Recurrent selection for seedling vigor in kura clover

Kura clover (Trifolium ambiguum M. Bieb.) is a rhizomatous perennial forage legume that has outstanding persistence once established. Low seedling vig or presents a challenge to kura clover establishment. Kura clover seedlings partition a significant portion of their dry matter to below ground growth . Therefore, seedling vigor could be improved by increasing dry matter allo cation to the shoot. Our objective was to study the potential of recurrent phenotypic selection in the greenhouse for reduced root/shoot ratio to incr ease seedling vigor. Three cycles of divergent selection for root/shoot rat io and a control selection for large plant biomass (LP) were performed from a parent population consisting of 'Rhizo', ARS-2678, KZ1, and Erect Spread er populations. Selections for low root/shoot ratio (LoRS) and high root/sh oot ratio (HiRS) were performed by independent culling after first selectin g for large total biomass. Parent and selected populations were evaluated i n the greenhouse and field. Three cycles of selection for LoRS and LP incre ased shoot yield in the field 42 d after planting (DAP) by 35 and 34%, resp ectively. Three cycles of selection for LoRS reduced root/shoot ratio in th e field by 16%. Selection for HiRS did not affect seedling size in the fiel d. Population mean shoot and total plant weights were correlated between gr eenhouse and field environments (average r = 0.89). Population mean seed we ight was correlated with shoot weight in the field (r = 0.68, P < 0.05). Th e results indicate that phenotypic greenhouse selection for seedling size i s an effective means of increasing seedling vigor in kura clover.