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Title: Sources of Resistance to Zucchini Yellow Mosaic Virus in Lagenaria Siceraria Germplasm

item Ling, Kai-Shu
item Levi, Amnon

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/25/2007
Publication Date: 8/9/2007
Citation: Ling, K., Levi, A. 2007. Sources of Resistance to Zucchini Yellow Mosaic Virus in Lagenaria Siceraria Germplasm. HortScience. 42(5):1124-1126.

Interpretive Summary: Zucchini yellow mosaic virus (ZYMV) is a destructive virus disease on cucurbit crops, including cucumber, pumpkin, squash, watermelon and bottle gourd. The disease could result in total yield loss in a susceptible cultivar if appropriate control measures are not taken. Unfortunately, the chemical control of virus transmitting insect (aphid) may not always be effective for virus disease control due to the development of pesticide-resistant insect population and the increasing environmental and human safety concerns. On the other hand, some other effective insecticides may not be labeled for minor cucurbit crops, such as bottle gourd. Therefore the best solution in controlling a virus disease is through the use of disease resistant cultivars. The first step in developing a resistant cultivar is to identify a source(s) of genetic resistance from the germplasm collection. Based on earlier studies by others, sources of genetic resistance to ZYMV are available in bottle gourd species (Lagenaria siceraria) from other parts of the world. However, there has not been a systemic evaluation of USDA bottle gourd germplasm for its resistance to major cucurbit viruses, including ZYMV. In this study, we made an effort to screen all the available U.S. bottle gourd germplasm collection (190 accessions) for their resistance to ZYMV. Surprisingly, a high percentage of the U.S. bottle gourd germplasm (19%) or 36 accessions were resistance to ZYMV. Identification of many sources of genetic resistance to ZYMV will provide breeders more freedom to choose and breed for locally adapted virus resistant bottle gourd cultivars. In recent years, bottle gourd has become one of the important rootstock species in an ever increasing production of grafted watermelon in the United States.

Technical Abstract: One hundred ninety United States Plant Introductions (PIs) of bottlegourd, Lagenaria siceraria (Mol.) Standl., were evaluated for their resistance against the Florida strain of Zucchini yellow mosaic virus (ZYMV-FL). Two-week old seedlings were mechanically inoculated on cotyledons and the first true leaf using freshly prepared ZYMV-FL tissue extract. To insure sufficient inoculation, the seedlings were re-inoculated two weeks after the first inoculation. Two weeks after the second inoculation, tested plants were visually evaluated for ZYMV symptoms and leaf samples were collected from each plant for serological analysis with enzyme-linked immunosorbent assay (ELISA). The results in the primary screening showed that a high percentage (19%) of U.S. L. siceraria germplasm or 36 accessions were resistant to ZYMV-FL infection, with another 64 PIs in partial resistance, and the rest 90 PIs in susceptible. Interestingly, a majority of these ZYMV resistant L. siceraria PIs (33 of 36) was collected in India. The ZYMV-FL resistance was confirmed in a repeated test using a portion of representative accessions, including 10 susceptible, three partial resistant, and three resistant PIs. The resistance was inheritable to progenies of the five resistant PIs generated through single plant selection as well as their hybrids.