Breeding for Resistance to Diseases and Insects

Abstract

The cultivation of resistant varieties has been recognized as the most effective, ideal and economical method of reducing crop losses (Stakman and Harrar 1957). The breeding for resistance is generally no way different than breeding for other traits. However, in resistance breeding the two biological entities, host plant and parasite, are involved, whereas in breeding for other traits the breeder deals with the variability in test material only. The first step in resistance breeding programmes is the collection of natural variability followed by finding out the sources of resistance. The information on these aspects has been described in detail in Chap. 5. The next step is to incorporate the resistance gene(s) from the donor parent(s) using various methods including induced mutations, where the susceptible alleles are altered by the use of mutagens. These methods are discussed in this chapter. In view of the dynamic nature of parasites, the resistant gene(s) fall susceptible after a few years or are no longer effective. Therefore, the resistance breeding programme is a continuous one. An attempt is also made in this chapter to describe how best the race-specific or non-specific genes may be managed so that the life span of resistant gene(s) is prolonged and also the disease losses are avoided or reduced.