Statistical Genetics and Simulation Models in Genetic Resource Conservation and Regeneration

Abstract

A major objective when regenerating germplasm collections is to maintain as many genes (or alleles) as possible. Two stages, sampling and propagating, can be identified in any regeneration cycle. A rare allele can be lost at either stage, when a cross-pollinated population is being regenerated. The objectives of this study were (i) to derive the theoretical probability that one or a few rare alleles will be retained after one regeneration cycle and (ii) to determine, through computer simulation, the average number of alleles lost after a certain number of regeneration cycles. The effects of four mating methods commonly used on cross-pollinated crops (i.e., random pollen pollination, chain cross, paired cross, and self-pollination) were compared. If more than five seeds are harvested from each regenerated plant, the probability that an allele will be lost during Stage 2 can be ignored. However, harvesting and maintaining more seeds than are required for subsequent regeneration cycles will have some negative effects on the retention of genetic diversity. Self-pollination is the best mating strategy for retaining rare alleles only if the germination rate is 100% and all the reserved seeds are regenerated. It can be used for species where inbreeding depression is not serious and the seeds of individual plants from an accession can be stored separately. Paired cross without reciprocal is recommended for regenerating cross-pollinated species, as it results in the same genetic consequence as paired cross with reciprocal or chain cross, but requires only half the number of labor-intensive crosses.