Leaf Volatiles: Identification for Whitefly Resistance in Watermelon

Commercial watermelon cultivars (Citrullus lanatus var. lanatus) share a narrow genetic base and are susceptible to many insects and diseases, including whiteflies that have been causing serious economic damages to this important cucurbit crop.  However, several United States Plant Introduction accessions (PIs) of the desert watermelon Citrullus coloccynthis were identified as resistant to whiteflies. No information is available in the literature on the volatile constitutes of Citrullus coloccynthis relative to watermelon cultivars. The Citrullus coloccynthis germplasm collection was surveyed in comparison to watermelon cultivars for volatile compounds that may be associated with resistance to whiteflies. The volatile components of leaf explants were obtained by headspace solid-phase microextraction (HP-SPME) and combined with gas chromatography-mass spectrometry (GC-MS) for identification.