proved white clover in paddocks (Pederson and Brink, 2000). White clover (Trifolium repens L.) exhibits complex inheritanceSeed yield is a complex character showing continuof seed production potential. Genome maps allow plant breeders to ously distributed values, typical of multigenic control dissect the genetic control of complex traits into discreet factors with with environmental influences on trait expression. Sev-Mendelian inheritance, each of which is called a quantitative trait locus (QTL). A pair-cross between two highly heterozygous white eral component traits influence SY in white clover. Seed clover genotypes created an F 1 mapping population (n ϭ 182) used to yield is the product of ID and YI. Yield per inflorescence investigate the genetic control of seed yield (SY) and three component is itself a product of variation in seed size and density traits: inflorescence density (ID), yield per inflorescence (YI), and (measured as TSW), floret number per inflorescence, thousand-seed weight (TSW). Analysis of 3 yr of field data from a and floret fertility. The use of increased YI rather than replicated trial in the primary seed production region of New Zealand increased ID may be a preferred strategy to boost SY indicated no strong correlations among the component traits. The in white clover. Each inflorescence is at the cost of ANOVA indicated significant genotype, year, and genotype ϫ year a stolon, suggesting that types with high inflorescence effects for SY, ID, and YI; and genotype and genotype ϫ year effects numbers will have compromised on-farm persistence. for TSW. Using genotype data for 209 microsatellite loci in the allo-The balance between SY potential and forage perfortetraploid genome, the multiple QTL model analysis resulted in the mance potential is yet to be clearly defined. Annicchiardiscovery of 23 QTLs related to seed production in white clover. ico and colleagues (Annicchiarico et al., 1999) report a Both parent plants harbored beneficial alleles for SY and the three component traits. A region of the genome at the distal end of linkage

Two recently released white clover cultivars, Grasslands Kopu II and Crusader, were compared with existing cultivars for at least 3 years in each of five field trials under rotational grazing by either dairy cows or sheep in the Waikato and Manawatu. Kopu II, a large-leaved cultivar with intermediate cyanogenesis and high stolon density relative to its leaf size, performed strongly under dairy grazing with high clover yields in summer, autumn and winter, and improved persistence in year 3 of these trials. Kopu II, along with Kopu and Sustain, also had high soluble carbohydrate content. Crusader is comparable to Huia in leaf size, but has higher cyanogenesis and stolon density than Huia. Crusader outperformed all other cultivars under sheep grazing with high clover yields in autumn, winter and spring. Under dairy grazing, Crusader performed very well in years 1 and 2 but did not perform as well as Kopu II in year 3. Both of these cultivars have performed well in international testing with Kopu II having high yield and stolon density under cattle grazing in Northern USA, while Crusader has been nationally listed in the UK based on NIAB trial results. Kopu II and Crusader represent the first of a new generation of white clover cultivars bred to perform well in both national and international markets. Keywords: breeding, cultivar, dairy, sheep, Trifolium repens, white clover

Grasslands Tribute is a medium-large leaved white clover released in 2003. It was initially bred for drought tolerance and winter activity in Victor ia, Australia from crosses among elite New Zealand germplasm. Tr ibute was then screened for agronomic performance in New Zealand and reselected for medium-large leaf size, uniform flowering pattern, absence of foliar disease and high seed yield potential. Almost half of the 11 parental lines of Tribute came from half-sib families based on a Syrian accession with the remaining half-sibs based on Sustain, Southern Europe II and Crau in approximately equal proportions. The decision to release Tribute was based on its consistent performance and persistence under grazing in a series of seven New Zealand trials. Tribute was the best medium-large leaved variety under both sheep and dairy grazing, with only the large-leaved Kopu II having better performance under dairying. It shows strong growth in all seasons but has very good coolseason growth, and good drought tolerance in Canterbury. Keywords: breeding, cultivars, dairy, sheep, Trifolium repens, white clover

Genetic gain from phenotypic selection in open-pollinated forage species is constrained by the inability to accurately use phenotype to estimate genotype, prior to parent selection for polycrossing. The use of marker-assisted selection (MAS) offers the potential to accelerate genetic gain by partially overcoming this constraint. White clover (Trifolium repens L., 2n = 4x = 32) is an open-pollinated, high-quality, perennial forage legume with complex inheritance of traits underpinning pasture persistence, seed production, animal productivity, and animal health. Our legume improvement programme has utilised seed production in white clover as a case study in the application of MAS in outbred forage species, using microsatellite markers linked to quantitative trait loci (QTL) of moderate resolution. The QTL SY03-D2 on the distal end of group D2, was used to explore marker:trait associations in 12 breeding pools, leading to opportunities to conduct reselection experiments, and to monitor response to genotypic selection criteria in experimental polycrosses. Each breeding pool was sampled with 90 or more individuals grown out in an unreplicated field trial to assess seed yield traits, as per standard practice in our cultivar development programme. DNA samples were tested with up to three microsatellite markers associated with the QTL. Significant (p < 0.01) marker:trait associations were observed in 8 of the 12 breeding pools, with the most informative polymorphisms accounting for differences of 30-69% in the mean seed yield values within breeding pools. These data suggest that value can be realised from the current investment in genomics for MAS in white clover, given QTL of moderate resolution, and widely used marker platforms such as microsatellites.

Phenotypic measurements of plants growing in swards are often confounded by a combination of environmental variation and experimental error. Genetic analysis allows plant scientists to decipher genomic regulation control of key traits, informing breeding strategies and enabling marker‐aided breeding. Our research objective was to estimate genotypic variation for a range of key aboveground morphological traits in a white clover (Trifolium repens L.) F1 mapping population evaluated over 3 yr across two contrasting New Zealand environments in mixed sward conditions. Significant (P < 0.05) genotypic variation for internode length, node number, stolon branching, and stolon thickness was observed, both within individual environments and also across environments and years. There was also significant (P < 0.05) genotypic variation within the population for herbage growth within seasons and across years at the Palmerston North site, which was related to the morphological characters. The potential genetic variation was also characterized by repeatability estimated within individual environments and across environments and years. Analysis of progeny performance across years within a site indicated significant (P < 0.05) genotype × year interaction for most of the morphological traits and mean seasonal growth. There was also significant (P < 0.05) genotype × environment × year interaction for some traits. The significant and large genotype × environment interactions emphasized the importance of trials conducted across multiple environments and years in perennials such as white clover. Genotypes with positive correlation between herbage growth and stolon branching, a trait associated with vegetative persistence, were identified. An interesting observation was the range of diverse phenotypes within the population, the result of a simple pair cross between two morphologically and genetically distinct parents. When extended to include a marker analysis, these trait data will provide for a more thorough understanding of the genetic architecture and control of these pivotal economic traits in white clover and their response to change in environment.