Plant Breeding Methods for Drought Resistance
Breeding methods for drought resistance are the same as for yield and other economic characters. Breeding for drought resistance refers to breeding for yield under soil moisture stress condition. In other words, it refers to yield improvement in environment represented b water deficit. Four breeding methods, viz. 1) Introduction, 2) Selection, 3) Hybridization, 4) Mutations are commonly used for development of drought resistant crop cultivars.
In self pollinated crops, introduction, pure line selection, mass selection, hybridization (Pedigree method and backcrossing) and mutation breeding are used. When drought resistance is available in an exotic variety, such variety can be introduced and after through testing, if found suitable, can be released in the new area. When the drought resistant genotypes are available in the land races or mixed populations, either pure line selection or mass selection is adopted. When the resistant genes are available in the germplasm or wild species, the breeder has to resort to hybridization. Mutation is used when the desired genes are not available in the germplasm. Sufficiently large segregating populations have to be grown to select for drought resistance. In maize, drought tolerance is controlled by no less than genes pairs. Simple screening was effective in selection of drought resistant characters in one genotype, screening of material under drought conditions, use of large population in yield test and testing at several locations will help in selection of superior lines.
In cross pollinated crops, the most commonly used methods are mass selection, backcross , hybridization of inbreds to develop hybrid cultivars, recurrent selection and formation of synthetic cultivars. Mass selection is partially effective because there is no control of pollination. The backcross method is equally successful in self and cross pollinated species. Heterosis is used in both species. However, hybrid vigour is more successful in cross pollinated species than in self pollinated ones.