Monosporascus root rot/vine decline (MRR/VD), caused by Monosporascus cannonballus, is a serious disease of the major melon production areas of Texas, California, and Arizona. We have previously identified differing levels of tolerance in melon germplasm based on vine disease symptoms. This study was conducted to evaluate the yield response of commercial and experimental cantaloupe and honeydew hybrids subjected to MRR/VD. Thirty-nine and six cantaloupe and honeydew hybrids, respectively, were transplanted into a field highly infested with M. cannonballus in March 1995 in a randomized, complete block with 4 replications. The field was highly infested with Monosporascus cannonballus. `Caravelle' (very susceptible) and `Deltex' (tolerant) were included as control entries. Fruit were harvested at maturity and sized. Any fruit that did not mature completely due to vine death were counted as culls (unmarketable). Marketable yield of the cantaloupe entries ranged from 26.74% to 67.35%. The most tolerant hybrids were `SR103654', `Don Carlos', `Explorer', and `Ovation'. Marketable yield of the honeydews ranged from 8.43% to 41.46%, with `Morning Ice' and `Creme de Menthe' showing the most tolerance. The best performing hybrids were evaluated again the Fall 1995 and Spring 1996 seasons. In general, genotypes which matured later, and had a more dispersed fruit set, were more tolerant to MRR/VD. This supports previous data showing that high physiological stress (heavy, concentrated fruit load) leads to more severe and rapid vine collapse.
A disease of muskmelon (Cucumis melo L.) characterized by a vine decline and a cortical root rot was first observed in the Lower Rio Grande Valley of Texas in 1986. In 1990, isolations from diseased plants collected from four commercial production fields yielded the fungus Monosporascus cannonballus. Pathogenicity tests with eight isolates confirmed Koch's postulates; however, there were differences in aggressiveness observed among isolates. M. cannonballus is an ascomycete fungus that typically produces only one (rarely two), round, jet-black ascospore per ascus. There is no known asexual stage. Temperature optimum of one isolate was 35 C. The optimum pH for growth was 6-7, but it grew well up to pH 9. M. cannonballus was first reported on muskmelon in 1970 from Arizona and recently was found in Japan under glass house culture. The presence of this fungus in Texas marks only the third report of this species worldwide, although a similar species (M. eutypoides) is the cause of a collapse of melon plants in Israel.
.E. Macrì, C. Carlucci, A. Lops, R. Mucci, M. Raimondo, M.L. Frisullo, S. 2008 Fungi associated with root rot collapse of melon in Italy EPPO Bul. 38 147 154 Cohen, R. Elkind
caused by increased water stress as a result of heavy fruit load on grafted plants. Minuto et al. (2010) also reported sudden collapse and decreased fruit yield of melon plants grafted with hybrid squash rootstocks in Italy. ‘Fiola’ melon ( C. melo var
physiological collapse of melon plants under field conditions. Vigor of wild rootstocks can be increased by using interspecific hybrids, which have the additional advantage of combining resistances or other suitable traits from both parental lines. Although
isolated a specific pathogen known to contribute to sudden wilt either from melon plants or soils in our research plots. Although Martyn (2007) and Zitter (1995) have listed numerous pathogens implicated in reports of sudden wilt or late collapse
; Fita et al., 2009 ). MVD is a melon soilborne disease caused primarily (but not only) by the fungus M. cannonballus Pollack et Uecker, which rots the roots. Melon vine decline and/or collapse results from a damaged root that is unable to supply the
Melon production is severely constrained by several soil-borne disease pathogens. Of these pathogens, Didymella bryoniae (Auersw), Rehm that causes gummy stem blight (GSB) is one of the most destructive resulting in substantial economic losses
collapse. There are currently no commercial cucumber cultivars with resistance to this disease. Our prior screening of young fruit from 1076 accessions from the U.S. cucumber PI collection identified three PIs with potential resistance: PI 109483 and PI
fruit rot ( Roberts et al., 2001 ; Zitter et al., 1996 ). Crown rot appears at the soil line causing stems to turn dark brown, become water-soaked, and quickly collapse causing plant death. Foliar symptoms appear as rapidly expanding, water