Effect of clover root weevil larval feeding on growth of clover progenies from parents selected for tolerance in field trials

The effects of larval herbivory by clover root weevil (CRW, Sitona lepidus) on seven white clover (Trifolium repens) and two red clover (Trifolium pratense) progenies from plants showing tolerance of CRW in field trials were tested in two controlled glasshouse experiments. CRW larvae recovered from red clover plants were, on average, fewer (6.3 larvae/g root dry weight) and shorter (5.7 mm/g root dry weight) than those from white clover (16.7 larvae, 7.1 mm length).This confirmed previous findings that red clover is an inferior host for this pest. In the first experiment, progeny of four of the white clover selections for CRW tolerance showed high tolerance (shoot dry weights −2.9% to +3.1% different from their respective weevil-free controls) compared with a 13–24% shoot weight loss for two white clover cultivars. These results confirm field trial observations that there is variation for CRW tolerance in white clover and also that CRW tolerance is hereditable in at least some populations. The se...