Breeding white clover for tolerance to nematodes: overview of process and progress

Abstract

A base population of 80 cultivars or seedlines of white clover from around the world was used to develop nematode tolerant selections. Clover plants were grown in strips of black plastic, akin to strawberry growing, in order to increase soil temperature and thence nematode activity in clover roots. Clover growth was assessed visually and by dry matter determination in five rounds of selection from 1989-2001. After each round of selection the 20-30 best performing plants for each of three leaf sizes (large, medium and small) were polycrossed and the seed collected. The resulting selections have performed at least as well as, and in many cases better, than standard commercial cultivars at a range of field sites. Keywords: Meloidogyne, Heterodera, Pratylenchus, Trifolium, field selection, nematode tolerance, nematode resistance