Seed production trait associations and inheritance in interspecific hybrids between Trifolium repens (white clover) and Trifolium uniflorum

Trifolium repens L. (white clover) is an important component of temperate pastures, but its root morphology makes it vulnerable to drought and pest attack. T. uniflorum is a wild species, adapted to dry environments, with deep woody roots but poor vegetative growth and only 1-3 florets per inflorescence (head). Interspecific hybridisation to incorporate the drought tolerance and root characteristics of T. uniflorum into white clover led to primary hybrids (F-1 and BC1) with poor seed production. Advanced-generation hybrids expressed high variation for almost all seed-production traits, and seed production responded to selection. To inform future breeding programs, trait associations and heritabilities were analysed. Numbers of heads per plant, florets per head and seeds per floret were important factors with moderate-high heritabilities. The derived traits, numbers of seeds per head, florets per plant and seeds per plant, expressed low-moderate heritabilities. No negative associations between seed production and root traits were found in the hybrids, nor were there any negative associations among head production, persistence and foliage production. Selection for improved seed-production traits should be effective without adversely affecting vegetative traits.