White clover vegetative persistence under pressure: sharpening New Zealand's competitive edge

Abstract

White clover is relied upon as a cornerstone of the international competiveness of New Zealand's pastoral sector, despite its vegetative persistence and yield being constrained by pests and diseases. The species' vulnerability has been highlighted by the clover root weevil (Sitona lepidus) incursion, and the impact of increased residual pest and pathogen loadings under minimum tillage techniques. Plant breeding with a focus on plant health has made improvements in white clover performance, and there is scope to develop varieties that ensure a more resilient legume component in pastures. An exemplar outcome from this approach is improved vegetative persistence and dry matter yield under nematode and clover root weevil pressure, as shown in field trials of elite breeding material. An enhanced, unified plant breeding and plant health approach can increase the performance and vegetative persistence of white clover. Trait selections to increase resilience and dry matter yield include optimum root architecture; single and multi-gene resistance or tolerance mechanisms; multi-pest defence compounds; and symbiont:clover combinations enabling induced pest and disease resistance. Cost effective and timely plant health assays for plant breeding are essential. Improved breeding strategies will create value on-farm via perennial forage legumes that perform better under pressure from pests. Keywords: white clover, plant breeding, plant genetics, nematode, pest resistance, pest tolerance