Application of molecular marker assayed paternity in a white clover breeding program

Abstract

The use of molecular tools, coupled with improvements in paternity assignment computation, offer breeders a cost-effective and readily implementable breeding tool to improve the rate of genetic gain in forages. Molecular marker paternity assays may improve genetic gain in white clover (Trifolium repens L.) half-sib family breeding programs by utilizing a larger coefficient of additive genetic variation. To evaluate the potential to improve breeding outcomes by use of a molecular marker paternity assay in allotetraploid white clover (2n = 4x = 32), seven single-locus, homoeologue-specific simple sequence repeat markers were genotyped and analyzed on 1277 half-sib progeny and their 20 parents from a polycross pollinated by bumble bees (Bombus sp.). Paternity was assigned to 88.9% of progeny using a likelihood algorithm implemented in Cervus. Estimates of additive genetic variances from multisite, space-planted field experiments established in perennial ryegrass (Lolium perenne L.) were used to predict selection responses. Joint maternal and molecular-marker-assayed paternal half-sib family selection offered improved theoretical selection gains relative to conventional maternal half-sib family selection for herbage yield and trifoliate center leaflet width. The estimated selection responses based on empirical parameters demonstrated the theoretical wisdom of incorporating molecular-marker-assayed paternity in white clover breeding programs as an effective tool to improve selection responses per cycle of selection.