Studies On Cold Tolerance In Chaling Wild Rice (Oryza Rufipogon Griff.) At Seedling Stage

It is helpful to study the physiological and biochemical mechanism underlying cold tolerance in wild rice in order to keep the grain yield and quality of rice cultivars by take effective measures as breeding and cultivation.To elucidate the physiological mechanism of cold tolerance in in Chaling wild rice(O.rufipogon Griff.),several rice cultivars(O.sativa L.) of differential cold tolerance and Dongxiang wild rice was taken as controls.The results were as follows:Under the stress of natural low temperature at seedling stage(March, 2008),the survival rate of Chaling wild rice was higher than that of 93-11,Guangzhouluai4,Liangyoupeijiu,Qiuguang,Taibei 309,and Nipponbare while lower than that of Dongxiang wild rice.Treatment with 11℃(light)/6(Dark)℃for 7 d at seedling stage,the survival rate was higher in Chaling wild rice than in 93-11,Guangzhouluai4, Liangyoupeijiu,Taibei 309 and Qiuguang,while lower than in Nipponbare and Dongxiang wild rice.Furthermore,during the period of low temperature treatment,the increasing extent of the activity of superoxide dismutase(SOD),peroxidase(POD),catalase(CAT) was higher in Chaling wild rice than in 93-11,Liangyoupeijiu & Taibei 309, while lower than in Nipponbare.The increasing extent of the content of ascorbic acid(AsA),glutathione(GSH) & soluble protein was higher in Chaling wild rice than in rice cultivars controls.The increasing extent of the electrolyte leakage & producing velocity of O₂^- and the content of malondialdehyde(MDA) & Proline was higher in Chaling wild rice than in Nipponbare & Taibei 309,while lower than in 93-11 & Liangyoupeijiu.The optimal/maximal quantum yield of PSâ…¡(Fv/Fm) was decreased slightly in Chaling wild rice,Nipponbare & Taibei 309, while decreased seriously in 93-11 and Liangyoupeijiu.Then followed by a recovery period of 4 days,the activity of superoxide dismutase, peroxidase,catalase and the content of ascorbic acid,glutathione,soluble protein & Proline was higher in Chaling wild rice than in 93-11 & Liangyoupeijiu,while no significant difference with Nipponbare & Taibei 309.The electrolyte leakage,producing velocity of O₂^- and the content of malondialdehyde was significantly lower in Chaling wild rice than those in 93-11 & Liangyoupeijiu,no significant difference with Taibei 309,but higher than those in Nipponbare,.The optimal/maximal quantum yield of PSâ…¡(Fv/ Fm) Chaling wild rice recovered to the normal level rapidly in Chaling wild rice than in Taibei 309,93-11 & Liangyoupeijiu,while near in Nipponbare.Based on above results,it is concluded that the chilly-tolerance of Chaling wild rice is closely relative to its antioxidant system.Moreover,rapid respones & stronger recovery capability to chilling stress were important characteristics of the chilling tolerance of Chaling wild rice.