Screening Cucurbit Rootstocks for Resistance to Meloidogyne spp. and Rotylenchulus reniformis

Abstract

Fusarium wilt [caused by the fungus Fusarium oxysporum f. sp. niveum (FON)] has been a consistent problem in watermelon [Citrullus lanatus (Thunb.) Matsum. and Nakai] production worldwide. One method for combatting this pathogen in the field is to graft a susceptible, high-yielding scion on to a fusarium wilt-resistant rootstock. A concerning issue with rootstocks resistant to fusarium wilt is that they have not been tested for their susceptibility to plant pathogenic nematodes-specifically, root-knot nematodes (RKNs; Meloidogyne spp.) and the reniform nematode (Rotylenchulus reniformis). Preliminary findings have demonstrated that many of these Fusariumresistant rootstocks are highly susceptible to RKNs. Research was conducted during the Spring and Fall 2015 and 2016 to evaluate the resistance to RKN and reniform nematode in rootstocks with known resistance to fusarium wilt. Six rootstocks were evaluated over the course of four experiments. A nematode-susceptible interspecific hybrid [Cucurbita maxima (Duchesne) 3 C. moschata (Duchesne)] rootstock 'Carnivor' was included as a susceptible control in both years. Results demonstrated that several Citrullus lanatus var. citroides (L.H. Bailey) rootstocks ('Carolina Strongback', USVL246-FR2, USVL252-FR2, and USVL-360) and 'SP-6' (a commercially available pollinizer cultivar) exhibited resistance to plant parasitic nematodes when compared with the susceptible control. Partial resistance was observed in USVL-482351. When compared with the control, these rootstocks also had fewer Meloidogyne spp. and R. reniformis in root tissue. These findings indicate that rootstocks may be available to manage both fusarium wilt and RKN in grafted cucurbit production system.

Resistance of Cucurbita spp. germplasm tothe fungus Macrophomina phaseolina

“…Although the species C. maxima and C. moschata have been used as rootstocks of several other cucurbit species,such as melon (ZHOU et al, 2014), watermelon (SMITH et al, 2019) and cucumber (GORETA BAN et al, 2014), it is important to emphasize that, for being allogamous, the genetic variability of the species is favored (PRIORI et al, 2018), so if adequate rootstocks are not selected, there may be adverse effects as ineffi ciency regarding the control of the pathogen.…”

Genetic characterization of citron watermelon (citrullus lanatus var. citroides [L.H. Bailey] mansf. ex greb.) and development of experimental hybrids.

“…Also, the white-fleshed citron watermelon PI 296341 originating from South Africa was identified to be a promising rootstock for production of sweet dessert watermelon to improve yield, quality, and Fusarium resistance (Edelstein et al, 2014). Some citron watermelon rootstocks USVL246-FR2 (PI 482246) and USVL252-FR2 (PI 482252), which originated from Zimbabwe, are used for commercial production of grafted sweet watermelon in the USA owing to their natural resistance to Fusarium wilt and nematodes (Wechter et al, 2016;Smith et al, 2019). In South Africa, citron watermelon germplasm has not been used as rootstock for sweet dessert watermelon to improve yield and fruit quality, and for biotic and abiotic stress tolerance breeding.…”