Citrullus ecirrhosus: wild source of resistance against Bemisia tabaci (Hemiptera: Aleyrodidae) for cultivated watermelon

Authors: Simmons, Alvin; Jarret, Robert - Bob; Cantrell, Charles; Levi, Amnon

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/4/2019
Publication Date: 4/23/2019
Citation: Simmons, A.M., Jarret, R.L., Cantrell, C.L., Levi, A. 2019. Citrullus ecirrhosus: Wild source of resistance against Bemisia tabaci (Hemiptera: Aleyrodidae) for cultivated watermelon. Journal of Economic Entomology. https://doi.org/10.1093/jee/toz069.
DOI: https://doi.org/10.1093/jee/toz069

Interpretive Summary: Whiteflies are major insect pests that cause serious damage and limit watermelon crop production in the USA by feeding injury and by transmitting plant viruses. There is a continuous need to identify natural resources useful for improving watermelon cultivars for resistance to whiteflies. We conducted a study to determine if Citrullus ecirrhosus, a wild relative of watermelon that grows in the desert in Southern Africa, may be a source of resistance to whitefly. We found that the C. ecirrhosus attracts less whiteflies than the cultivated watermelon, which may be due to the strong aromatic compounds exuded by the wild species. Additionally, whiteflies grown on C. ecirrhosus plants had lower survival and were smaller than whiteflies grown on cultivated watermelon. We also demonstrated that traditional breeding methods can be used to cross this wild Citrullus species plants with cultivated watermelon and produce viable seeds. The results of this study will be useful for researchers interested in exploring the natural mechanisms associated with whitefly resistance, and in improving watermelons for resistance to this major insect pest.

Technical Abstract: Members of the highly polyphagous Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) species complex cause major crop damage by feeding and by transmitting plant viruses. The Middle East-Asia Minor 1 (MEAM1) of the B. tabaci complex is by far the most problematic whitefly affecting crops including the cultivated watermelon (Citrullus lanatus). Watermelon cultivars share a narrow genetic base and are highly susceptible to whiteflies. However, there is wide genetic diversity among the species of Citrullus. A wild relative of the cultivated watermelon is C. ecirrhosus; it is a perennial desert species. We conducted a study to assess the potential of C. ecirrhosus as a source of whitefly resistance for cultivated watermelon. Results of this study indicate that C. ecirrhosus offers resistance against the MEAM1 B. tabaci based on, at least, antibiosis and antixenosis. Whitefly performance based on developmental survival, body size attainment, and non-preference were suppressed as compared with the watermelon cultivar Sugar Baby. Our ofactometer data support our other non-preference results. However, no detrimental effect of pungent odor from the leaves was observed on adult whitefly survival. We further demonstrated that plants of C. ecirrhosus can be clonally propagated from vine cuttings of the parent. Moreover, using traditional breeding procedures, we were able to cross C. ecirrhosus with cultivated watermelon and produce viable seeds. This study is the first report to establish pest resistance in C. ecirrhosus. This wild species offers a source of resistance against whiteflies for cultivated watermelon.