Identification and characterization of genetic strains of Bemisia tabaci in Israel and Colombia

These differences are undetectable by conventional taxonomic procedures, but their existence implies that B. tabaci is genetically differentiated and different variants may respond differently to control measures. This finding is very important since the entire global population of B. tabaci is considered one and the same species. The presence of intraspecific differentiation should be taken seriously when quarantine measures are considered. In Israel there was no indication of intraspecific differentiation according to host-plant or geography, but there was a clear difference in enzymatic pattern between samples from insecticide-treated commercial fields and samples from unsprayed control populations. Their difference may be used in monitoring the frequencies of resistant individuals in field populations. In addition to the analysis of genetic variation within one species, electrophoretic markers were developed which can be used to identify adults of different whitefly species in Israel and in Colombia. Whitefly taxonomy is based on morphological characters of the pupal case, and adults of many species of whiteflies are indistinguishable morphologically. The use of electrophoresis for this purpose can help field operators to correctly identify adult whiteflies which may endanger crops by transmission of viral diseases. (There is also a preliminary indication that adults of different species may be identified morphologically using the Scanning Electron Microscope (SEM), where and when this service is available). The project was carried out in full cooperation between Israeli and Colombian (CIAT) scientists. The electrophoretic techniques developed in Israel were transferred to CIAT and used with skill by the local personnel. (The SEM study was done in Colombia only). Overall, this is a very fruitful cooperative study which lays the foundation for further cooperative work in the future. (Author abstract)