Effects of heat stress on grain-filling rate of different wheat varieties

In order to achieve high and stable yield and offer information for the selection of heat tolerant new varieties of wheat, the yield, 1000-kernel weight and grain-filling rate of 12 wheat varieties collected across the North China Wheat Belt and Huanghuai Wheat Region were studied under normal and heat treatments. The experiment was conducted in 20142015 at Malan Farm in Xinji, Hebei Province. A greenhouse was used as heating facility. Then grain-filling rate was measured for any increase in dry grain weight of different wheat varieties under normal and heated conditions. The yield and 1000-kernel weight were also analyzed after harvest. The results showed that yields of ‘Zhongmai 175’, ’Heng 4399’, ‘Heng 4444’, ‘CA0816’ and ‘Zhongmai 875’ were higher than those of other wheat varieties under both normal and heated conditions. Wheat grain weight was significantly affected by heating during rapid and slow grain-filling stages by reducing grain-filling rate. An evaluation of heat tolerance using the thermal index of yield and 1000-kernel weight showed that ‘Jingdong 8’, ‘CA0816’, ‘CA1062’, ‘Zhongmai 875’, ‘Zhongmai 895’ and ‘Heng 4444’ were heat-tolerant wheat varieties with the thermal index less than 1. Then, the other wheat varieties were heat -sensitive varieties with thermal index greater than or equal to 1. Wheat grain-filling rate, which was affected by high temperatures, differed for wheat varieties at grain-filling stage. Grain-filling rate of heat-tolerant varieties was affected at the last period of grain-filling whereas that of heat-sensitive varieties was affected at the middle period of grain-filling. In conclusion, ‘CA0816’, ‘Zhongmai 875’ and ‘Heng 4444’ wheat varieties showed both good yield and high heat-tolerance. Then ‘Heng 4399’ and ‘Zhongmai 175’ had a general thermal index for 1000-kernel weight whereas the related yield was high under both normal and heat treatments. Also ‘Jingdong 8’ showed a good heat tolerance with slightly lower yield. All the wheat varieties tested were as heat-tolerant wheat varieties for use in wheat breeding. We proposed further evaluation of both yield and thermal index of 1000-kernel weight in heat-tolerant wheat breeding.