Resistance Screening Techniques for Major Insect and Mite Pests in Vegetable Crops

Abstract

Host plant resistance is an important component of the integrated pest management (IPM) strategies. However, it was not fully exploited for managing the most challenging insect and mite pests of vegetable crops in the tropics and subtropics. In our attempts to develop pest-resistant vegetable varieties, the World Vegetable Center (WorldVeg) has screened a vast germplasm for major pest species in vegetable crops in the past few decades. To achieve that, there is a need for more accurate and more efficient techniques to assess the resistance or susceptibility of vegetable germplasm. Resistance to borer, defoliators, and storage pests can be generally measured based on the percentage damage that they cause. However, resistance based on population size and pest life stages can be also assessed to understand antixenosis and antibiosis factors for some insects such as whiteflies, sweet-potato weevil, and bean flies. Since aphids occur in large numbers, scoring the population using a rating scale simplifies the screening methodology and enabled us to evaluate a large number of genotypes. Scoring based on damage scales has been found to be the most reliable method of screening for resistance against thrips, leafhoppers, and mites. These scores can be directly used for statistical analysis or converted to the area under the infestation pressure curve (AUIPC). Various statistical analyses including but not limited to analysis of variance (ANOVA) or an analysis based on mean (m) and standard deviation (sd) can be used to group the screened genotypes into various resistance and susceptible categories. In addition, the use of biophysical and biochemical traits for pest screening as well as its role for elucidating mechanisms of resistance will be discussed in this chapter.