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

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. 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.

Advances in the Biology and Management of Monosporascus Vine Decline and Wilt of Melons and Other Cucurbits

“…An interesting note is that these pigments developed in a wildtype isolate, presumably without dsRNA, after long-term storage. There is no mention of dsRNAs in this isolate; however, the majority of isolates collected from infected melon plants harbor multiple dsRNAs Cluck et al 2009). It is possible that this isolate contained dsRNA, perhaps in a latent state, and phenotypic aberrations did not occur until some time later after dormant storage.…”

“…The association of specific dsRNAs in M. cannonballus with a respective phenotype has been difficult to determine, although it is thought that dsRNA fragments in the size range of 2.5-3.5 kb are most likely responsible for the majority of the phenotypic changes, including the change to hypovirulence Park 1996;Park et al 1996b;Batten et al 2000a). Cluck et al (2009) examined 33 isolates of M. cannonballus collected from eastern Spain; all but three contained multiple dsRNAs, ranging in size from 1.5-9 kb. As many as two to nine different dsRNA fragment sizes were detected within a given isolate.…”

Effect of dsRNA on growth rate and reproductive potential of Monosporascus cannonballus

“…Matsum. & Nakai) crops (Martyn & Miller 1996;Bruton 1998;Cluck et al 2009). Since the mid-1980s, this disease has been prevalent in cucurbit-production areas located in hot semi-arid to arid regions, as well as subtropical environments (Martyn & Miller 1996).…”

“…Symptoms of the disease include the yellowing and death of the crown leaves that gradually radiate out and kill the vine as the fruit approach maturity (Martyn & Miller 1996;Cluck et al 2009). Monosporascus cannonballus produces ascospores in perithecia formed on affected roots at the end of the cropping season (Martyn & Miller 1996).…”

Fitness components of Monosporascus cannonballus isolates from northeastern Brazilian melon fields

“…Colonies were further incubated until 45 days for perithecia formation and quantification as described by Cluck et al (2009). Four plugs (12 mm diameter) were randomly selected and removed from each colony, and each plug was considered a replicate (16 plugs per isolate).…”