ARS | Publication request: Resistance of Wild Watermelon (Citrullus lanatus var. citroides) Rootstocks to Southern Root-Knot Nematode

Submitted to: HortScience
Publication Type: Abstract Only
Publication Acceptance Date: March 7, 2010
Publication Date: N/A

Technical Abstract: Seedless watermelon (Citrullus lanatus var. lanatus) ‘Tri-X 313’ scions were grafted on ten different cucurbit rootstocks and evaluated in a field infested with southern root-knot nematode (RKN), Meloidogyne incognita, in Charleston, SC in 2009. The rootstocks evaluated included five wild watermelon (Citrullus lanatus var. citroides) germplasm lines (RKVL 301, RKVL 302, RKVL 303, RKVL 316, and RKVL 318), one bottle gourd (Lagenaria siceraria ‘Emphasis’), one squash hybrid (Cucurbita moschata x C. maxima ‘Strong Tosa’), one commercial watermelon rootstock (C. lanatus var. citroides ‘Ojakkyo’), and three wild tinda (Praecitrullus fistulosus) rootstocks. Self-grafted ‘Tri-X 313’ and non-grafted ‘Tri-X 313’ were included as checks. RKN infection was severe in ‘Emphasis’ bottle gourd, ‘Strong Tosa’ hybrid squash, and the three wild tinda rootstocks with percentages of root system galled ranging from 86 to 100 percent. The five RKVL wild watermelon lines exhibited significantly lower (P<0.05) percentages of root galling (range: 9.1 to 16.2 percent) than non-grafted ‘Tri-X 313’ (40.9 percent), ‘Emphasis’, ‘Strong Tosa’, and the wild tinda rootstocks. RKVL 301, RKVL 303, RKVL 316, and RKVL 318 wild watermelon rootstocks had significantly greater (P<0.05) amounts of fibrous roots than all other entries. The grafted wild watermelon rootstock RKVL 318 produced significantly more (P<0.05) fruit (12 per plot) than all other entries (mean = 5.3 per plot), and it produced a heavier (P<0.05) fruit yield (29.5 lbs per plot) than all entries except self-grafted ‘Tri-X 313’ (21.5 lbs per plot). The results of the present study suggest that the RKVL wild watermelon rootstocks (C. lanatus var. citroides) possess durable resistance to root-knot nematodes in the field and may provide a new alternative to pre-plant soil fumigation for managing RKN in watermelon.