The Effect Of High Temperature On The Development And HSPs Expression Of 3 Different Strains Of Tetranychus Cinnabarinus

Tetranychus cinnabarinus(Boisduval)belongs to Arachnida,Acarina:Tetranychidae.This mite, a very important agricultural pest,is polyphagous and can harm many different kinds of corps, which makes the problem of its resistance of pesticide critical on agriculture.This paper selected 3 different strains of Tetranychus cinnabarinus,which were susceptive strain,S,anti-Avermectin strain,RA and heat-tolerant strain,RH by long term rearing.And the development and fecundity were investigated as well as the life tables were built at 40℃±1℃on the 3 strains.Furthermore, the effect of heal shock on resistance of Avermectin was studied on the 3 different strains as well as the relationship between heat shock protein,HSPs and resistance of pesticide and heat.The results are as follows:1 The selection and rearing of the 3 different strains of Tetranychus cinnabarinusThe mite collected on the cowpea field from Beibei,Chongqing were transferred onto new fresh cowpea plantlets in the lab.The mites which were free of any pesticide for 7 years,i.e.about 110 generations were defined as susceptive strain,S.A sub-population separated from susceptive strain were sprayed with Avermectin for 48 generations developing a strain which resisted Avermectin 10.57-fold high than the susceptive strain was defined as anti-Avermectin strain,RA. Another sub-population was selected under a gradually heightened temperature at eventually reared at 38℃,named heat-tolerant strain,RH.The foundation of the 3 strains consisted the base of the following experiment.2 The effect of high temperature on the development of the 3 strains of T.cinnabarinusThe RH's larva duration was significantly longer than the S's,1.54±0.07＞1.29±0.06, respectively at 40℃±1℃.The RA's larva duration was not significantly different from the S's, though still longer than S's.And the RA's adult duration was significantly longer than the S's. Neither significant difference between RA's and RH's adult duration nor between RH's and S's was found.The RA's and RH's whole generations were longer than the S's.The 3 strains were not significantly different in egg and nymph duration,yet the S's both durations were shorter than the two.The RH strain laid significantly more eggs the other two strains and no such difference was found between the S and RA strains.3 The life table of the 3 different strains of T.cinnabarinus at 40℃±1℃The survival rate curve(Lx curve) of the 3 strains descended as the time went on at 40℃±1℃, which conveyed that the survival rate declined gradually.The shape of S's Lx curve was sharper than the other two strains which meant that the survival rate dropped fast.The RA's and RH's Lx curve showed relatively smoother than the S's and the trend of the two was almost the same which reflected they were more adaptive to high temperature than the S's.The innate capacity for increase, r_m of the RH',i.e.r_mRH was the biggest equaling 0.2976.The r_mRA and r_mS were 0.1791 and 0.1765, respectively.No significant difference was found between the S's and RA's R₀,the net production rate and the RH's R₀ was the biggest equaling 9.8162.The finite rate of increase,λof RH was the biggest equaling 1.3466,the other two's were 1.1930 and 1.1961,respectively,which indicated that the population of RH strain increased faster than the S and RA.The population double time of RH, T_bRH was the smallest equaling 2.3291d,and the T_bRA and T_bS were 3.3829 and 3.9272d,respectively.4 The effect of heat shock on the resistance of Avermectin of the 3 strains of T.cinnabarinusBefore the heat shock,the LC₅₀s of S,RA and RH were 0.0137±0.0007,0.1417±0.0139 and 0.0576±0.0054 mg/L,respectively,which indicated that the order of the resistance level was RA^h-＞Rh^h-＞S^h-.The slopes of the LC-P lines of S,RA and RH were 3.5045,2.9525 and 3.3692, respectively,which indicated that the population variation in RA and RH was relatively smaller than S did,i.e.S was more susceptive of Avermectin than the former two strains.After the heat shock,the LC₅₀s of S,RA and RH were 0.0176±0.0014,0.1436±0.0159,0.0593±0.0047mg/L,respectively,which reflected the resistance ranked as RA^h+＞RH^h+＞S^h+.The slopes of the LC-P lines of S,RA and RH were 3.4558,2.8327 and 3.1948,respectively,with the same trend before the heat shock..5 The effect of heat shock on the expression of HSPs of the 3 strains of T.cinnabarinus The SDS-PAGE map showed that before the heat shock,RA^h- expressed 7 more bands than S^h-, which belongs to HSP90,HSP70,HSP60 and sHSP families,whereas RH^h- expressed 5 more bands than S^h-,4 located in 50～100kDa which showed that the specific bands distributed mainly in the HSP90 and HSPT0 families.After the heat shock,4 more bands were expressed in S strain with the molecular weight of 75,62.7,53.3 and 30.3kDa which was accord with RA^h-.The color of the specific bands of RA^h+ deepened after the heat shock,especially those locate in the HSP90 and HSP70 families,which indicated the content increased.The accordance suggested that it was these specific HSPs that played an important role in the heat stress response.The bands of RH^h+ did not increase or decrease and merely the content changed a little after the heat shock.