Differential Responses of Four Bean Cultivars to Chronic Doses of Ozone

Abstract

Abstract Four cultivars of bean ( Phaseolus vulgaris L.), with different sensitivities to ozone (O 3 ), were exposed to chronic doses of O 3 for 7 hr/day in early and late-season studies. Plants were pot-cultured in open-top field chambers. Greater than ambient O 3 doses were applied by supplementing the O 3 present in nonfiltered air with additional O 3 at a constant rate for 7 hr/day. Cultivar sensitivity, as determined using an acute exposure screening protocol, was maintained in both studies. Regression of yield against O 3 concentrations showed that ‘BBL-254’ and ‘BBL-290’ were more sensitive to O 3 than were ‘BBL-274’ and ‘Dwarf Horticultural’. Results suggest that the acute screen used can predict the relative yield response of cultivars grown under field conditions when very sensitive and very resistant cultivars are compared. The results support the contention that bean germplasm has traits for resistance to O 3 at current levels of O 3 , but that resistance is lost with increasing O 3 concentration. Predicted relative yield suppression at a 7 hr/day seasonal mean of 0.04 to 0.06 ppm (the common ambient range in eastern United States) was 2% to 4% for the two resistant cultivars and 10% to 26% for the two sensitive cultivars.