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Title: Root-knot nematode resistant rootstocks for grafted watermelon

item Thies, Judy
item Ariss, Jennifer
item HASSELL, R - Clemson University
item Levi, Amnon

Submitted to: Acta Horticulturae
Publication Type: Proceedings
Publication Acceptance Date: 5/15/2012
Publication Date: 10/11/2012
Citation: Thies, J.A., Ariss, J., Hassell, R.L., Levi, A. 2012. Root-knot nematode resistant rootstocks for grafted watermelon. Acta Horticulturae. pp. 201-211.

Interpretive Summary: N/A

Technical Abstract: Rootstock lines of wild watermelon (Citrullus lanatus var. citroides) with resistance to root-knot nematodes (RKN) were developed by our team at the U.S. Vegetable Laboratory. Rootstock lines RKVL 301, RKVL 316, and RKVL 318 (RKVL = Root Knot Vegetable Laboratory) were compared to wild tinda (Praecitrullus fistulosus) and commercial cucurbit rootstocks for grafted seedless triploid watermelon (C. lanatus var. lanatus) ‘Tri-X 313’ in fields infested with southern RKN (Meloidogyne incognita) in Charleston, SC in two tests. In both tests, RKN infection was severe in ‘Emphasis’ bottle gourd (Lagenaria siceraria), ‘Strong Tosa’ hybrid squash (Cucurbita maxima x C. moschata), and wild tinda rootstocks (root galling range: 86% to 100%). In Test 1, RKVL wild watermelon rootstocks exhibited lower (P<0.05) root galling (range: 9% to 16%) than non-grafted ‘Tri-X 313’ (41%), ‘Emphasis’ (86%), ‘Strong Tosa’ (99%), and wild tinda (96%) rootstocks. The RKVL 318 rootstock produced higher fruit yield (29.5 kg/plot of 6 plants) (P<0.05) than all other rootstocks (mean = 11.0 kg/plot), except for self-grafted ‘Tri-X 313’ watermelon (21.5 kg/plot). In Test 2, one-half of the plots were treated with 392 kg/ha methyl bromide (50%): chloropicrin (50%) before planting. The RKVL wild watermelon rootstocks exhibited root galling ranging from 11% for RKVL 316 to 56% for RKVL 301 in untreated plots. In untreated plots, RKVL 301, RKVL 316, and RKVL 318 rootstocks produced significantly higher fruit yields (21.9, 25.6, and 19.9 kg/plot, respectively) (P<0.05) than ‘Strong Tosa’ (3.0 kg) or ‘Ojakkyo’ watermelon rootstock (2.8 kg). Yields of watermelon grafted on ‘Strong Tosa’ were nearly 7X greater (P<0.05) in methyl bromide plots than untreated plots. However, RKVL 316 and RKVL 318 produced similar yields in both treatments, while RKVL 301 rootstock produced higher fruit yield (P<0.05) in untreated plots than in methyl bromide plots. RKVL 316 had low root galling and produced the highest yield compared with any other rootstock evaluated. The three RKVL wild watermelon lines should be useful rootstocks for grafted watermelon, and useful germplasm sources for developing RKN-resistant watermelon breeding lines and cultivars.