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Title: Response of Watermelon Germplasm to Southern Root-Knot Nematode in Field Tests

item Ariss, Jennifer
item Thies, Judy
item Kousik, Chandrasekar - Shaker

Submitted to: HortScience
Publication Type: Abstract Only
Publication Acceptance Date: 2/8/2008
Publication Date: 6/1/2008
Citation: Ariss, J., Thies, J.A., Kousik, C.S., Hassell, R.L. 2008. Response of Watermelon Germplasm to Southern Root-Knot Nematode in Field Tests. HortScience. 43(3):622.

Interpretive Summary:

Technical Abstract: Southern root-knot nematode (Meloidogyne incognita) is a serious pest of cultivated watermelon (Citrullus lanatus var. lanatus) in southern regions of the US. While there is no known resistance to southern root-knot nematode in watermelon cultivars to date, wild watermelon relatives (C. lanatus var. citroides) have been shown in greenhouse studies to possess various degrees of resistance to root-knot nematode species. In order to evaluate levels of resistance of C. lanatus var. citroides in field tests, two experiments were undertaken over two years to assess experimental lines in artificially infested field sites. In the first study (2006), 21 experimental lines of C. lanatus var. citroides derived from Plant Introduction accessions (USDA, ARS, GRIN) were compared with susceptible entries of C. colocynthis and watermelon cultivars. Of the wild watermelon lines, two entries (USVL-303 and USVL-315) exhibited significantly less galling than all other entries. Five of the best performing C. lanatus var. citroides experimental lines were evaluated with and without pre-plant methyl bromide fumigation at the same field site 2007. Overall, most entries of C. lanatus var. citroides performed similarly with and without pre-plant methyl bromide treatment in regard to root galling, visible egg masses, root vigor, and root mass than watermelon cultivars or C. colocynthis. In both years of field evaluations, most C. lanatus var. citroides lines showed lesser degrees of nematode reproduction and higher root vigor and root mass, with USVL-303 consistently being one of the best performers. The results of these two field evaluations suggest wild watermelon populations may be useful sources of resistance to southern root-knot nematode.