OZONE TOLERANCES OF SOYBEAN CULTIVARS AND NEAR-ISOGENIC LINES IN A FUMIGATION CHAMBER

Ozone (O3) toxicity is a potential yield-limiting factor for soybean ( Glycine max L. Merr.) in the United States and worldwide. The most eco nomical solution to the problem is to use Os-tolerant cultivars. Thirt y-four cultivars and 87 near-isogenic lines (NILS) of soybean were scr eened for O3 tolerance in a fumigation chamber (250 ppb for three hrs) . Most tolerant cultivars tested were 'Cloud', 'T-276', 'T263', and 'K indu'. Moderately tolerant cultivars included 'Davis', 'T-210', and 'E lton'. Most sensitive cultivars were 'Corsoy 79', 'Noir', and 'Midwest '. The original 'Clark' cultivar was not tested, but 'Clark 63' tended to be more tolerant than 'Harosoy'. The aluminum (All-tolerant 'Perry ' cultivar also tended toward greater O3 tolerance than the Al-sensiti ve 'Chief', as observed earlier. Our rankings of 'Hark' as moderately sensitive and 'Davis' as moderately tolerant are also in agreement wit h earlier reports. Among NILS, the order of O3 tolerance was generally Williams>Clark>Harosoy, but differences were also observed within the se parental groups. For example, L68-560 was more tolerant than some o ther NILS of 'Harosoy'. 'L76-1988' appeared more tolerant to O3 than o ther NILS of 'Williams', but all 'Williams' NILS were more tolerant th an most NILS of 'Harosoy' and 'Clark'. Ozone-tolerant and -sensitive s oybean cultivars or NILS identified in our study may be useful tools i n studies on mechanisms of O3 tolerance and differential O3 tolerances in plants and in the development of ameliorative measures.