Comparative Epidemiology of Monosporascus Root Rot and Vine Decline in Muskmelon, Watermelon, and Grafted Watermelon Crops

Abstract

Disease progression and soil population dynamics of Monosporascus cannonballus ascospores were studied and compared through the entire growing season in muskmelon, watermelon, and watermelon grafted onto Cucurbita rootstock crops. In muskmelon and watermelon, there was a decrease of ascospore counts in soil from transplanting until first symptoms of vine decline were observed. This decrease probably was related to ascospore germination and subsequent root infection. Later, there was a remarkable increase of ascospore counts in a parallel way to the quick development of vine decline symptoms, which lead to plant death. In these crops, root colonization adjusted to first-order linear equations and vine decline progression best correlated with exponential and logistic models. In contrast, there were no symptoms of vine decline on grafted watermelon. Furthermore, the isolation of M. cannonballus from Cucurbita roots was considerably lower, perithecia were never observed, and ascospore soil populations remained stable. These results suggest that disease control by grafting onto genus Cucurbita seems to be related primarily by the increased resistance of its root system to infection by M. canonballus, and provide further evidence of the use of grafting as a disease management measure for this disease.

Germination ofMonosporascus cannonballusascospores in the rhizosphere: a host-specific response

“…As previously mentioned, no ascospores germinated in the rhizosphere of C. maxima and cultivars of this cucurbit are currently employed as M. cannonballus-resistant rootstocks for grafting of susceptible melons scions (Edelstein et al, 1999;Cohen et al, 2000Cohen et al, , 2005Beltrán et al, 2008). Lack of ascospore germination, as documented in this study, provides direct evidence in support of the conclusion of Beltrán et al (2008) that resistance of squash rootstock resides in the 'lack of recognition between the host and the pathogen'. Further, our experiments involving co-cultivation of 'Brava' and 'Caravelle' in the same soil assay tube demonstrated that exudates from 'Brava' did not inhibit ascospore germination and that ascospores stimulated to germinate by 'Caravelle' roots did not attach to 'Brava' roots.…”

Colonisation and histological changes in muskmelon and autumn squash tissues infected by Acremonium cucurbitacearum or Monosporascus cannonballus

“…Owing to its tolerance, autumn squash is routinely used as a rootstock for both muskmelon and watermelon in order to control soil-borne diseases, such as Fusarium wilt (Miguel et al 2004), Acremonium collapse (in watermelon; Armengol et al 1998) and Monosporascus wilt (in muskmelon; Cohen et al 2005;in watermelon;Beltrán et al 2008). Furthermore, research indicates that the symptoms caused by both fungi are more severe in melons and watermelons than in squash (Aegerter et al 2000).…”

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

“…Tests conducted in Spain with watermelon grafted onto Cucurbita rootstock showed no signs of disease. M. cannonballus was isolated from the roots but at lower frequencies than in Texas (Mertely et al 1993a) and perithecia were not observed (Beltr an et al 2008). In addition, the population of ascospores in the soil remained stable during the season.…”

“…Interspecific grafting of melons with other cucurbits has the potential to reduce damage caused by M. cannonballus and other soilborne pathogens (Cohen et al 2007;Davis et al 2008). Most cucurbits other than melon and watermelon reportedly do not experience much disease in the field due to M. cannonballus, in spite of the fact that they are susceptible (Uematsu et al 1992;Mertely et al 1993a;Beltr an et al 2008). This is generally believed to be due to the extensive root systems produced by plants in the genera Cucurbita and Lagenaria, which can provide sufficient support to the vines and fruits in spite of some infection.…”