Plant Breeding

pp 391-406

Population Improvement Strategies for Crop Improvement

  • S. K. VasalAffiliated withInternational Maize and Wheat Improvement Center (CIMMYT)
  • , N. N. SinghAffiliated withIndian Agricultural Research Institute
  • , B. S. DhillonAffiliated withNational Bureau of Plant Genetic Resources
  • , S. J. PatilAffiliated withUniversity of Agricultural Sciences

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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.