QTL ANALYSIS OF MORPHOGENETIC AND DEVELOPMENTAL TRAITS IN AN SSR-BASED GENETIC MAP OF WHITE CLOVER (Trifolium repens L.)

¹ Legume Breeding and Genetics, Institute of Grassland and Environmental Research, Plas Gogerddan, Aberystwyth, Ceredigion, SY 23 3EB, UK

² Plant Biotechnology Centre, Primary Industries Research Victoria, La trobe University, Bundoora,Victoria 3086,Australia

³ Pastoral and Veterinary Institute,Primary Industries Research Victoria,Mount Napier Road, Hamilton, Victoria 3300, Australia

⁴ Crop Genetics, Pioneer hi-bred International,7300 NW 62nd Avenue,Johnston, Iowa 50131-1004, USA

White clover (Trifolium repens L.) is a key component legume of temperate pasture agriculture, and is an important target for molecular marker-assisted plant breeding. The first framework genetic linkage map of white clover has been constructed using a progeny set (F2[I.4R x I.5J]) derived from the intercross of fourth and fifth generation inbred genotypes carrying a self-fertile mutation (Sf). White clover simple sequence repeat (TRSSR) and amplified fragment length polymorphism (AFLP) markers were used to derive a map with 135 markers (78 TRSSR loci and 57 AFLP loci) assigned to 18 linkage groups with a total map length of 825 cM. Sixteen of these linkage groups are presumed to correspond to the 16 chromosomes of the white clover karyotype. The F2(I.4R x I.5J) family has been subjected to intensive phenotypic analysis for a range of morphogenetic and developmental traits such as leaf area, internode length, plant height, plant spread, flowering date, floral intensity and seed yield, with both spatial and temporal replication. The data has been analysed to determine the trait heritability values and correlation coefficients between characters, and QTL analysis has been performed using single marker regression (SMR), interval mapping (IM) and composite interval mapping (CIM) techniques. QTLs were detected for the majority of traits, and the locations and magnitudes of QTL effects were compared across replications. This first genetic dissection study of agronomic traits in white clover provides the basis for comparative studies in more complex populations and the design of marker-assisted selection strategies.