Changes In Physiological And Biochemistry And Differential Expressions Of Cold-resistance Genes In Wheat Under Low-temperature Stress In Spring

Spring frost in wheat is one of the most crucial meteorological factors in our country. Itwould affect the spike numbers, grain numbers and the seed weight directly, and would makea serious drop of the yield for wheat. Some areas which were injured by spring frost havemade the wheat yield dropped from30%to50%. So, it is more important to study the springfrost of wheat for ensuring the yield stably and highly. Our researches cultivated Huaimai20,Wanmai38, Xinong979, Aifeng3, Shanmai139, Zheng366, Xiaoyan22and Zhengmai9023with pots in field, and discussed the changes in physiological and biochemistry anddifferential expressions of cold-resistance genes in wheat under low-temperature stress inspring, important results are followed:1.After low temperature stress at anther connective phase, wheat heading stage havebeen delayed for2～4days. And, yield of per plant decreased significantly and by an averageof68.4%. Huaimai20, Wanmai38, Xinong979and Aifeng3have a small drop(﹤65%), andShanmai139, Zheng366, Xiaoyan22and Zhengmai9023have a larger drop(﹥70%). So,Huaimai20, Wanmai38, Xinong979and Aifeng3showed resistance in a better performance.Meanwhile, agronomic traits changes of wheat are differently. The plant height, long peduncle,haulm length under ear and spike formation probability has decreased, and the spike lengthhas slightly increased after low-temperature. Correlation analysis show that the spikes of perplant and grains of per spike are significantly (P≦0.01) positive related to yield, and there is asignificant (P≦0.05) negative relationship between haulm length under ear and seed weight.2. After low temperature stress at anther connective phase, the content of chlorophyll,malondialdehyde (MDA), proline and soluble protein, the activities of superoxide dismutase(SOD) and peroxidase (POD) in leaf are increased differently. Huaimai20, Wanmai38,Xinong979and Aifeng3have a smaller increase of MDA content than average (30.5%), and alarger increase of SOD, POD activities and chlorophyll, proline, soluble protein content thanaverage (5.0%,23.7%,17.3%,54.0%and16.2%, respectively). Their cytomembranes show alow degree of damage and a strong cold resistance. Under the low temperature stress,significantly negative correlations were observed in MDA content with other physiologicalindices, and the correlation coefficients ranged from-0.749(P≦0.05) to-0.883(P≦0.01);SOD, POD activities and chlorophyll, proline, soluble protein content show a significantly positive correlations with each other, the correlation coefficients ranged from0.798(P≦0.05)to0.963(P≦0.01). The gray relational grade analysis indicated that soluble protein, proline,chlorophyll content and SOD, POD activities have a higher relational grade and connectedclosely with the grain yield of per plant. Therefore, they are considered as important indices inthe selection of spring frost tolerance in wheat.3. In this study, the expression of ABA-independent cold-responsive (COR) genes(WCS120, WCS19and Wcor719) under low-temperature stress were analyzed by RT-PCR,then the relationships between gene expressions and wheat yield have been analyzed afterinvestigating in autumn. Results showed that the expression of WCS120, WCS19andWcor719in Shan229and Xinong979were higher than that of another two cultivates (about1.0～961.9multiply high), it suggested that stronger cold-resistance of wheat was largelydependent on higher expressions of COR genes, and the significant different expression ofWcor719between frost-tolerant and frost-sensitive cultivates indicate that Wcor719is a keyCOR gene of wheat for spring frost tolerance. In addition, highly tissue specificity of theexpression of three COR genes are obviously present which were deferent expressed betweenleaf and stem in four cultivates. On the other hand, statistical analysis showed that there was asignificant decline for the grain yield per plant (GYP) of wheat after low-temperaturetreatment, Shan229and Xinong979(decrease46.01%and38.13%separately) show a betterresistance and the GYP deceased relatively less than Shaimai139and Zhengmai9023(decrease73.61%and78.69%separately). The correlative analysis showed that theexpression of WCS120, WCS19and Wcor719was negatively correlated with the drop ofwheat production (r=-0.677~0.993**), especially for Wcor719, the correlation coefficientbetween expression and yield decrease was highly significant (P≦0.05). This was moreconfirmed the importance of Wcor719for spring frost in our research.