Differential Responses of Four Bean Cultivars to Chronic Doses of Ozone

Abstract
Four cultivars of bean (Phaseolus vulgaris L.), with different sensitivities to ozone (O3), were exposed to chronic doses of O3 for 7 hr/day in early and late-season studies. Plants were pot-cultured in open-top field chambers. Greater than ambient O3 doses were applied by supplementing the O3 present in nonfiltered air with additional O3 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 O3 concentrations showed that ‘BBL-254’ and ‘BBL-290’ were more sensitive to O3 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 O3 at current levels of O3, but that resistance is lost with increasing O3 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.

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