A COMPARISON OF SCREENING TECHNIQUES FOR RESISTANCE TO VERTICILLIUM WILT IN ALFALFA (MEDICAGO-SATIVA L)

Three screening tests for resistance to Verticillium wilt in alfalfa u sing stem cuttings were compared including: stem infusion with a funga l culture filtrate (SIF), leaf injection with a spore inoculum (LII) a nd stem infusion with a spore inoculum (SII). The disease severity ind ice (DSI) determined by the three tests were very similar on average a nd were significantly correlated for a population of 142 plants regene rated from tissue culture. The DSIs determined by the LII test were al so significantly correlated with the DSIs determined by the North Amer ican Standard test in a population of 20 Vertus (c.v.) plants. The res ults suggest that the assays using stem cuttings are effective for det ermining resistance to Verticillium wilt in alfalfa. Because they are nondestructive and quicker than the North American Standard test, thes e methods should find application in alfalfa breeding.