Adaptation of Bemisia tabaci biotype B (Gennadius) to cassava, Manihot esculenta (Crantz)

Abstract

Bemisia tabaci is a recognized pest in cassava ( Manihot esculenta) crops in Asia and Africa, where it transmits the cassava mosaic geminiviruses (CMGs) (family: Geminiviridae, genus: Begomovirus). A general consensus exists that B. tabaci is a complex of morphologically indistinguishable populations with different biological biotypes. In the Americas, though the polyphagous B. tabaci biotype B appears to feed on cassava, it is postulated that the absence of CMGs is related to the inability of this biotype to colonize this crop effectively. However, its potential adaptation is considered a threat for cassava production in the Neotropics. This study was initiated to verify whether B. tabaci can become gradually adapted to M. esculenta. Trials in rearing chambers were carried out measuring population development of whitefly individuals passed through a series of intermediate hosts, previously selected and based on phylogenetic closeness to Manihot. The capacity of biotype B to adapt gradually to cassava, started on a legume ( Phaseolus vulgaris), followed on two Euphorbiaceae ( Euphorbia pulcherrima and Jatropha gossypiifolia) until, finally reaching a commercial cassava variety. B. tabaci female mean longevity on cassava, coming from P. vulgaris, E. pulcherrima and J. gossypiifolia was 3.1, 5.6 and 3.3 days, respectively. The highest oviposition rate (2.6 eggs/female/2 days), the shortest development time (44.4 days) and the highest value of r m (0.48 day −1) were for populations coming from J. gossypiifolia, where 27.5% of the individuals coming from this host survived and reproduced on cassava. The importance and potential impact of phylogenetically close plants as intermediate hosts faciliting the adaptation of B. tabaci biotype B to cassava is discussed.