GENETICS AND GENETIC IMPROVEMENT OF DISEASE RESISTANCE AND QUALITY TRAITS IN WATERMELON, BROCCOLI, AND LEAFY GREEN BRASSICAS
Location: Vegetable Research
Title: Identification and Utility of Markers Linked to the Zucchini Yellow Mosaic Virus Resistance Gene in Watermelon
Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 9, 2009
Publication Date: September 15, 2009
Citation: Harris, K.R., Ling, K., Levi, A., Wechter, W.P. 2009. Identification and Utility of Markers Linked to the Zucchini Yellow Mosaic Virus Resistance Gene in Watermelon. Journal of the American Society for Horticultural Science. 134:529-534.
Interpretive Summary: Watermelon is an economically important crop in the United States with an annual production of 4.2 billion pounds. Zucchini yellow mosaic virus-Florida strain (ZYMV-FL) is a major limitation to commercial watermelon production in the entire United States, causing serious damage and reduction in watermelon yield and quality. In cucurbits, several strategies have been employed in an effort to control viruses, from the use of insecticides to reduce the population of insects that spread the virus, to genetic transformation of plants. The most economic and publicly accepted method is incorporating virus resistance genes from resistant wild cucurbits into commercially acceptable plant lines by conventional breeding. The laborious breeding and resistance screening procedure can be simplified by employing marker-assisted selection (MAS), which uses DNA markers to track incorporation of the resistance gene(s) during the breeding process. We have identified two markers associated with the gene for ZYMV-FL resistance in watermelon. Furthermore, we have found these markers to be useful in tracking the incorporation of the resistance gene from a ZYMV-FL resistant wild watermelon plant into a susceptible watermelon cultivar using traditional breeding. These DNA markers will be useful to plant breeders and seed companies in MAS-breeding programs to more efficiently incorporate the ZYMV-FL resistance gene into agriculturally acceptable watermelon cultivars.
Zucchini yellow mosaic virus (ZYMV) is one of the most economically important viruses affecting watermelon in the United States. The ZYMV-Florida strain (ZYMV-FL) is considered a major limitation to commercial watermelon production in the entire United States. Experiments with F2 and BC1 plants, derived from a cross between the ZYMV-FL resistant Plant Introduction PI 595203 and the ZYMV-FL susceptible cultivar New Hampshire Midget (NHM), indicated that the resistance to ZYMV-FL is conferred by a homozygous recessive gene. In this study, we identified a marker ‘ZYRP’ (ZYMV Resistant Polymorphism) linked to the ZYMV-FL resistance gene locus (8.0 cM in an F2 population, and 13.0 cM in a BC1). The identification of a single nucleotide polymorphism (SNP) within the ZYRP sequence allowed the development of a sequence characterized amplification region (SCAR) marker, SNP190. Based on our genetic mapping studies, it appears that the gene which confers resistance to ZYMV-FL is not linked to a reported homozygous recessive gene which confers resistance to a Chinese strain of ZYMV (ZYMV-CH). Experiments using a BC2F2 population, with ZYMV-FL resistance derived from PI 595203, confirmed that the marker ZYRP is significantly correlated with the resistant phenotype. Moreover, we showed markers linked to the ZYMV-FL resistance gene in watermelon also amplified in several other genera of Cucurbitaceae. This report describes the identification of single-reaction, PCR-based markers linked to ZYMV-FL resistance in watermelon. These markers should prove useful in marker-assisted breeding programs for ZYMV-FL resistance, as well as show considerable potential for use in other genera of Cucurbitaceae.