| Dolycoris baccorum(L.)is a polyphagous pest,which harms a variety of crops,vegetables,forest trees,fruit trees,forages and ornamental plants.Adults or nymphs suck the sap of young leaves and stems of plants,especially at heading and filling stages.Small yellow-brown spots will appear in the injured leaves,which will lead to leaf drying,affect the normal development of plants and reduce production.Dolycoris baccorum are widely distributed in Inner Mongolia.In order to understand the cold tolerance of Dolycoris baccorum at low temperature,the supercooling point,free water content,total sugar content,trehalose content and glycogen content of male and female adults were determined after gradient cooling domestication and direct cooling domestication.The results are as follows:1.Effects of gradient cooling domestication and direct cooling domestication on the supercooling point of Dolycoris baccorumThe supercooling points of Dolycoris baccorum adults after gradient cooling domestication and direct cooling acclimation were determined.Gradient cooling domestication(diapause adults obtained at 25℃ in short days were placed at 15 ℃,10 ℃,5 ℃ and 2 ℃ for gradient cooling acclimation,15℃ for 2 days,then moved to 10℃ for 2 days,then moved to 5℃ for 2 days,and finally moved to 2℃ for 2 days),the supercooling points of male and female adults are-15.54 ± 0.47℃(♀)and-16.21 ±0.35℃(♂),respectively.Direct cooling domestication of diapause adults at 15℃: 8d,10℃: 8d,5℃: 8d,2℃: 8d,respectively.The supercooling points of domestication are-12.25 ± 1.98℃(♀)and-12.97 ± 0.72℃(♂)at 15℃,-13.00 ± 0.88℃(♀)and-13.97 ± 1.05℃(♂)at 10℃,-13.76± 1.83℃(♀)and-14.33 ± 0.81℃(♂)at 5℃,-14.09 ± 0.54℃(♀)and-15.35 ± 0.51℃(♂)at 2℃,respectively.The supercooling points of the undomesticated control group(25℃: 8d)were-11.72 ± 0.94℃(♀)and-12.46 ± 0.66℃(♂),respectively.Both gradient cooling domestication and direct cooling acclimation could decrease the supercooling point of both male and female adults,and the supercooling point of gradient cooling acclimation decreased significantly(P < 0.05).2.Effect of gradient cooling domestication and direct cooling domestication on free water content of Dolycoris baccorumThe free water content of Dolycoris baccorum adults domesticated by gradient cooling and direct cooling was determined.The results showed that the free water content of male and female adults after gradient cooling and domestication was 45.04 ± 3.85%(♀)and 40.20 ± 3.60%(♂),respectively.After direct cooling and domestication,the free water contents of male and female adults were 62.80 ± 4.37 %(♀)and 55.34± 4.31%(♂)at 15℃、60.45 ± 4.68 %(♀)and 55.05 ± 3.02%(♂)at10℃、59.01 ± 4.71 %(♀)and 52.21 ± 2.25%(♂)at 5℃、51.83 ± 4.35 %(♀)and 49.27 ± 1.51%(♂)at 2℃,respectively.The free water content of the control group was 63.84 ± 1.55%(♀)and 61.09 ± 1.99%(♂),respectively.The results showed that the free water content decreased significantly after gradient cooling domestication(P < 0.05),which was positively correlated with the domestication temperature.3.Effects of gradient cooling domestication and direct cooling domestication on the total sugar content of Dolycoris baccorumThe experiment measured the total sugar content of the Dolycoris baccorum after after different domestication methods.The total sugar content of male and female adults in the control group was 97.64 ±2.06μg/g(♀)and 91.13 ± 1.63μg/g(♂).The total sugar content of the female and male adults of the Dolycoris baccorum after gradient cooling and domestication is 117.41 ± 3.78μg/g(♀)and 105.06 ± 4.57μg/g(♂).The total sugar content of the female and male adults of the Dolycoris baccorum after direct cooling and domestication was 120.72 ±7.77μg/g(♀)and 116.73 ± 0.98μg/g(♂)at 15℃、122.98 ± 6.17μg/g(♀)and 148.28 ± 1.18μg/g(♂)at 10℃、115.99 ± 4.48μg/g(♀)and102.03 ± 1.07μg/g(♂)at 5℃、111.41 ± 8.77μg/g(♀)and 100.70 ±2.19μg/g(♂)at 2℃.After low-temperature domestication,the total sugar content of the Dolycoris baccorum has increased to varying degrees,which is related to the improvement of cold resistance.4.The effect of gradient cooling domestication and direct cooling domestication on the trehalose content of the Dolycoris baccorumThe trehalose contents of male and female adults domesticated at different low temperatures were determined.The trehalose contents of male and female adults in the control group were 2.74 ± 0.21μg/g(♀)and 2.47 ± 0.40μg/g(♂),respectively.The values of gradient cooling domestication were 8.39 ± 0.69μg/g(♀)and 6.86 ± 0.93μg/g(♂),and the direct cooling acclimation were 4.51 ± 0.23μg/g(♀)and 4.01 ±0.37μg/g(♂)at 15℃、7.93 ± 0.33μg/g(♀)and 12.15 ± 1.22μg/g(♂)at 10℃、4.22 ± 0.82μg/g(♀)and 3.91 ± 0.37μg/g(♂)at 5℃、9.14 ±0.71μg/g(♀)and 4.06 ± 0.45μg/g(♂)at 2℃,respectively.The results showed that the trehalose content increased significantly after low temperature domestication(P < 0.05).Although the trehalose content increased greatly after direct cooling and domestication,the trehalose content changed greatly.The trehalose accumulation in the process of gradient cooling and domestication was significant.5.The effect of gradient cooling domestication and direct cooling domestication on the glycogen content of the Dolycoris baccorumThe glycogen content of gradient cooling acclimation and direct cooling acclimation was determined.After gradient cooling acclimation,the glycogen content was 24.55 ± 5.79μg/g(♀)and 27.33 ± 2.45μg/g(♂).The glycogen contents of male and female adults after direct cooling and domestication were 53.66 ± 1.06μg/g(♀)and 51.93 ± 3.37μg/g(♂)at15℃、53.68 ± 4.98μg/g(♀)and 49.69 ± 2.99μg/g(♂)at 10℃、51.18± 1.29μg/g(♀)and 46.16 ± 2.19μg/g(♂)at 5℃、53.57 ± 1.62μg/g(♀)and 47.81 ± 3.61μg/g(♂)at 2℃,respectively.The contents of glycogen in the undomesticated control group were 64.04 ± 3.63μg/g(♀)and 57.08± 1.08μg/g(♂),respectively.The glycogen content decreased with the decrease of acclimation temperature,indicating that glycogen was transformed into trehalose during low temperature,which provided the necessary energy for the body,thus improving its cold tolerance.The glycogen content of gradient cooling acclimation was significantly lower than that of direct cooling acclimation group and control group(P < 0.05),which indicated that gradient cooling acclimation was more effective in improving the cold tolerance of male and female adults. |
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