Screening cultivated eggplant and wild relatives for resistance to sweetpotato whitefly ( Bemisia tabaci ) and to two-spotted spider mite ( Tetranychus urticae )

Whiteflies and spider mites are amongst the most harmful eggplant ( Solanum melongena ) pests. Considering the need for reduction of chemical applications for whitefly and spider mite control, the exploitation of wild relatives of eggplant as sources of pest resistances represents an important strategy in order to improve cultivated eggplant. The objectives of this study were to evaluate 15 accessions from 11 species of eggplant wild relatives together with seven S. melongena accessions for resistance to sweet potato whitefly ( Bemisia tabaci ) and to two-spotted spider mite ( Tetranychus urticae ). Resistance to whitefly was evaluated based on number of eggs, nymph, puparium and whitefly adults in a choice bioassay, while for two-spotted spider mite it was based on leaf damage scores in the choice and no-choice bioassays. The results revealed significantly ( P < 0.05) different levels of resistance to the two pests among the accessions evaluated. Considering all screening parameters in the whitefly choice bioassay, the highest levels of resistance in wild eggplant relatives were detected in Solanum dasyphyllum (DAS1) and S. pyracanthos (PYR1), although one of the cultivated S. melongena (MEL2) accessions also displayed similar resistance levels. In addition, S. campylacanthum (CAM8) and S. tomentosum TOM1 were also resistant to whitefly based on numbers of puparium and adult whiteflies. Two accessions of S. sisymbriifolium (SIS1 and SIS2) exhibited strong resistance to two-spotted spider mite based on the choice and no-choice bioassays. High levels of spider mite resistance were also detected in the no-choice assay in S. dasyphyllum (DAS1) and S. torvum (TOR2) accessions. These resistant accessions can be used in pre-breeding program aiming to breed pest-resistant cultivars in cultivated eggplant. Moreover, to our knowledge, this study represents the first report on potential sources of resistance to whitefly and two-spotted spider mite in wild relatives of eggplant.