Rate of Genetic Gain for Persistence to Grazing and Dry Matter Yield in White Clover across 90 Years of Cultivar Development

• Published in: Crop science Vol. 59; no. 2; pp. 537 - 552
• Main Authors: Hoyos-Villegas, V., O'Connor, J. R., Heslop, A. D., Hilditch, A., Jahufer, M. Z. Z., Barrett, B. A.
• Format: Journal Article
• Language: English
• Published: The Crop Science Society of America, Inc 01-03-2019
• ISSN: 0011-183X; 1435-0653
• DOI: 10.2135/cropsci2018.07.0471

White clover (Trifolium repens L.) is a major contributor of productivity and ecological services in pastures and rangelands worldwide. White clover breeding is recognized as a priority in many countries with a pastoral‐based livestock productivity system. The objective of this study was to provide an updated estimate of the rate of change in genotypic value attributable to population improvement in white clover, using a set of 80 cultivars released between 1920 and 2010 by public and private plant breeding programs across 17 countries, in an experiment to evaluate forage yield across three locations in New Zealand. Overall, some New Zealand cultivars released in the 2000s were highly adapted to more stable testing environments. Geographic origin resulted in differential rates of gain. A segmental regression comparing the pre‐1965 and post‐1965 rates of gain was performed. The pre‐1965 regression line for white clover dry matter yield resulted in an absolute rate of increase of 0.031 g m−2 yr−1 decade−1 or 0.087% decade−1, whereas the post‐1965 line resulted in an absolute rate of increase of 0.058 g m−2 yr−1 decade−1 or 0.162% decade−1. White clover content resulted in a pre‐1965 absolute rate of increase of 0.011% content decade−1 or 0.032% decade−1 on average, and the post‐1965 line indicated an absolute rate of increase of 0.04% content decade−1 or 0.121% decade−1 on average. The comparisons between pre‐1965 and post‐1965 indicated a twofold increase for white clover dry matter yield and a fourfold increase in rates of gain for white clover sward content since 1965; however, the rate of gain remains below the theoretical potential.