Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/1/2002
Publication Date: 1/1/2002
Citation: Johnson, R.C., Bradley, V.L., Evans, M.A. Reductions in effective populations size during grass regeneration and improvements with sampling. Crop Science. 2002. v. 42. p. 286-290. Interpretive Summary: Seed grow-outs are normally needed to make genetic resources at gene-banks available for research and breeding. However, in genetically diverse material this process leads to the potential for genetic drift that can result in decreased genetic diversity. A loss in diversity results in fewer genes available for crop improvement. Our objectives were to measure the potential for genetic drift in grass germplasm during seed grow-outs and make cost effective recommendations to reduce the potential for genetic drift. The results showed a high potential for genetic drift in small regeneration populations normally used for grow-outs. Increased plant populations and harvesting a constant number of seed heads per plant are recommended as cost-effective methods to minimize genetic drift during seed grow-outs.
Technical Abstract: 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 size (Nc) is variation in seed production among plants in a given population. The objectives of this study were to estimate Ne/Nc associated with variation in seed production in three model wind pollinated, perennial grass species [Lolium perenne L., Festuca pratensis Huds., and Pseudoroegneria spicata (Pursh) Á. Löve], and to recommend cost effective sampling methodology to maximize Ne/Nc during seed regeneration. Three accessions of each species were grown at two field locations and variation in seed number among plants and mean seed production per plant used to estimate Ne/Nc. Mean seeds per whole plant, standard deviations, and Ne/Nc differed among species, and accessions within species (P<0.05). For whole plant samples, average Ne/Nc for each species differed with values of 0.42, 0.51, and 0.63 for L. perenne, F. pratensis, and P. spicata, respectively. However, average Ne/Nc based on two inflorescences per plant was 0.69, 0.88, and 0.86 for L. perenne, F. pratensis, and P. spicata, respectively, which was higher than that of whole plant samples. This higher Ne/Nc resulted from the elimination of the variation in inflorescence number per plant, a major source of variation in seed number among plants. The results showed the high potential for genetic drift in small regeneration populations. Increased plant populations and harvesting a constant number of inflorescences per plant are recommended as cost-effective methods to minimize genetic drift during regeneration of outcrossing grass germplasm.