Submitted to: Open Mycology Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/26/2009
Publication Date: 4/20/2009
Publication URL: http://hdl.handle.net/10113/28645
Citation: Cluck, T.W., Biles, C.L., Dugan, M., Jackson, T., Carson, K., Armengol, J., Garcia-Jimenez, J., Bruton, B.D. 2009. Association of dsRNA to down-regulation of perithecial synthesis in Monosporascus cannonballus. Open Mycology Journal. 3:9-19. Interpretive Summary: In the last twenty-five years, soilborne diseases have become the yield-limiting factor in many cucurbit production areas around the world. Monosporascus cannonballus is one of the most important soilborne pathogens causing vine decline of muskmelon and watermelon. Currently there are no resistant cultivars to M. cannonballus and effective soil fumigants are restricted or banned in many melon producing countries. The purpose of this study was to ascertain the frequency of dsRNA (hypovirus) in Spanish isolates of M. cannonballus and to compare the presence or absence of dsRNA with production of perithecia and pigment formation. The variation in dsRNA banding patterns was used to group the Spanish M. cannonballus isolates into statistically independent dendrogram clusters. Results demonstrated that certain dsRNA patterns were associated with reduced perithecial formation. Insertion of the M. cannonballus hypovirus sequences into the plant genome holds the potential for a new resistance mechanism against this plant pathogen by inhibiting reproduction of the fungus following infection of the plant.
Technical Abstract: 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. Isolates were grouped based on dsRNA fragment sizes using cluster analysis and Elucidean 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. Additional research is needed to elucidate the mechanisms of regulation by the dsRNA of M. cannonballus.