Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2003
Publication Date: 7/1/2004
Citation: Johnson, R.C., Bradley, V.L., Evans, M.A. 2004. Inflorescence sampling improves effective population size of grasses. Crop Science. v. 44. p. 1450-1455. Interpretive Summary: Seed sampling methods that enhance effective population size will help maintain the diversity of heterogenetic populations during seed regeneration. We found in heterogenetic grass populations, sampling a constant number of inflorescences from each plant enhanced effective population size compared to combining all the seeds from each plant. Most of the benefit was derived when only three to five inflorescences were sampled. Inflorescence sampling appears to be a cost effective method to help maximize effective population size and diversity of heterogenetic populations during seed regeneration, thereby better maintaining the genetic integrity of samples. Potential applications include seed regeneration at gene banks, field germplasm collection, and in selection programs, when maintaining population diversity is desired.
Technical Abstract: Variation in seed production per plant leads to reductions in effective population size (Ne) and is a major factor promoting genetic drift of heterogenetic populations during seed regeneration. The objectives of this study were to 1) compare Ne to the census population size (Nc) among rubbing, cutting, and inflorescence sampling harvest methods, 2) to determine Ne/Nc for inflorescence sampling among numerous grass species, and 3) to understand the relationship between the number of inflorescences per plant and Ne/Nc. Estimates of Ne/Nc from rubbing whole plants, cutting whole plants, and from sampling two inflorescences per plant were made on Festuca pratensis (W6 17784), Lolium perenne (W6 9344), and Pseudoroegneria spicata (PI 236681) at Pullman and Central Ferry WA locations. Inflorescence sampling was also completed on four accessions of Bromus inermis, Dactylis glomerata, Festuca arundinacea, L. perenne, P. spicata, and Phalaris aquatica growing in existing regeneration nurseries at both locations. Although the location X entry interaction was significant, the mean Ne/Nc for the cut and rub methods averaged 0.64, and did not differ significantly. The mean for the inflorescence method was 0.78 and significantly higher then cut or rub methods. For the six species, the average Ne/Nc was also 0.78, and differences among species or locations were not observed. For all entries studied, the slope of the curves describing Ne/Nc to inflorescence number was initially steep from 1 to 3 inflorescences and then leveled off asymptotically. The results show that a constant number of inflorescences per plant will improve Ne/Nc compared to whole plant methods, and most of the positive effect can be derived after relatively few inflorescences per plant are sampled. Inflorescence sampling is therefore recommended as a method to promote Ne and reduce the potential for genetic drift during regeneration of heterogenetic populations.