Genotypic Variation for Morphological Traits in a White Clover Mapping Population Evaluated Across Two Environments and Three Years

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.) F 1 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 x year interaction for most of the morphological traits and mean seasonal growth. There was also significant (P < 0.05) genotype x environment x year interaction for some traits. The significant and large genotype x 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.