Project Number: 6659-21000-017-00
Project Type: Appropriated

Start Date: May 19, 2008
End Date: May 18, 2013

Objective:
1. Determine the genetic control of resistance to important diseases and pests of watermelon and release resistant breeding lines developed. 1.A. Determine genetic control of root-knot nematode (Meloidogyne incognita) resistance in watermelon; identify and map DNA-based markers closely linked to the resistance locus (loci). 1.B. Determine genetic control of Fusarium wilt (Fon race 2) resistance in watermelon; identify and map DNA-based markers closely linked to the resistance locus (loci). 2. Utilize genomic tools to develop genetic linkage maps for watermelon and diagnostic DNA-based markers for host-plant resistance to viruses and key watermelon fruit traits. 2.A. Map and isolate DNA sequences associated with Zucchini Yellow Mosaic Virus (ZYMV) resistance in watermelon. 2.B. Identify and map DNA sequences associated with watermelon fruit quality traits (e.g., fruit size and shape, flesh color and texture, carotenoid levels, and soluble content). 3. Develop lines of broccoli improved for economically important traits. 3.A. Develop inbred broccoli lines with tolerance to high temperature stress, elucidate the underlying genetic control of the tolerance, and identify quantitative trait loci (QTL) and associated DNA-based markers for the tolerance. 3.B. Breed high yielding, self-compatible inbred broccoli lines with high productivity and high levels of health-promoting compounds (e.g., glucoraphanin) as compared to that of standard hybrid cultivars. 4. Elucidate the genetic control of bacterial leaf spot resistance in leafy green Brassicas (B. juncea and B. rapa), identify DNA markers closely linked to the resistance locus (loci), and release resistant breeding lines developed in this project. 5. Develop pinkeye-type southernpea (cowpea) lines that exhibit yield potential equivalent to leading blackeye-type cultivars.

Approach:
Select parental lines of watermelon, broccoli, or leafy green brasscias based on phenotypic expression of resistance, tolerance, or quality traits under study. Use the selected parents to construct conventional (i.e., F2, BC1, recombinant inbred) and doubled haploid (for broccoli only) populations that segregate for the traits of interest, and then employ those populations in studies to determine mode of inheritance of each character. Utilize PCR-based markers and other genomic technologies to identify sequences linked to the studied characters and to locate controlling genes on linkage maps. Use particular markers (i.e., SSR, SRAP, SNPs, or SCARs) closely associated with traits of interest to develop tools for marker-assisted selection. Based on knowledge gained through above studies, devise breeding strategies, and applications of marker technologies to use in the further development of horticulturally enhanced lines or hybrids that express resistances and other traits of interest and that also produce high quality vegetables. Make enhanced lines available through public releases or commercial licensing. Continue ongoing searches for new resistances and tolerances among watermelon and vegetable Brassica accessions from the U.S. PI and other collections. In addition to the above, the southernpea pinkeye-type cultivar GreenPack-DG and the high-yielding blackeye bean cultivar California Blackeye No. 46 will be used as the parental lines to initiate a plant breeding project with the major goal of breaking the apparent yield barrier in pinkeye-type southernpeas; the two cultivars will be crossed and pedigree and single-seed-descent breeding procedures will be employed to quickly advance progeny populations three generations per year (spring field cycle, fall field cycle, and a winter greenhouse cycle).