A series of rice somaclonal variants with photooxidation tolerance have been screened and preliminarily identified. It is indicated that somaclonal variants (regenerating plants) from calli of mature caryopsis of 0242...A series of rice somaclonal variants with photooxidation tolerance have been screened and preliminarily identified. It is indicated that somaclonal variants (regenerating plants) from calli of mature caryopsis of 02428 and Chugoku 91 which are tolerable to photooxidation are also tolerant and that those from 842, Meixuan Minghui 63-38, Meixuan Minghui 63-53, and Guichao 2 which are sensitive to photooxidation display a wide spectrum from sensitivity to tolerance under photooxidative condition, among them (168 variants) from 4 sensitive parents 2 variants (numbered as 93012, 93236) have strong ability and 17 variants have medium ability against photooxidation. Decline of net photosynthetic rates of these tolerant variants is remarkably less than that of sensitive variants under photooxidative condition. Moreover it is initially proved in posterities of some variants that this type of variation is of genetic stability. We suggest that rice somaclonal variants with photooxidation tolerance provide a new source of variation which could be used in breeding rice cultivars with higher photosynthetic efficiency in the near future.展开更多
Thirty genotypes from rice germplasm were identified under photooxidation and shading condition and divided into four basic types : (1) cultivars tolerant to both photooxidation and shading, (2) cultivars tolerant to...Thirty genotypes from rice germplasm were identified under photooxidation and shading condition and divided into four basic types : (1) cultivars tolerant to both photooxidation and shading, (2) cultivars tolerant to photooxidation but sensitive to shading, (3) cultivars tolerant to shading but sensitive to photooxidation, and (4) cultivars sensitive to photooxidation and shading. A comparative study of photosynthetic characteristics of a cultivar (cv. Wuyujing 3) that is tolerant and a cultivar (cv. Xiangxian) that is sensitive to both photoinhibition and shading showed that the photochemical efficiency of PSⅡ ( F v/F m ) and the content of PSⅡ_D1 protein in the tolerant cultivar “Wuyujing 3” decreased less under photoinhibition conditions as compared with “Xiangxian”. Under photooxidation conditions, superoxide dismutase was induced rapidly to a higher level and the active oxygen O - built up to a lower level in “Wuyujing 3” than in “Xiangxian”. At the same time, the photosynthetic rate decreased by 23% in “Wuyujing 3” vs. 64% in “Xiangxian”. Shading (20% natural light) during the booting stage caused only small decreases (7%-13%) in RuBisCO activity and the photosynthetic rate in “Wuyujing 3” but showed marked decreases (57%-64%) in “Xiangxian” which corresponded to the decreases in grain yield in the two cultivars (38% and 73%, respectively). The correlation analysis showed that the tolerance to photooxidation is mainly related to PSⅡ_D1 and that to shading is mainly related to RuBisCO activity. This study provided a simple and effective screening method and physiological basis for crop breeding in enhancing tolerance to both high and low radiation.展开更多
文摘A series of rice somaclonal variants with photooxidation tolerance have been screened and preliminarily identified. It is indicated that somaclonal variants (regenerating plants) from calli of mature caryopsis of 02428 and Chugoku 91 which are tolerable to photooxidation are also tolerant and that those from 842, Meixuan Minghui 63-38, Meixuan Minghui 63-53, and Guichao 2 which are sensitive to photooxidation display a wide spectrum from sensitivity to tolerance under photooxidative condition, among them (168 variants) from 4 sensitive parents 2 variants (numbered as 93012, 93236) have strong ability and 17 variants have medium ability against photooxidation. Decline of net photosynthetic rates of these tolerant variants is remarkably less than that of sensitive variants under photooxidative condition. Moreover it is initially proved in posterities of some variants that this type of variation is of genetic stability. We suggest that rice somaclonal variants with photooxidation tolerance provide a new source of variation which could be used in breeding rice cultivars with higher photosynthetic efficiency in the near future.
文摘Thirty genotypes from rice germplasm were identified under photooxidation and shading condition and divided into four basic types : (1) cultivars tolerant to both photooxidation and shading, (2) cultivars tolerant to photooxidation but sensitive to shading, (3) cultivars tolerant to shading but sensitive to photooxidation, and (4) cultivars sensitive to photooxidation and shading. A comparative study of photosynthetic characteristics of a cultivar (cv. Wuyujing 3) that is tolerant and a cultivar (cv. Xiangxian) that is sensitive to both photoinhibition and shading showed that the photochemical efficiency of PSⅡ ( F v/F m ) and the content of PSⅡ_D1 protein in the tolerant cultivar “Wuyujing 3” decreased less under photoinhibition conditions as compared with “Xiangxian”. Under photooxidation conditions, superoxide dismutase was induced rapidly to a higher level and the active oxygen O - built up to a lower level in “Wuyujing 3” than in “Xiangxian”. At the same time, the photosynthetic rate decreased by 23% in “Wuyujing 3” vs. 64% in “Xiangxian”. Shading (20% natural light) during the booting stage caused only small decreases (7%-13%) in RuBisCO activity and the photosynthetic rate in “Wuyujing 3” but showed marked decreases (57%-64%) in “Xiangxian” which corresponded to the decreases in grain yield in the two cultivars (38% and 73%, respectively). The correlation analysis showed that the tolerance to photooxidation is mainly related to PSⅡ_D1 and that to shading is mainly related to RuBisCO activity. This study provided a simple and effective screening method and physiological basis for crop breeding in enhancing tolerance to both high and low radiation.
