Seed Leakage Does Not Contribute to Thermoinhibition in Jalapeno and Cayenne Cultivars

Abstract

Chile (Capsicum annuum L.) seeds sown in July for fall transplants in the greenhouse often yield poor stands due to thermoinhibition. To determine cultivar response to high temperature, five jalapeno cultivars and one cayenne cultivar used commercially in Florida and New Mexico were tested. Two seedlots of `Cayenne, Large Red Thick', `Ole', `Jalapeno M', `Mitla', and `Tam Veracruz', and one seedlot of `Ebano' were evaluated on a thermogradient table at a temperature range of 20, 25, 30, 35, and 40°C. Percent germination, mean daily germination, and germination performance index were calculated. Additional seeds were soaked for 24 hours at 25, 30, 35, and 40°C. The exudate was then measured for electrical conductivity and glucose equivalents as an indication of seed leakage. All cultivars exhibited thermoinhibition, but the critical temperature of onset varied among cultivars. `Ebano' had the highest germination performance index across all temperatures among the six cultivars. At 40°C, however, no cultivar exceeded 4.0% germination. There was significant variation in germination performance between seedlots of some cultivars. The electrical conductivity and the number of glucose equivalents leached from the seed varied among cultivars, but did not correlate with decreased germination. Thermoinhibition in chile is probably due to factors other than those associated with membrane leakage.