DESIGN AND USE OF A SIMULATION-MODEL TO EVALUATE GERMPLASM FOR ANTIBIOTIC-RESISTANCE TO THE GREENHOUSE-WHITEFLY (TRIALEURODES-VAPORARIORUM)AND THE SWEET-POTATO WHITEFLY (BEMISIA-TABACI)

SARAH (Software for the Assessment of antibiotic Resistance to Aleyrod idae in Host plants) is a deterministic simulation model of whitefly p opulation growth based on whitefly life-history components determined on individual plants. The life-history components recorded were ovipos ition late, adult survival, pre-adult survival, developmental period, and sex ratio. The simulation model serves as a tool to combine these components and to obtain a single criterion for (antibiotic) resistanc e. The criterion used was the decrease in simulated intrinsic populati on growth rate, r(s), relative the r(s) value determined on a suscepti ble control genotype. This model-based evaluation method was tested us ing the greenhouse whitefly. Trialeurodes vaporariorum Westwood, on to mato and the sweetpotato whitefly, Bemisia tabaci Gennadius, on tomato , eggplant, collard, and pepper. To study its consistency over time, t he evaluation method was repeated six times for T. vaporariorum on a s usceptible and a resistant tomato cultivar. Simulated intrinsic popula tion growth rate was more consistent in indicating resistance than any of the individual life-history components. Of ten L. hirsutum accessi ons tested for resistance to T. vaporariorum, three exhibited r(s) val ues that were significantly lower than those for the susceptible contr ol. In addition, on these ten L. hirsutum accessions, a significant po sitive correlation was observed between r(s) and sex ratio (# females/ # males). Four host plant species (tomato, collard, eggplant, and pepp er) were evaluated for resistance to B. tabaci. All life-history compo nents and r(s) values varied among host species, while a negative r(s) value was observed for B. tabaci on pepper. A high correlation was fo und between results from a sensitivity analysis of SARAH and results f rom a sensitivity analysis of a validated whitefly population simulati on model by Yano et al. (1989a). Significant correlations were found f or the relationships between oviposition rate, adult survival, or pre- adult survival and r(s), indicating that none of these life-history co mponents can be omitted from the test procedure. This model-based eval uation method offers a standardized way to quantify levels of antibiot ic resistance to whiteflies and will enhance efficiency in breeding pr ograms.