RESISTANCE AND ASSOCIATED YIELD LOSSES FROM RUST (UROMYCES-TRIFOLII-REPENTIS LIRO) IN MIDSEASON CULTIVARS OF TRIFOLIUM-SUBTERRANEUM L VAR SUBTERRANEUM L AND VAR YANNINICUM KATZN-ET-MORLEY

A field study was conducted to quantify the effect of rust on the herbage production and seed yield of 4 new midseason cultivars of Trifolium subterraneum (Denmark, Gosse, Goulburn, Leura) and to compare their performance with 8 current commercial cultivars. Leura, Gosse, and Goulburn were all resistant to rust, with Leura most resistant. Denmark was not resistant to rust, but was much less susceptible than Green Range and marginally less susceptible than Mt Barker. By the end of the season, rust had reduced herbage yield in Green Range, Junee, Karridale, and Seaton Park (32, 23, 22, 18%, respectively) but did not affect any new cultivar. Rust reduced the seed yields of all cultivars except Goulburn, Larisa, and Leura. Seed yields of Green Range, Woogenellup, Mt Barker, Seaton Park, Denmark, Esperance, Karridale, Gosse, and Junee were reduced by 75, 70, 58, 55, 49, 47, 40, 40, and 38%, respectively. Rust also reduced the size of seed in all cultivars except Goulburn.