Identification And Mechenisms Of Corn Resistence To Tetranychus Urticae Koch In Ningxia

The research was established on 5 varieties in Ningxia, Xianyu335, Zhengdan 958, Zhengdal2, Ximeng6, Pingyu 8. Tetranychus urticae as research object. On the basis of field experiment, discharge from the basis of field experiment, physical and chemical defense effect, secondary metabolites and the effect of enzymology to mite was studied.Through the above research explored the mechanism of mite-resistant and achievable evaluation indicator.These provides the technology, theory and material foundation design innovation and utilization of corn breeding for resistance to mite molecules. The results are in below:1 The Ningxia Tetranychus urticae population combined with 15 populations that quote from Genbank was investigated by the sequence in the mtDNA gene coding for cytochrome oxidase I (COI). DNA analysis about COI sequence showed that the A+T contents was more dominant than G+C. Besides Taiwan, Jiangxi and Guangdong population, the remaining seven domestic populations had fewer genetic variation points (<5). Especially the Kunming and Xian population only had 1 variation points. There are significant differences among foreign geographical populations. Spain castello genetic variation was lower than remaining 5populations which can called high variation. All the research above showed that the features of Tetranychus urticae population in Ningxia.2 The population dynamics of Tetranychus urticae in Ningxia.A survey was carried out to understand the occurrence of Tetranychus urticae from May to September. The results showed that as follows:the natural population dynamics of Tetranychus urticae was fluctuant increasing process. The population on Pingyu8 was higher aggregation in slowly increased period. Ximeng 6 was bigger than others in quickly increased period. Based on the index of DMI and DMR, Xianyu335, Zhengdan 958 and Zhengdal2 were strong resistant variaties.3 The life-table parameters of Tetranychus urticae were compared on five different maize cultvars, Zhengdan 958, Xianyu 335, Zhengda 12, Pingyu 8, Ximeng 6. It not only can explore the mechanism of antibiosis but also provide theoretical basis for future maize breeding. The experiments were conducted at T=25±1℃, L:D=16:8h, and RH=20%, using leaf discs to breed maize in Petri dishes. The results showed that there were some significant differences in the post-nymph duration, preoviposition duration, oviposition duration, fecundity, net reproductive rate(R0), finite rate of increase (λ), intrinsic rate of increase(rm), mean generation time (T), and the days needed to double population size(t) of T. urticae, on five different cultivals. There were also some differences in the survival curves. Ximeng 6 was belongs to deevey I, Pingyu 8 was belongs to deevey Ⅱ.others are between deevey I and deevey Ⅲ. T. urticae had the highest net reproductive rate on Pingyu 8(13.14), and the lowest on Xianyu 335(5.98). In conclusion, the mites prefer Pingyu 8 and Ximeng 6 to Xianyu 335 and Zhengdan 958.4 The physical defense effect to Tetranychus urticae was studied. The result showed there were some correlation between the Chlorophy content, stomatal conductance(GS), transpiration rate(E) and corn resistance. This method could be used as an resistance evaluation index in the future. The wax content as resistance evaluation standard, the order was Zhengdan958>Xianyu335>Ximeng6> Zhengda12>Pingyu8. Zhengdal2’s stomatal conductance (GS) and photosynthetical system was the highest than others.In total, the photosynthetic system parameters in Zhengdal2 and Xianyu335 were stronger than other varieties. Based chlorophyll content on different varieties and insect levels the chlorophyll A and B and total chlorophyll content in Zhengdan958 and Xianyu335 were higher than others.5 The chemical defense effect to Tetranychus urticae was studied. The results showed the content of tannin and phenol was used as resistence evaluation, Xianyu335 was the strongest, Ximeng6 took the second place. The nutrition of free amino acids Ximeng6>Xianyu335>Zhengda12>Zhengdan958> Pingyu8. The activity of protective enzymes of PPO SOD CAT the order was Xianyu335>Zhengdal2 >Ximeng6>Pingyu8>Zhengdan958. Xianyu335 and Ximeng 6’s activity of etoxification enzymes of Ache and GST were stronger than others. Based on chemical defense effect to Tetranychus urticae was Zhengdan958 and Xianyu335 were stronger than other varieties.