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ARS Home » Southeast Area » Charleston, South Carolina » Vegetable Research » Research » Publications at this Location » Publication #359214
Research Project: Biological, Genetic and Genomic Based Disease Management for Vegetable Crops

Location: Vegetable Research

Title: QTL mapping of resistance to bacterial fruit blotch in Citrullus amarus

Author
item Branham, Sandra
item Levi, Amnon
item Katawczik, Melanie
item Wechter, William - Pat

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/19/2019
Publication Date: 5/10/2019
Citation: Branham, S., Levi, A., Katawczik, M.L., Wechter, W.P. 2019. QTL mapping of resistance to bacterial fruit blotch in Citrullus amarus. Theoretical and Applied Genetics. https://doi.org/359214.

Interpretive Summary: Acidovorax citrulli, the causal agent of bacterial fruit blotch (BFB) of cucurbits, has the potential to devastate production of watermelon and other cucurbits. Despite decades of research on host-plant resistance to A. citrulli, no germplasm has been found with immunity and only a few sources with moderate to high levels of BFB resistance have been identified. The majority of these resistant sources are Citrullus amarus (citron melon) plant introductions, a species that crosses readily with cultivated watermelon (Citrullus lanatus L.). To date, no cultivated watermelon is known to have resistance to this disease. Working with a population derived from a cross between two C. amarus lines, BFB resistant (USVL246-FR2) and BFB susceptible (USVL114), we performed analysis to identify six genetic regions associated with resistance. These genetic regions called “quantitative trait loci” (QTL) each explained between 5 and 15% of the variation in BFB resistance within the population. This study represents the first identification of QTL associated with resistance to A. citrulli in any cucurbit. This work will allow for the development of genetic markers that can be used to breed the BFB resistance from USVL246-FR2 into cultivated watermelon, giving growers a new and sustainable control option for this disease.

Technical Abstract: Acidovorax citrulli, the causal agent of bacterial fruit blotch (BFB) of cucurbits, has the potential to devastate production of watermelon and other cucurbits. Despite decades of research on host-plant resistance to A. citrulli, no germplasm has been found with immunity and only a few sources with various levels of BFB resistance have been identified, but the genetic basis of resistance in these watermelon sources are not known. Most sources of resistance are plant introductions (PIs) of Citrullus amarus (citron melon), a closely related species that crosses readily with cultivated watermelon (Citrullus lanatus L.). In this study, we evaluated a recombinant inbred line population (N=200), derived from a cross between BFB resistant (USVL246-FR2) and BFB susceptible (USVL114) C. amarus lines, for foliar resistance to A. citrulli in three replicated greenhouse trials. We found the genetics of BFB resistance to be complicated by strong environmental influence, low heritability and significant genotype-by-environment interactions. QTL mapping of affected leaf area identified six QTL that each explained between 5 and 15% of the variation in BFB resistance in the population. This study represents the first identification of QTL associated with resistance to A. citrulli in any cucurbit.