Submitted to: HortScience
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/22/2005
Publication Date: 4/1/2006
Citation: Levi, A., Thomas, C.E., Thies, J.A., Simmons, A.M., Ling, K., Harrison Jr, H.F. 2006. Novel watermelon bredding lines containing chloroplast and mitochondrial genomes derived from the desert species citrullus colocynthis. HortScience. 41:463-464. Interpretive Summary: Watermelon is a major vegetable crop grown in 44 states in the U.S. Annual watermelon production has increased from 1.2M tons in 1980 to 3.9M tons in 2003 with a farm value of $310 million. In recent years, there has been an increased demand for seedless watermelon. As a result, over 60% of the watermelons produced in the U.S. during 2004 were seedless types. There is a continuous need to develop new seedless watermelon varieties suitable to consumer demands. Most of the watermelon cultivars developed in the U.S. during the last 200 years have a similar genetic background, and are susceptible to a large number of diseases and pests. In this study, we attempted to broaden the genetic diversity of watermelon cultivars by crossing them with wild watermelons collected in different part of the world. Our experiments produced new watermelon lines with unique fruit qualities that can be useful for plant breeders and seed companies in their experiments to develop new varieties of seedless watermelons with wider genetic diversity.
Technical Abstract: Three watermelon breeding lines, USVL-200, USVL-205 and USVL-210, have been developed at the USDA, ARS, U.S. Vegetable Laboratory, Charleston, SC. These lines contain the nuclear genome of watermelon cultivars (Citrullus lanatus var. lanatus) and chloroplast and mitochondrial genomes derived from the desert species Citrullus colocynthis. USVL-200 was produced by first crossing a F1 hybrid [‘New Hampshire Midget’ (C. lanatus var. lanatus) x Griffin 14113 (C. lanatus var. citroides)] with C. colocynthis PI 386015 which was used as the female parent. Then, most of the nuclear genes of the hybrid plant were replaced with nuclear genes of cultivated watermelon (C. lanatus var. lanatus) through eight backcrosses with different watermelon cultivars. A BC8-plant was self-pollinated and a plant with a globular fruit, dark green rind, and yellow flesh was selected in five successive generations to produce USVL-200 seeds (BC8S6). USVL-205 is a sister line of USVL-200. However here, a BC8-plant was self-pollinated and a plant with a red flesh fruit was selected in six successive generations to produce USVL-205 seeds (BC8S7). The fruits of USVL-200 and USVL-205 are ready for harvest in early to mid-season. USVL-210 was produced by first crossing ‘Charleston Gray’ (C. lanatus var. lanatus) with C. colocynthis PI 386016 (female parent). Then, most of the nuclear genes of the hybrid plant were replaced with these of cultivated watermelon through a series of successive backcrosses with the watermelon cultivars. A BC6-plant was self-pollinated, followed by self-pollination and selection of the plant with best fruit quality in five successive generations to produce USVL-210 seeds (BC6S6). USVL-210 is a ‘Charleston Gray’ type producing 2.6-3 oblong fruits with pink flesh color, ready for harvest in mid to late-season.