrease in perithecia production compared to the other groups. Group 1 isolates exhibited yellow pigmentation only, while Group 3 isolates expressed grey (wild-type) and yellow (degenerate) pigmentation. Isolates that did not contain dsRNA (Group 4) exhibited wild-type pigmentation. Down-regulation and variation in phenotype are hypothesized to be due to dsRNA/iRNA interactions with the fungal transcription mechanisms. Future research will focus on elucidating the mechanisms of regulation by the dsRNA of M. cannonballus.