RESPONSE OF WHITE BEAN TO BACTERIAL-BLIGHT, OZONE, AND ANTIOXIDANT PROTECTION IN THE FIELD

An interaction between ozone and bacterial blight incited by Xanthomonas phaseoli on white beans (Phaseolus vulgaris 'Sanilac') was investigated in the field by reducing ozone injury with the antioxidant EDU (N-2-(2-oxo-1-imidazolidinyl)ethyl-N-phenylurea). Plants were inoculated with X. phaseoli at time of flowering and weekly sprays of EDU at 1 kg/ha were begun at the same time. Potentially phytotoxic concentration of ozone in excess of 8 pphm were recorded 11 times during the summer of 1977. Infection with X. phaseoli reduced symptoms of foliar ozone injury 19% on plants not treated with antioxidant but X, phaseoli did not protect against ozone injury on treated plants. Ozone injury did not protect against blight infection. Plants protected with EDU averaged 38% less ozone injury and became defoliated 3 wk later than control plants. Yields of EDU-protected plants increased 24% relative to unprotected controls. Weight of bean seeds was inversely correlated with per cent leaflet abscission, suggesting that increases in yield of EDU-protected white bean plants may have been due primarily to reduced defoliation rather than to reduce foliar injury.