Study On Metal Oxide Nanoparticles Improved Cotton Yield And Tolerance To Verticillium Wilt

Plant disease is one of the biotic stresses that can not be ignored in agricultural production around the world,which seriously affects crop production.Cotton is a widely cultivated economic crop in the world.Its fiber products are the main source of the textile industry,and cottonseed oil is an important edible oil source in the world.Verticillium wilt is known as the’cancer’of cotton in cotton production.About 2.5 million hectares of cotton fields are damaged by Verticillium wilt every year,resulting in more than150,000 tons of lint loss and direct economic losses of$250-$310 million,posing a huge threat to cotton cultivation and related industries.As a rapidly developing new technology,nanotechnology has great application potential in the field of agricultural science.In this thesis,we studied the effects of polyacrylic acid-modified iron-magnesium nanoparticles（FM）on the growth and disease resistance of cotton under Verticillium wilt caused by Verticillium dahliae,aiming to explore the possible mechanism of metal-based iron-magnesium nanoparticles to improve cotton Verticillium wilt resistance.At the same time,we also used FM and polyacrylic acid modified manganese oxide nanoparticles（PMO）to carry out field application for preliminary exploration of Verticillium wilt control,in order to provide more theoretical basis for the interaction between nanomaterials and crop diseases.The main results of this study are as follows:1.FM was identified as the most suitable material for improving cotton Verticillium wilt resistance compared to iron oxide nanoparticles and magnesium oxide nanoparticles.In vitro antibacterial test showed that FM had a certain effect on inhibiting the mycelial elongation and sporulation of Verticillium dahliae,and the inhibition rates were 13.6%and 21.0%,respectively.On the basis of antibacterial test,400 mg/L FM was further determined as the optimal concentration to improve the resistance of cotton to Verticillium wilt.Compared with the control,the cotton seedlings soaked in FM roots had better growth after the disease occurred,and the disease index and incidence decreased significantly（33.3%,59.2%）.2.The results showed that the development level of xylem in the vascular bundles of cotton seedlings was significantly increased by FM root soaking,and the lignin content was significantly increased by 20.6%.Verticillium dahliae infection can easily lead to the outbreak of reactive oxygen species in cotton seedlings,and excessive accumulation can easily lead to the death of normal cells.After FM treatment,the main antioxidant enzyme activities（SOD,POD）in the leaves of cotton at the theoretical onset time node were significantly increased（73.4%,13.8%）,while the content of reactive oxygen species（O₂.^-,H₂O₂）decreased（32.8%,59.9%）,which indicates that FM assists in regulating the homeostasis of reactive oxygen species in the leaves of cotton infected by Verticillium dahlia.In addition,the content of chlorophyll a and chlorophyll b in cotton seedlings with root application of FM increased significantly（10.1%,12.5%）in the subsequent growth,and the determination of chlorophyll fluorescence parameters also showed that the actual light quantum yield and the electron transfer rate of photosystem II increased significantly（21.3%,8.2%）,indicating that FM can improve the photosynthetic capacity of cotton seedlings,thereby improving their Verticillium wilt resistance3.The field application of nanomaterials in this study found that in 2021,the field yield of 20 mg/L PMO soaking group increased by 93.7 kg/hm²（9.4%）and 250.9kg/hm²（10.9%）compared with the control group,respectively.In 2022,the yield of skin and seed cotton increased by 212.8 kg/hm²（15.2%）and 496.6 kg/hm²（15.3%）compared with the control group,respectively.In 2022,the yields of 100 mg/L FM lint and seed cotton were increased by 211.4 kg/hm²（15.1%）and 432.4 kg/hm²（13.3%）respectively compared with the control.The results of field experiments showed that PMO and FM had certain application potential for increasing the yield of Verticillium wilt cotton fields.Overall,our results suggest that nanobiotechnology approach have good potential to improve cotton resistence to Verticillium wilt.Further,our results enrich the measures to control plant disease,and it also suggests that use of nanomaterials could be an effective alternative approach for plant pathogen control.