ARS | Publication request: EFFECTIVE POPULATION SIZE REDUCTION ASSOCIATED WITH FECUNDITY VARIATION IN GRASSES

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 1, 2000
Publication Date: September 1, 2000
Citation: Johnson, R.C., Bradley, V.L. 2000. Effective population size reduction associated with fecundity variation in grasses. Crop Science. 42:286-290.

Interpretive Summary: Preserving plant genetic resources requires understanding sampling methods associated with the seed increase process. In the relatively small populations associated with seed increase, the potential for random genetic drift is a major concern. To reduce genetic drift the key parameter is the effective population size, the number of plants effectively mating, rather than census population. This work showed that substantial reductions in the effective population were associated with the variability in seed production of grass accessions. However, a substantial improvement in effective population size was observed by sampling two plant panicles or spikes per plant. This work indicates that this sampling procedure may be a way to reduce genetic drift without greatly increasing the cost of the seed increase process.

Technical Abstract: The variance effective population size (Ne) is the key parameter for predicting genetic drift associated with germplasm regeneration. A major factor reducing Ne below the census population (N) is variation in seed production per plant. The objective of this study was to estimate Ne/N resulting from variation in seed production in three wind pollinated grass species, each represented by three accessions grown at two locations. For one accession from each species, Ne/N was also estimated on inflorescence samples from each plant. The average Ne/N values for species differed at P<0.05, with values of 0.42, 0.51, and 0.63 for Lolium perenne, Festuca pratensis, and Pseudoroegneria spicata, respectively. For inflorescence samples, Ne/N was 59 percent higher than the corresponding seed per plant values, and averaged 0.69, 0.88, and 0.86 for L. perenne, F. pratensis, and P. spicata, respectively. The results showed substantial reductions in Ne associated with variation in seeds per plant, but a substantial improvement in Ne with inflorescence sampling.