The Impact Of Increasing Surface Ozone Concentration On Grain Quality Of Rice (Oryza Sativa L.)

To investigate the effects of high ozone (O3) concentration on processing quality, appearance quality, cooking and eating quality and nutritional quality of different rice varieties, we conducted an experiment for the first time in the world with using Free Air ozone Concentration Enrichment (FACE) system at Xiaoji town, Jiangdu County, Jiangsu Province, China (119°42′0″E,32°35′5″N). Four rice cultivars, Wuyunjing21 (conventional japonica cultivar ), Yangdao6 (conventional indica cultivar), Shanyou63 (three-line hybrid rice cultivar), Liangyoupeijiu (two-line rice cultivar), were grown at ambient and elevated (target at 50% above ambient) ozone concentration. The results obtained here could provide important implications on rice breeding under future elevated O3 conditions. The main findings are as follows:1 On average, high [O3] significantly decreased the yield of brown rice, milled rice and head rice by 16%, 15% and 13%, respectively. There was a significant difference among rice cultivars in yield of brown rice, milled rice and head rice. There was a significant interaction between O3 and cultivars for the yield of brown rice, milled rice and head rice. The magnitude of reduction was much larger in hybrid Shanyou 63 (28%, 27% and 23%, respectively) than in inbred japonica Wuyunjing 21 (10%, 10% and 11%, respectively), inbred indica Yangdao 6 (6%, 6% and 20%, respectively) and inter-subspecific hybrid Liangyoupeijiu (14%, 12% and -4%, respectively).2. On average, high [O3] decreased brown rice rate by 0.2%, while increasing milled rice rate and head rice rate by 0.5% and 3.4%, respectively, all with no significance. There was a significant difference among rice cultivars in the rate of brown rice, milled rice and head rice. There was a significant interaction between O3 and cultivars for head rice rate, while no significant interaction for brown rice rate and milled rice rate.3. On average, high [O3] increased chalky grain percentage, chalkiness area and chalkiness degree by 6.1%, 2.2% and 5.7%, respectively. Among them, the effect of high [O3] on chalky grain percentage was significant. There was a significant difference among rice cultivars in chalky grain percentage, chalkiness area and chalkiness degree. There was no significant interaction between O3 and cultivars for chalky grain percentage, chalkiness area and chalkiness degree.4. On average, high [O3] increased amylose content and gel consistency by 3.9% and 5.3%, respectively, while decreasing the gelatinization temperature by 0.4%. Among them, the effect of high [O3] on amylose content was significant. There was a significant difference among rice cultivars in amylose content, gel consistency and gelatinization temperature. There was no significant interaction between O3 and cultivars for mylose content, gel consistency and gelatinization temperature.5. On average, high [O3] increased the content of protein, Fe, Zn, Ca and Mg of four cultivars by 7.0%, 21.7%, 0.8%, 6.3% and 8.8%, respectively, while decreasing the content of K, Cu and Mn by 0.3%, 5.2% and 2.5%, respectively. Among them, the effect of high [O3] on the content of protein and Mg was significant. There was a significant difference among rice cultivars in the content of protein, K, Cu, Fe, Zn, Ca, Mg and Mn. There was a significant interaction between O3 and cultivars for the content of protein, while no significant interaction for the content of K, Cu, Fe, Zn, Ca, Mg and Mn.6. On average, high [O3] decreased the accumulation of protein, K, Cu, Zn, Ca, Mg and Mn of four cultivars by 7.3%, 12.6%, 18.9%, 6.3%, 12.5%, 6.5%, 4.2% and 15.2%, respectively, while increasing the accumulation of Fe by 2.7%. Among them, the effect of high [O3] on the accumulation of protein and Zn was significant. There was a significant difference among rice cultivars in the accumulation of protein, K, Cu, Zn, Ca, Mg and Mn. There was no significant interaction between O3 and cultivars for the accumulation of protein, K, Cu, Zn, Ca, Mg and Mn.7. On average, high [O3] decreased the highest viscosity, hot paste viscosity, collapse value, cold adhesive and the average time for the highest viscosity of four rice cultivars by 4.15%, 4.52%, 3.65%, 1.44% and 0.24 %, respectively, while increasing the impairment value by 10.11%. There was a significant difference among rice cultivars in the highest viscosity, hot paste viscosity, collapse value, cold adhesive, impairment value and the average time for the highest viscosity. There was a significant interaction between O3 and cultivars for the highest viscosity, hot paste viscosity, cold adhesive and impairment value, while no significant interaction for collapse value and the average time for the highest viscosity.