Effect Of Transgenic Disease-resistant Cotton On Cotton Pathogens And Biodiversity

As the major projects for national transgenic cottons carrying out, more and moregenetically modified cottons run into the stages of environmental release orpreproduction field trial.So many varieties of transgenic disease-resistant cottons comeout with the purpose to resistant to two main destructive deseases during the wholechildbearing period, fusarium wilt and verticillium wilt of cotton. Before we market thenew species, disease-resistance test is essential to make sure the gene we transformedcan be expressed successfully and achieve stable heredity, and get a better diseaseresistance effect. In addition to disease resistance, potential negative effects caused bycultivation of transgenic cotton attracted more people′s attention. So we needenvironmental safety assessment of new genetically modified cotton, for example,survival competition, the impact on biodiversity, and so on.In this study, we have a new breed of disease-resistant transgenic cotton, takezhongmiansuo75and local conventional variety lu mian yan36(yu mian21, guo shenmian958, and so on) as the control, to research the effect to soil microorganisms andthe degree of resistance to cotton′s two main pathogens: Fusarium oxysporumf.sp.vasinfectum and Verticillium dahliae Kleb. We study from five aspects: morbidityafter pathogen inoculation, changes of main physiological and biochemical indexes,antibacterial activity of tissue extract, isolation of fungal pathogens in rhizosphere soiland microbial diversity of rhizosphere soil. The experients provide reasonable plantingjudgement for transgenic cottons, meanwhile, it also has important theoretical meaningto transgenic cotton′s security management. The specific results are presented asfollows:1. Use four kinds of pathogen inoculation methods: soak in spore suspension,irrigate spore suspension, irrigate spore suspension after damage the roots, and themethod of leaf blade acupuncture, to explore disease-resistance the transgenic cotton onFusarium oxysporum f.sp.vasinfectum and Verticillium dahliae Kleb. The results showed that the leaf blade acupuncture method had an efficient effect，and thetransgenic disease-resistant cotton showed better disease-resistance than the two controlvarieties.2. After the three cotton seedling plants were inoculated with Fusarium oxysporumf.sp.vasinfectum and Verticilium dahliae Kleb, we measured the contents of solubleprotein and the activity of three major defense enzymes (POD, SOD, PAL). The resultsshowed that the soluble protein contents of transgenic disease-resistant cotton andlumianyan36showed a slight decrease trend at the beginning of the inoculation, proteindecomposition promoted formation of other plant protective substances; similarchanges in activity of several enzymes after inoculated with two kinds of pathogenicfungi, first increased and then decreased, the enzyme activity of transgenicdisease-resistant cotton changed faster, and had a higher peak, which provided areference for transgenic disease-resistant cotton varieties identification of diseaseresistance index.3. Preliminary experiments mainly for inhibition of Fusarium oxysporumvasinfectum and Verticilium dahliae Kleb with fresh tissue extraction of three cottonvarieties, a few days later, according to the inhibition zone diameter, concluded thetissue extraction of transgenic disease-resistant cotton had resistance to Fusariumoxysporum vasinfectum and Verticilium dahliae Kleb at some level.4. By collecting the rhizosphere soil of three cottons of five stages in the wholegrowth period, we have isolated9Fusarium strains using selective medium, and wefound four Fusarium oxysporum of the nine by molecular identification, none of thefour were obtained from rhizosphere soil of transgenic disease-resistant cotton. We havenot isolated Verticillium strains and Rhizoctonia strains from the rhizosphere soil. At thesame time, all varieties grew well in the experimental field, no scale diseases, onlybacterial wilt at later stage.While in another field, showed the transgenicdisease-resistant cotton varieties were tolerant to Fusarium wilt and high-resistantto Verticillium wilt.5. Surveyed the effect of transgenic disease-resistant cotton on rhizosphere soilmicroorganisms and arthropod diversity aboveground. We studied and compared the community functional diversity of rhizosphere soil microbial of five stages of threekinds of cotton during the growth period, found the rhizosphere soil microbialcommunity diversity of transgenic disease-resistant cotton is richer and showed abetter uniformity. There were significant differences between common species whichshowed that different varieties of cotton rhizosphere microbes were had differentdominant population. There were differences in various indicators in the intermediatesection of the three cottons, while in the seedling stage and harvest stage, there was nosignificant difference in terms of evenness and richness index. Meanwhile, the resultsabout arthropod diversity showed no evident influence.