Seed-to-seedling transmission of Botrytis cinerea in chickpea and disinfestation of seed with moist heat

Chickpea crops in south-eastern Australia are affected in some seasons by poor emergence and seedling soft rot. Botrytis cinerea was isolated on a semi-selective agar medium from diseased seedlings and from samples of seed submitted by growers. The frequency of isolation from seed harvested in 1993-94 ranged from 0 to 95%. Higher isolation rates were associated with reductions in seedling establishment in 1994 estimated at 30-75%. Surface sterilisation studies showed that infection was largely external on the seed. In growth cabinet experiments at 8-18 degrees C, seedlings grown from infected seed or from seed inoculated with B. cinerea developed soft rot, and sporulation of the pathogen on the basal stem lesions was observed. Treatment of moist seed at 50 degrees C for 5 min or storage of seed at 20 degrees C for 12 months reduced the frequency of isolation of B. cinerea to 0 and 2%, respectively, with no adverse effect on germination. Heat treatment of freshly harvested seed reduced the isolation frequency from 98 to 18%. The applicability of heat treatment for seed disinfestation by chickpea growers is discussed.