Performance of North American and Australian lucernes in the Queensland subtropics. 1. Field reaction to important root and crown diseases

Abstract

Twenty-three lucernes from North America and five Australian lines were assessed for their sensitivity to root rot (Phytophthora megasperma f. sp. medicaginis), anthracnose/ crown rot (Colletotrichum trifolii) and root canker (Rhizoctonia solani). Plantings were spray irrigated or raingrown on sites representative of the major lucerne environments in southern Queensland. Ratings for each disease discriminated generally the same most susceptible and resistant lines across plantings, although significant sitexline interactions occurred, these being most pronounced for anthracnose. Nevertheless, mean ranking for reaction to each disease conformed to previous assessments conducted under more controlled conditions. For root rot, many of the North American lines showed resistances superior to those of the Australian lines Hunter River, Siro Peruvian and Paravivo, but not to Falkiner and HS Gen 3 Composite. None, however, were rated as having better resistance to anthracnose than Hunter River. Few of the introduced lines had better than moderate levels of combined resistance to root rot and anthracnose, a combination considered important for superior adaptation in the subtropics.