Genetic Enhancement of Watermelon, Broccoli, and Leafy Brassicas for Economically Important Traits
Project Number: 6659-21000-018-00
Start Date: May 19, 2013
End Date: May 18, 2018
1. Devise sequence-based markers to accelerate the transfer of new sources of resistance to Fusarium wilt and potyviruses from wild to cultivated watermelon types.
1.A. Utilize watermelon genome sequence to develop a single nucleotide polymorphism (SNP)-based linkage map for the citron watermelon, identifying markers associated with Fusarium wilt (FW) and Papaya ring spot virus (PRSV) resistances.
1.B. Develop a SNP-based genetic linkage map for the cultivated type watermelon (C. lanatus var. lanatus) which includes markers associated with PRSV resistance and also fruit attributes.
2. Develop and release watermelon germplasm with improved resistance to Fusarium wilt and potyviruses combined with improved phytonutrient content.
2.A. Develop and release watermelon germplasm exhibiting FW, race 2 resistance from the wild “citron” combined with attributes (e.g. presence of lycopene) of cultivated watermelon.
2.B. Develop and release watermelon germplasm exhibiting resistance to Zucchini yellow mosaic virus (ZYMV) combined with attributes of cultivated watermelon.
3. Breed and release broccoli lines with enhanced tolerance to high temperature stress by incorporating additional, new tolerance genes, and develop broccoli with divergent levels of health promoting compounds.
3.A. Breed and release broccoli lines with enhanced tolerance to high temperature by exploiting additional, new tolerance alleles, and identify genomic sequences associated with the tolerant phenotype.
3.B. Develop genetically similar broccoli lines with divergent levels of glucoraphanin useful for studying the human health promoting effects of this vegetable.
4. Exploit genotypic and phenotypic diversity in leafy green Brassica germplasm to develop lines with resistance to bacterial leaf disease and enhanced levels of health promoting compounds.
4.A. Develop an inbred line of leafy mustard green (B. juncea) with resistance to Pseudomonas cannabina pv. alisalensis (Pca) and improved horticultural phenotype, and a line of B. rapa with resistance to Pca.
4.B. Examine genotypic and phenotypic diversity in a unique collection of collard landraces collected from southern seed savers, and identify useful sources of disease resistance and phytonutrient profiles in this germplasm.
Select parental lines of watermelon, broccoli or leafy green Brassicas based on phenotypic expression of resistance, tolerance or quality traits under study. Use the selected parent lines to construct conventional (i.e., F2, BC1, recombinant inbred) and doubled haploid (for broccoli only) populations segregating for the traits of interest, and then employ those populations in studies to determine mode of inheritance of each character or to select superior lines. Utilize PCR-markers and other genomic technologies, such as genotype by sequencing, to identify sequences linked to the studied characters and to locate controlling genes on linkage maps. Use particular markers (e.g., SSRs, SNPs, or SCARs) closely associated with traits of interest to develop tools for marker-assisted selection. Based on knowledge gained through the 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 or tolerances among watermelon and vegetable Brassica accessions from the U.S. Plant Introduction and other collections.