Population Improvement Strategies for Crop Improvement

Abstract

Recurrent selection is an important breeding method employed to improve the populations of crop plants particularly those of cross-pollinated species. It may be undertaken in one (intra-population improvement) or two populations (inter-population improvement) to upgrade the performance per se or combining ability. Intra-population improvement may involve evaluation of individuals (mass selection) or of progenies (full-sibs, half-sibs or selfed progeny selection) that have been developed within a population or test-cross progenies developed by using a tester (related or unrelated, narrow or broad-genetic base). Various methods of intra-population improvement aim at enhancement of the performance of the population per se, random mated or selfed generation , except that in case of test-cross progenies evaluation, the emphasis is on improving combining ability. Inter-population improvement involves simultaneous improvement of two heterotic populations with a focus on their combining ability. In inter-population improvement methods, also known as reciprocal recurrent selection, there are two important alternatives, based on the evaluation of half-sib or full-sib progenies developed by using the other heterotic population or inbred line from that as a tester. There are several possible modifications and additional features of various intra-and inter-population methods that can be incorporated to meet specific objectives of a programme. The integration of population improvement and hybrid research activities, and the improvement of traits related to stress have also been discussed. Introduction Breeding methods and selection strategies for improving populations in crop plants have developed and evolved continuously over the past sixty years. A few cross-pollinated plants such as maize have given a lead in developing new methodologies , which subsequently have been deployed in other crop plants. Practically, all the known breeding methods are flexible and can be modified appropriately to suit crop needs and tailored for