Resistance to Western Flower Thrips Feeding Damage in Impatiens Populations from Costa Rica

Abstract

Western flower thrips (WFT) [Frankliniella occidentalis (Pergande)] is a pest of greenhouse-grown floriculture crops worldwide. To determine if plant resistance varied in three populations of impatiens (Impatiens wallerana Hook. f.) collected near San Vito, Costa Rica, 59 genotypes were evaluated for resistance to feeding by WFT. Individual insect-free plants of each genotype were inoculated with 20 laboratory-reared WFT. Thrips were allowed to feed on individual plants for a 4-week period followed by visual evaluations to estimate feeding damage. Feeding damage varied among genotypes. Thirty-seven genotypes had feeding damage levels similar to the susceptible control, while 22 entries were significantly more resistant than the susceptible control. Of the 22 genotypes with some level of resistance, six genotypes were commercially acceptable, having mean visual ratings below 4.0 on a 1 to 9 evaluation scale. Five of these six genotypes were seedlings from a single population and represented 13.9% of the seedlings in that population. The remaining seedling was from a second San Vito population. The plants in these populations identified as having acceptable levels of damage may be useful in a breeding program designed to enhance resistance to WFT feeding damage. Because WFT feeding damage varied among genotypes, the potential for improving impatiens resistance to WFT exists within available germplasm.