Evaluation of frost resistance of winter wheat varieties and some new countermeasures against frost damage

Developing into jointing stage and occurrence of frost temperature are two main factors for frost damage of winter wheat.The occurrence of frost temperature is mainly impacted by local climate condition,while the time of jointing stage is determined by many factors as mean air temperature in early spring,sowing time,and the varieties selected etc.Differentiation stage of young ears is an important factor that affects frost resistance of winter wheat. Therefore,evaluation of frost resistance of different varieties is suggested to be performed at a same stage in order to get reliable result.Among those stages,anther connective stage is recommended as an appropriate evaluation stage. Frost resistance of winter wheat varieties correlates with the length of the first internode,and no significant correla- tion are found between freezing resistance and content of soluble sugar of leaves.Following strategies for preventing frost damage to winter wheat are proposed:planning the planting pattern for frost resistant and frost avoiding varie- ties feasibly according to the occurrence of frost temperature in local area,improving frost resistance of the varieties through breeding and genetic engineering and enhancing frost resistance of winter wheat through genetic manipula- tion of phospholipase D.