Host associated genetic variations in whitefly, Bemisia tabaci (Genn.)

Genetic variability due to host plants was studied in whitefly, Bemisia tabaci (Genn.), populations that were collected from fields of different crops (cotton, brinjal, potato, tomato and soyabean) and a weed (Sida sp.), and maintained on their respective host plants for 12 generations. Comparative RAPD-PCR analysis of these populations led to identification of 85 different polymorphic bands or host specific markers. Of these, 39 markers were identified for single-host specificity; maximum markers were identified for tomato (14) and cotton (13); followed by brinjal (5), Sida sp. (4) and soyabean populations of whitefly (3). Similarly, of 23 two-host specific markers, maximum markers were identified in cotton (10) and tomato (11) whitefly. This is the first report establishing the existence of host-plant specific genotypes in B. tabaci that is likely to have broad impact on its pest status and vectoring ability for different geminiviral diseases. The genetic similarity dendrogram based upon the comparative RAPD profiles showed the existence of a high level of genetic relatedness (7285%) amongst the investigated whitefly types and the lineage of their origin from a common type. This lineage suggests that the whitefly types holding specificity for different host plants under study have evolved as three distinct genetic groups formed by cotton, Sida and soyabean (Group 1); potato and brinjal (Group 2); and tomato (Group 3).