Effect Of Cold Acclimation On The Cold Hardiness And Cold Resistant Substances Of Overwintering Eggs In Ceracris Kiangsu Tsai

One of the most damaging important bamboo forest pests in southern China,Ceracris kiangsu Tsai,feeding on Poaceae such as Bamboos,it is a large feeder and difficult to control,overwintering with eggs for up to nine months.In this study,the overwintering eggs of Ceracris kiangsu were collected from Anhua,Hunan province as research material,investigated the overwintering adaptation strategy by measured the supercooling point,low temperature tolerance,the acclimation effect of rapid cold hardening and cold acclimation,and variation in cold resistant substances,which can provide a theoretical basis for understanding the population dynamics and integrated control.The main findings of the study are as follows:(1)The overwintering eggs of the Anhua population of the Ceracris kiangsu supercooling point were-23.9±4.9℃,and approximately 30%of the overwintering eggs survived after 6 h of treatment at-22℃.In combination with the winter ambient temperature of the habitat,the overwintering eggs of the Ceracris kiangsu are considered to be of the freeze avoidance.(2)Rapid cold hardening was applied to the overwintering eggs of the Ceracris kiangsu Anhua population at 0℃,4℃ and 8℃ for 6,12 and 24 h.The results showed that rapid cold hardening significantly improved the cold hardiness of overwintering eggs respectively,with the most pronounced effect at 0℃ for 12 and 24 h and at 4℃ for 12 and 24 h.(3)Cold acclimation was applied to the overwintering eggs of the Ceracris kiangsu Anhua population at 0℃,4℃ and 8℃ for 5 d,10 d and 15 d,respectively,and the results showed that cold acclimation also significantly improved the cold hardiness of the overwintering eggs,but the acclimation effect of cold acclimation gradually decreased as the acclimation time increased,with the most obvious effect of cold acclimation at 0℃,4℃ and 8℃ for5 d.(4)The glycerol,trehalose and total protein contents of the Ceracris kiangsu overwintered eggs treated with rapid cold hardening and cold acclimation were examined.The glycerol content increased significantly after rapid cold hardening,while the trehalose content did not differ significantly and the total protein content decreased;the glycerol content increased significantly after cold acclimation,while the trehalose and total protein content decreased.Both rapid cold hardening and cold acclimation induced physiological and biochemical changes in the overwintering eggs,which enhanced cold hardiness through the accumulation of glycerol.(5)A comparative analysis of the survival rate and glycerol content of overwintering eggs from rapid cold hardening and cold acclimation suggests that rapid cold hardening and cold acclimation are continuous,linked adaptation processes in response to overwintering temperature changes,and that the effect of rapid cold hardening can accumulate into the effect of cold acclimation.The present study confirms that overwintering eggs of the Ceracris kiangsu improve cold hardiness by lowering the supercooling point,and that this strategy is presumed to be of the freeze avoidance.During the long overwintering period,the overwintering eggs can be safely overwintered by coping with temperature fluctuations during the overwintering period through the acquisition of rapid cold hardening and cold acclimation effects.Rapid cold hardening and cold acclimation are continuous,linked adaptation processes in response to temperature changes during the overwintering period.