A Journey from the Field to the Functional Domains

Subterranean clover (Trifolium subterraneum L.) is the key forage pasture legume species in Australia and is also an ideal reference species for comparative mapping within the Leguminosae. It is a diploid (2n =16), predominantly inbreeding annual species that can be readily hybridised. It also has a wide range of diversity for both qualitative and quantitative agronomic and morphological characters. Subterranean clover displays distinctive markings on its leaflets, which together with other morphological characters such as anthocyanin pigmentation of calyces and stipules, and hairiness of leaves, stems and petioles, are used in seed certification to identify and distinguish between registered cultivars. The inheritance of leaf marks is well studied and the trait is largely controlled by multiple alleles at a single locus.

Our study identifies regions of the genome, which explain 87% of the leaf mark variation in a segregating population from a bi-parental cross in subterranean clover. In the population studied the leaf marks segregated in classic Mendelian ratio, indicating control by a single locus. However, studies on the inheritance of several leaf markings by Tan and Collins (1987) indicated that a high proportion of crosses did not conform to Mendelian segregation, leading to their suggestion that genetic control of this phenotype is complex.

The present analysis seeks to clarify the nature of the locus at the genome sequence level and demonstrate the feasibility of selecting for haplotypes of alleles within suites of genes associated with leaf marks.