| Callosobruchus chinensis(Linnaeus)(Coleoptera,Bruchidae),is an important worldwide of stored-been pests and had been reported in all provinces of China.Due to different regions and different generations in a year,Callosobruchus chinensis(Linnaeus)can reproduce at least 4 generations and up to 12 generations.If mungbean weevils happen and can not be controlled quickly,it will cause severe damages in the stored house.The most common and cheapest way to avoid and control Callosobruchus chinensis(Linnaeus)is chemical control,but easy to cause serious "3R" problems,and the low temperature control has a good effect.In this article,we studied the cold tolerance of Callosobruchus chinensis(Linnaeus)adults cu LTured in 28?.Mainly it was involved three aspects: the effect of low temperature on the survival of adults;determination of cold resistance index including water content,fat content,protein content,glycerol content,total sugar content;cold acclimation of mungbean weevils.We explored the cold tolerance of adults from physiological and biochemical aspects to know low temperature control better.The main resu LTs are as follows: 1.The effect of low temperature on the survival of Callosobruchus chinensis(Linnaeus)The cold resistant type of Callosobruchus chinensis(Linnaeus)was Chill susceptible,and the cold tolerance of male adults was higher than that of female adults.(1)The SCP and FP were measured by means of supercooling point measuring instrument.Results showed that: SCP and FP had gender differences,SCP and FP of male adults were lower than that of female adults.SCP and FP of male adults were-13.28 ?and-12.30?.SCP and FP of female adults were-11.72 ?and-10.65 ?.(2)The experiment was conducted to study the effect of low temperature on the survival of mungbean weevil at different low temperature conditions(-4,-2,0,2,4?).Resu LTs showed that: the survival ability of Callosobruchus chinensis(Linnaeus)was related to temperature and time,but also related to gender exposed in different constant low temperatures(-4,-2,0,2,4?).When the temperature decreased or exposure duration prolonged,the mortalities of mungbean weevil adults in the same gender increased gradually.The mortality of mungbean weevil male was lower than that of female adults under the same conditions.The half lethal time of death at-4,-2,0,2 and 4 ?were 3.88,5.67,8.86,15.08 and 19.25 d in male adults,and 2.10,4.43,7.96,11.66,15.56 d in female adults.The Lt50 s of male adults were improved about 84.76%,27.99%,11.31%,29.33% and 23.71%,copared to that of female adults.(3)When temperature changed,the internal of higher temperature can repair the damages of low tempratures and reduce mortality.When the constant low temprature was 0?,different internals of 5,15 and 28?for 2 hours significantly improved the survival,The Lt50s(5,15,28,0?)were 12.00,15.39,22.15 and 8.40 d.They were increased by 42.86%?83.21% and 163.69%,respectively.The internal of higher temperature can increase the life span,which indicated that high temperature may repair the low temperature injuries.The survivals were significantly increased at the temperature of 28?for 1,2,4 h and the life span increased.Mungbean weevil adults for 1,2,4 h and at the temperature of 0?,Lt50 s were: 17.43,22.15,18.98 and 8.40 d,increased by 107.50%,163.69% and 125.95%,respectively.Generally the internals of higher temperature may improve the survival rate,but there was a limit.2.Determination of cold tolerance indexThe mungbean weevil exposed at 0?and 2?for 5 d,the cold resistance index were measured: water content(different weight),fat content(different weight),protein content(Coomassie blue G250),glycerin(acetyl acetone method),the content of total sugar(anthrone colorimetry).Results showed that water content decreased significantly;fat content increased significantly;glycerol content changed significantly,increased first and then decreased,and most of them were lower than the control group.The changes of total sugar content also had a significant trend,reduced firstly and then increased,and most of them were lower than the control group.The protein conten significantly increased but the male adults at 2?not.All results showed that the adults under the stress of low temprature,could change their cold tolerance index to adapt to low temperature better.3.Effects of cold acclimation4 different cold acclimation treatments were carried out on the mung bean weevil: 0?for 2 h,4?for 2 h,0?for 24 h,4?for 24 h.By measuring the SCP and FP,comparing the survival rates before and after cold acclimation,comparing total egg laying amount after 36 h,cold resistance index and some enzyme activity(POD,CAT and Na~+K~+-ATP enzyme),to understand the effects of cold acclimation on cold tolerance.(1)Cold acclimation can significantly reduced SCP and FP,FP and SCP changes were not synchronized,but the trend was more consistent,SCPs were decreased by 15.41%,15.33%,11.99%,9.27%,but 4?for 24 h not significant.FPs were decreased by 12.38% 12.42%,8.15%,3.57%.FPs had been influenced less than SCP by the cold stress.(2)The effects cold acclimation had on mung bean adult survival rate: after cold acclimation,treated for 7 h at-10?,survival rate had been significantly improved.0 ?for 2 h,4 ?for 2 h,0 ?for 24 h,4 ?for 24 h survival rates were increased more by 32.22%,22.22%,30%,21.11%,respectively.(3)The male and female adults were treated for 2,24 h at 4?,and then produced eggs at 28 ?.Got egg laying amount after 36 h.The result was: the fecundity decreased significantly.Cold acclimation may cause a decline in the fertility.(4)After the cold acclimation,water content lowered,two groups of 0?for 24 h and 4?for 24 h decreased by 3.15%,5.52% significantly.The fat content increased,two groups of 0?for 2h and 4?for 24 h increased by 10.90%,8.00% significantly.Glycerol content increased,but only the group of 0?for 24 h was significant.The sugar content decreased significantly.The changes of protein content were significant.Adults may change the cold resistance index to enhance their cold resistance.(5)Cold acclimation changed the enzyme system of the Callosobruchus chinensis(Linnaeus)adults,increased the activity of protective enzymes(POD and CAT activities)and decreased the activity of metabolic enzymes(Na~+K~+-ATP enzyme activity).The activities of POD significantly increased,increased by 33.80%,42.01%,49.41%,23.57%,respectively,0?for 2h max,but the group 4 ?for 24 h not significant.The activity of CAT increased significantly,increased by 25.33%,22.35%.23.46% and 22.16% respectively.The enzyme activity of Na~+K~+-ATP was significantly decreased,and the lowest was the group of 4 ?for 24 h,which were decreased by 37.83%,70.81%,83.43% and 59.97%,respectively.In summary,freezing type of Callosobruchus chinensis(Linnaeus)adult was Chill susceptible.The mortality of male adult was lower than females in the same cold hardiness.Mungbean weevil can reduce the water content and total sugar content,increase fat content,glycerol content,and protein content and change enzyme system: to improve the activities of POD,CAT and decrease metabolic enzyme Na~+K~+-ATP activity to improve the cold resistance against low temperature environment. |
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