Volatile-mediated resistance in watermelon against whiteflies

The whitefly (Bemisia tabaci) is a destructive pest of cucurbits and many other crops, leading to

significant yield losses in cultivated watermelon (Citrullus lanatus). This study investigates the

volatile-mediated resistance of Citrullus colocynthis, a wild desert relative, using behavioral

bioassays and volatile organic compound (VOC) profiling. No-choice oviposition and Y -tube

olfactometer assays revealed that selected accessions had significantly reduced whitefly attraction

and oviposition compared to susceptible commercial cultivars ‘Sugar Baby’ and ‘Crimson Sweet.’

GC-MS analysis showed that resistant genotypes emitted higher levels of sesquiterpenes (E)-β-

caryophyllene, α-humulene, and germacrene D, compounds previously linked to herbivore

deterrence. In contrast, susceptible cultivars produced higher concentrations of monoterpenes and

green leaf volatiles, which are often associated with herbivore attraction. Principal component

analysis (PCA) demonstrated clear separation between resistant and susceptible genotypes based

on their VOC profiles. These findings provide evidence that C. colocynthis exhibits volatile-

mediated resistance to whiteflies and highlight its potential as a genetic resource for developing

pest-resistant watermelon cultivars. This work advances sustainable pest management strategies

and contributes to integrated pest management (IPM) frameworks.