Inflorescence Sampling Improves Effective Population Size of Grasses

Variation in seed production per plant leads to reductions in effective population size (N e ), which is a major factor promoting genetic drift of heterogenetic populations during seed collection and regeneration. The objectives of this study were (i) to compare N e to the census population size (N c ) among different seed harvest methods; (ii) use inflorescence sampling to determine N e /N c for numerous heterogenetic grass species, and (iii) to predict the optimum number of inflorescences per plant to most efficiently increase N e Estimates of N e /N c from rubbing whole plants, cutting whole plants, and from sampling a constant two inflorescences per plant were made on Festuca pratensis Huds., Lolium perenne L., and Pseudoroegneria spicata (Pursh) Á. Löve accessions. Inflorescence sampling was also completed on four accessions of Bromus inermis Leyss., Dactylis glomerata L., F arundinacea Schreb., L. perenne , Pseudoroegneria spicata , and Phalaris aquatica L. The mean N e /N c for the inflorescence method was 0.78, significantly higher then the 0.64 average for the cut or rub methods. For all species and entries, the slope of the curves describing N e /N c to inflorescence number was initially steep from 1 to 3 inflorescences and then leveled off asymptotically. Thus, most of the benefit occurs after sampling only a few inflorescences. The results show that sampling a constant number of inflorescences per plant promotes N e and reduces the potential for genetic drift associated with collection and regeneration of heterogenetic grass populations.