Effects of jointing and booting low temperature stresses on grain yield and yield components in wheat

Climate change has brought more low temperature events and posed an increasing risk to the global wheat production. In order to evaluate the effects of low temperature at jointing and booting stages on wheat grain yield and its components, two years of environment-controlled phytotron experiments were carried out with two wheat cultivars under different low temperature levels and durations. Low temperature level and its interaction with low temperature duration had negative effects on the observed grain yield in two cultivars. Moreover, wheat yield was more sensitive to low temperature at booting than at jointing stages. Compared with the control treatment (T-min/T-max/T-mean of 6 degrees C/16 degrees C/11 degrees C, T1), 4.6%-56.4% and 3.1%-44.6% decreases of grain yield per plant (YPP) were observed under low temperature at jointing in Yangmai16 (spring wheat) and Xumai30 (semi-winter wheat), and 13.9%-85.2% and 3.2%-85.9% decreases under low temperature at booting in Yangmai16 and Xumai30, respectively. The spike number per plant (SNPP) and grain number per spike (GNPS) were more sensitive to low temperature at jointing and booting stages than 1000-grain weight (TGW). Furthermore, significant negative linear relationships were observed between the accumulated cold degree days (ACDD) and YPP, SNPP, GNPS and TGW in both cultivars. The contribution of GNPS to the variation of YPP was greater than SNPP and TGW at the mild low temperature level (T-min/T-max/T-mean of - 2 degrees C/8 degrees C/3 degrees C, T3) in both cultivars. However, at the extreme low temperature level (T-min/T-max/T-mean of - 6 degrees C/4 degrees C/ -1 degrees C, T5), the major variation of YPP was caused by SNPP of Yangmai16 and GNPS of Xumai30. In general, the decreased YPP under low temperature condition was mainly from the decreased grain number per plant (GNPP = SNPP x GNPS) in both cultivars and treatment stages, thus maintaining a high GNPP is very important for compensating the yield losses caused by low temperature at jointing and booting stages.