Isolation Distance, Inflorescence Sampling, and Population Size: Maintaining Genetic Diversity in the U. S. Temperate Grass Germplasm Collection.

摘要

During the regeneration of cross -pollinating accessions, genetic contamination from foreign pollen and reduction of the effective population size can be a hindrance to maintaining the genetic diversity in the temperate grass collection at the Western Regional Plant Introduction Station (WRPIS). These problems have been addressed in several studies by researchers at the WRPIS. Genetic contamination by windborne pollen was studied using pubescent and glabrous smooth bromegrass (Bromus inermis Leyss.) strains. This study indicated that an isolation distance of 22 to 27 m results in a relatively low level of pollen contamination between accessions of the same species. Other studies focused on how sampling methods affect genetic structure, development, and morphology in three model annual ryegrass (Lolium multiflorum Lam.) accessions over three regeneration cycles. Results showed that although harvesting the same number of seeds from each plant within an accession (balanced sample) is the most desirable harvest method, sampling a constant number of inflorescences (spike sample) from each plant improves the ratio of the effective population to the census population in a regeneration plot. Combining seeds proportionally according to seeds per plant (bulk sampling) was the least desirable harvest method. A fourth study used three perennial grass species to predict the optimum number of inflorescences to harvest per plant to reduce the potential for genetic drift within an accession. Using these research findings as a guide;germplasm managers at the WRPIS have revised the methods used in regenerating the U.S. temperate grass collection.