Rate of genetic gain of persistence to grazing, dry matter and seed yield of white clover across 90 years of cultivar development

White clover is a major contributor of productivity and ecological services in pastures and rangelands worldwide. The advantages of including and maintaining white clover in a pasture are well documented. White clover breeding is important worldwide and is recognized as a priority in many countries with a pastoral-sector based livestock productivity system. Furthermore, white clover seed production is often viewed as an additional component of the pastoral sector and contributes significantly to its economy. Excluding the fundamental genetic constraints associated with an outcrossing reproductive biology and allopolyploidy, such as a slower accumulation of favorable additive alleles via multiple allelic configurations as well as a slower purging of unfavorable alleles due to high levels of heterozygosity further increases in genetic gain have faced multiple limitations in white clover breeding over the years -despite an active commercial breeding and science arena. Genomic selection has proven success in livestock breeding. As such, genomic selection programs can benefit from collecting and using historical data from previously developed populations to include into their training population data. 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 in public and private plant breeding programs across 17 countries. An experiment was conducted to evaluate forage yield across three locations in New Zealand. A seed yield trial was performed in 2017. Variance partitioning indicated that the percent variance attributable to genotype over total genotype plus the genotype by environment interaction was 57.5%. In general, cultivar performance in the Waikato (WAI) environment resulted in greater contributions to the genotype by environment interaction (GE) variance component than the Manawatu (MAN) and Canterbury (CBY) environments. Generally, CBY and MAN resulted in more similar environments than WAI across all seasons. Overall, a number of New Zealand cultivars released in 2000 were highly adapted to MAN and CBY as well as two cultivars from USA released in 1990 and 2000. 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 while 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 in or 0.032%.decade-1 on average, 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 lines resulted in a two-fold increase for white clover dry matter yield and a four fold increase in rates of gain for white clover sward content.