THE BREAKUP OF INITIAL LINKAGE BLOCKS UNDER SELECTED MATING SYSTEMS

Abstract

The extent to which linkage blocks are broken and to which recombination occurs is of critical interest to the plant breeder since the success of his breeding program depends upon obtaining desirable genetic recombinations. The con- ventional procedure for the improvement of a self-pollinated species involves a program of continued crossing and pure lining. If the genetic diversity can bc maintained in the breeding material, effective breakup of linkage blocks and recombination of genetic types will be achieved over an extended period of time. Unfortunately, genetic diversity is not always maintained in the advanced breeding stock. Information on the extent to which linkage blocks can be broken if a gene pool were held in a heterozygous state for a selected number of generations and then pure lined would be extremely helpful in evaluating breeding procedures. The objective of this paper is to derive the average lengths of linkage blocks per chromosome which are intact after selected breeding procedures and to interpret the information available from a segment analysis. Mating systems involving random mating within a population synthesized from a limited number of parents and pure lining from such a random mating population will be considered in detail in this paper.