Identification of Tetranychus neocaledonicus (Acari: Tetranychidae) resistant genotypes in Phaseolus lunatus

Abstract

The spider mite Tetranychus neocaledonicus André (Acari: Tetranychidae) is a potential threat to the cultivation of lima bean (Phaseolus lunatus L.). In many countries, lima beans are grown by small-holder farmers with limited access to inputs and technologies. In such systems, the implementation of control practices, such as chemical treatments that require costly equipment and supplies, becomes unviable. Therefore, the development and use of resistant plant genotypes could provide a promising alternative for small producers. Accordingly, the present study aimed to identify and evaluate T. neocaledonicus-resistant genotypes of lima bean. A total of 30 lima bean genotypes were evaluated using the instantaneous increase rate (ri) of T. neocaledonicus reared on individual host genotypes, and T. neocaledonicus fertility life tables were generating by rearing mites on host genotypes with the two highest ri values (IFCE-085 and IFCE-091, considered highly susceptible) and two lowest ri values (IFCE-084 and IFCE-090, considered resistant). Only the IFCE-090 genotype adversely affected immature T. neocaledonicus individuals, by reducing their survival rate, net reproductive rate (Ro), finite rate of increase (λ), and intrinsic rate of increase (rm) and by increasing their mean generation time (T) and time to reach adulthood. The results demonstrate the variation in the susceptibility of lima bean genotypes to T. neocaledonicus and identify the IFCE-090 genotype as a potential source of mite resistance.