Interaction of cowpea with Phytophthora vignae: inheritance of resistance and production of phenylalanine ammonia-lyase as a resistance response

Abstract

The interactions between Phytophthora vignae and two cowpea cultivars are described. The cultivars are near-isogenic but differ in their resistance to P. vignae race 2. Cultivar Caloona is resistant, cv. Poona is susceptible. Resistance of cv. Caloona to race 2 is controlled by a single dominant gene and is expressed throughout the life of the plant in all tissues at temperatures up to 35°C. Inoculation of cut cowpea epicotyls with a plug of agar containing race 2 hyphae provides a reliable method of obtaining host tissue which responds in a predictable way to the pathogen. Phenylalanine ammonia-lyase (PAL) activity increases rapidly in invaded epicotyl tissue of cv. Caloona in response to i..