OZONE TOLERANCE RELATED TO FLAVONOL GLYCOSIDE GENES IN SOYBEAN

Ozone toxicity can reduce soybean yields by an estimated 5 to 20%. The most economical and practical solution to the problem would be to use ozone-tolerant cultivars. Because ozone toxicity is an oxidative stre ss, one would expect that plants having higher concentrations and prop er kinds of antioxidants would be more tolerant. To test this hypothes is, 20 soybean lines or cultivars varying in contents of flavonol glyc osides (naturally occurring antioxidants) were tested for ozone tolera nce in a fumigation chamber and in phyto-toxic concentrations of ozone in ambient, unfiltered, air in a greenhouse. In general, ozone tolera nce was associated with the presence of kaempferol glycosides, particu larly K3 through K6 and K9. Lines containing no kaempferol glycosides (OX942 and OX281) were among the most sensitive to ozone stress. The K 9 compound has been associated with reduced numbers of stomata, drough t tolerance, and slower growth rates, and this could reduce ozone abso rption and toxicity, or K9 may be more effective in detoxifying ozone than other glycosides. Lee soybean was more tolerant to ozone and to m anganese (Mn) toxicity (also an oxidative stress) than Forrest. Cross tolerances of plant genotypes to these two stresses deserve additional study. Among cultivars compared, Mukden was ozone tolerant, Columbia and Harosoy were sensitive, and Blackhawk was moderately sensitive.