Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/20/2007
Publication Date: 1/15/2008
Citation: Conaghan, P., Casler, M.D., O'Kiely, P., Dowley, L. 2008. Efficiency of indirect selection for dry matter yield based on fresh matter yield in lolium perenne l. sward plots. Crop Science. 48:127-133. Interpretive Summary: Breeding and evaluating new grass varieties for increased forage yield requires the evaluation of tens of thousands plots over a relatively short time span. This is further magnified by the need to harvest each plot many times over the duration of any particular trial. Determination of dry matter content of herbage on all plots is a severe limitation to the number of plots that can be evaluated. This study reports on the use of fresh-weight yields as a substitute for dry-matter yields, demonstrating a high correlation between the two yield measurements over a series of perennial ryegrass trials under two different management regimes. The results indicate that ryegrass breeders can improve dry-matter yields without measuring dry matter content on a routine basis. These results will be of value to other forage grass breeders.
Technical Abstract: Forage dry matter yield (DMY) is a high-priority trait in breeding perennial ryegrass (Lolium perenne L.). However, determining dry matter concentration is highly labor intensive. Indirect selection based on fresh matter yield (FMY) would be easier, quicker and less expensive and, for a similar level of resources, would allow a greater number of replicates, genotypes, or both, to be evaluated. Our objective was to determine the efficiency of indirect selection for DMY based on FMY in perennial ryegrass sward plots. Over a 14-year period, pure swards of perennial ryegrass sown at Oak Park Research Centre, Carlow, Ireland were assessed for DMY and FMY at each harvest over 2 consecutive years. Trials, containing genotypes of similar ploidy and maturity category, were subjected to either a frequent or infrequent cutting management program. Forage was generally surface dry when harvested. The efficiency of indirect selection based on two replicates and comparable selection intensity was high ( 0.80). Resources were utilized more efficiently by evaluating more genotypes than by increasing the number of replicates. For example, doubling the number of plots to increase the number of replicates from two to four increased the efficiency of indirect selection from a mean 0.88 to 0.94. However, doubling the number of plots and including more genotypes, facilitating greater selection intensity, increased the efficiency of indirect selection from a mean 0.88 to 1.04.