Submitted to: Subtropical Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/19/1999
Publication Date: N/A
Interpretive Summary: Muskmelon is an important horticultural crops in the U S comprising more than 40,000 hectares at a value of approximately $125 million. Almost 90% of the production is in Arizona, California, and Texas. The soilborne pathogen Monosporascus cannonballus is the greatest yield-limiting factor to muskmelon production in these states causing severe losses in some years. Currently, there are no effective control measures for Monosporascus root rot/vine decline available and genetic resistance is inadequate in commercial cultivars. Biological control of Monosporascus root rot/vine decline of muskmelon and watermelon provides a promising strategy to explore since biocontrol agents can colonize plant root systems and interact with the pathogens to suppress root diseases. Based on this concept, we attempted to determine the potential of a biocontrol agent, Trichoderma virens, for the control of Monosporascus root rot/vine decline of muskmelon plants. Our experimental results indicated that T. virens ha both antibiotic and parasitic activity against M. cannonballus. Under greenhouse conditions, T. virens colonized muskmelon seedling root system, and reduced colonization of muskmelon roots by M. cannonballus, and significantly suppressed disease severity after a seed treatment with T. virens preparations. This is the first time that T. virens is demonstrated to have a potential for the control of root rot/vine decline of muskmelon. Our experimental results appear to provide a new strategy to implement into the integrated management of root rot/vine decline diseases of cucurbits.
Technical Abstract: Root rot/vine decline disease of muskmelon, incited by Monosporascus cannonballus, causes severe economic losses in many hot semi-arid production areas. No effective control measures for Monosporascus root rot/vine decline are presently available and genetic resistance is not adequate in commercial cultivars. We have attempted to determine the potential for biocontrol of root rot/vine decline diseases on muskmelon using Trichoderma virens. T. virens exhibited in vitro antibiotic activity by inhibiting mycelial growth of M. cannonballus and other vine decline pathgens such as Didymella bryoniae, Macrophomina phaseolina and Phomopsis cucurbitae. A gliotoxin producing strain of T. virens (TV-6) demonstrated much stronger inhibition of the fungal pathogens when compared with T. virens strain TV-4 which does not produce gliotoxin. In addition to antibiotic activity, T. virens demonstrated parasitism of M. cannonballus mycelium. Under greenhouse conditions, T. virens colonized the root systems of muskmelon plants, significantly reduced the colonization by M. cannonballus of muskmelon seedling roots, and suppressed severity of seedling disease using a seed treatment. T. virens strains TV-4 and TV-6 performed best in suppression of M. cannonballus root rot among the T. virens strains and isolates tested. Preliminary experimental data suggest that strains of the biocontrol agent T. virens may have potential as an additional strategy for the integrated management of root rot/vine decline diseases of muskmelon.