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Title: Utilizing Citrullus lanatus var. citroides germplasm for developing tetraploid lines useful as rootstocks and in breeding programs of seedless watermelon lines

Author
item Levi, Amnon
item Thies, Judy
item Wechter, William - Pat
item Kousik, Chandrasekar - Shaker
item Harrison Jr, Howard
item Weng, Yiqun
item HASSELL, RICHARD - Clemson University

Submitted to: Cucurbitaceae Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 10/16/2014
Publication Date: 10/26/2014
Citation: Levi, A., Thies, J.A., Wechter, W.P., Kousik, C.S., Harrison Jr, H.F., Weng, Y., Hassell, R. 2014. Utilizing Citrullus lanatus var. citroides germplasm for developing tetraploid lines useful as rootstocks and in breeding programs of seedless watermelon lines. Cucurbitaceae Proceedings. 27:A48.

Interpretive Summary: N/A

Technical Abstract: In recent years, soil-borne diseases and pests have intensified in watermelon, particularly after the phasing out of the soil fumigant methyl bromide, and there is a continuous need to develop solutions for reducing the disease and pest pressure in this important cucurbit crop. Grafting of watermelons onto Cucurbita rootstocks, as a means for reducing damage by soil-borne diseases, has been practiced throughout the world, particularly in Asia and the Mediterranean region. However, Cucurbita rootstocks are highly susceptible to root-knot nematodes and frequently have adverse effect on watermelon fruit quality. United States Plant Introduction accessions (PIs) representing Citrullus lanatus (Thunb.) Matsum. & Nakai var. citroides (L. H. Bailey) Mansf. (CLC) exhibit resistance to root-knot nematodes and/or Fusarium wilt. Our recent studies in Charleston, South Carolina (2009-2012) showed that seedless (triploid) watermelon cultivars produced higher yield when grafted onto CLC rootstocks compared with those grafted onto commercial squash (Cucurbita spp.) or Lagenaria siceraria (bottle gourd) rootstocks. These results led to our hypothesis that novel tetraploid CLC lines would provide rootstocks with greater root system capacity and vigor, and better disease protection (e.g., against root-knot nematodes and Fusarium wilt) of grafted watermelon scions compared to what could be provided by conventional diploid CLC or by other commonly used rootstocks (e.g., bottle gourds or squash). In this study, we examine the concept of using tetraploid CLC genotypes as rootstocks and in breeding programs of tetraploid lines useful in the development of seedless watermelon varieties.