Field resistance in Trifolium subterraneum to Uromyces trifolii-repentis and Cercospora zebrina

Abstract

Advanced, early-midseason breeding lines and overseas introductions of Trifolium subterraneum var. subterraneum and var. yanninicum were screened for resistance to rust (Uromyces trifolii-repentis) and cercospora (Cercospora zebrina) diseases in field 'miniswards', and their performances compared with appropiate control varieties. The reaction to each disease varied between genotypes. The most rust-resistant within var. subterraneum were CPI 89848D, CPI 89840A, and 76S40-6, all with final incidence scores of <5.5 on a 0-10 scale (0, no disease; 10, >90% leaves affected). On the basis of rust-induced leaf collapse, CPI 89848D, 76840-6, CPI 89838G, CPI 89840A, Areces 1, and B x D 15A Black-8 were the most resistant of var. subterraneum, with scores of 0-0.5 on a 0-5 scale. Except for CPI 39314YB, var. yanninicum was very resistant to rust, with rust incidence scores of 0.6-3. Lines 76Y51-31, 76Y52-3, 76Y51-28.2, and 76Y51-25 had the best resistance, with end-of-season incidence scores of 0.6-1.4. Except for 76Y51-27, there was no leaf collapse from rust in var. yanninicum. For cercospora disease, the most resistant lines within var. subterraneum were CPI 89838G, 75811-7, 76340-6, and CPI 89841E, with final incidence scores 51.5 on a 0-10 scale. Except for CPI 39314YB, var. yanninicum showed excellent resistance to cercospora disease, with end-of-season incidence scores 0.1-1.