Comparisons Of Phosphine Resistance Of Five Cryptolestes Ferrugineus Populations From Hubei And Primary Studies Of Their Oxidases

Cryptolestes ferrugineus(Stephens) is one of the major stored grain pests which waswidely distributed around in tropical and subtropical region. Both larvae and adults cancause serious damages to the incomplete raw grains, which causes serious losses to storedgrains. Currently, phosphine fumigation is the main method for controlling stored-productinsects in many countries. However, repeated ineffective fumigation in poorly sealedstructures resulting in under-dosing has led to the development of strong resistance intarget pest. In this study, we report:(1) phosphine resistacne of five populations of C.ferrugineus from Hubei province, which were collected from Xiangyang、Zhongxiang、Wuhan、Jinzhou and Macheng and named as XYCF, ZXCF, WHCF, JZCF and MCCF,respectively;(2) Comparisons the activities of catalase (CAT), superoxide dismutase (SOD)and peroxidase (POD) in five different resistance populations of C. ferrugineus;(3)Cloning catalase gene fragment of Sitophilus zeamais(Motschulsky).1. Phosphine resistance of C. ferrugineus from different regions in Hubei provincePhosphine was produced by Zinc phosphide and concentrated sulphuric acid reaction,and collected by drainage method. The homemade phosphine gas concentration was0.853mg/ml detected by the method of molybdenum blue colorimetric, which could meetthe requirements of the follow-up study. Phosphine resistance in five populations of C.ferrugineus collected from different regions of Hubei province were detected through themethod recommended by FAO．The result showed that the phosphine resistance factors ofXYCF, ZXCF, WHCF, JZCF and MCCF were4.4,7.4,8.3,197.5and838.4, respectively,compared with susceptible population. According to the phosphine resistance index, thefive populations were susceptible, low resistance, low resistance, sky-high resistance andsky-high resistance populations, respectively. The result also showed that phosphineresistance level among five populations of C. ferrugineus was significantly different.2. Effects of phosphine fumigation on three protective enzymes of C. ferrugineus adultsin different populationsWe detected the activities of catalase (CAT), superoxide dismutase (SOD) andperoxidase (POD) in the five C. ferrugineus populations. The results showed that therewere significant correlatio between the activities of CAT, SOD, POD and the LC50beforefumigation (P<0.05), while the CAT activity showed no significant correlation with the POD activity (P>0.05). There were different capacity in decomposing hydrogen peroxideamong five different geographical populations of C. ferrugineus because of different Kmand Vmax of CAT.The activities of CAT in five different populations of C. ferrugineus adults decreasedafter phosphine fumigation treatment, while the activities of SOD and POD enhanced. Butit cloud not immediate showed that the C. ferrugineus adults were dead with the CATdecreasing after phosphine fumigation, because hydrogen peroxide cloud be decomposedalso by GST. There were significantly different in the I50of CAT between low and highphosphine resistance populations of C. ferrugineus. But it also cloud not showed that theCAT of low resistance populations were more susceptible than the high resistancepopulations of C. ferrugineus for phosphine abundantly, because the resistance populationsof C. ferrugineus might reduce the rate of respiration around phosphine.3. Cloning of the catalase gene fragment in Sitophilus zeamais(Motschulsky)A715bp gene fragment in Sitophilus zeamais was coloned with one pair of degenerateprimer, which assumed encoding253amino acids. The gene fragment belonged to thecatalase family by identity analysis in NCBI. The identity reached82%between S. zeamaisand Tribolium castaneum(Herbst), another stored grain pest. But the catalase genefragment of C. ferrugineus was not got with the same primers.