Control Effect Of Combined Application Of Compound Bacteria And Different Ratios Of Nitrogen, Phosphorus And Potassium On Banana Fusarium Wilt Disease

Banana Fusarium wilt disease is one of the soil-borne fungal diseases that seriously affect the development of banana industry.At present,the comprehensive prevention and control of banana wilt by using antagonistic microorganisms is more effective.The effective nutrients and their ratios in rhizosphere soil of plants can directly affect the species and quantities of rhizosphere microorganisms and antagonistic activities,and then affect the resistance of plants to the pathogens.At the same time,as one of the necessary elements for plant growth,phosphorus exists in insoluble forms in soil,which is difficult to be absorbed and utilized by plants.Therefore,screening microorganisms with high phosphorus-solubilizing ability is a good way to solve the problem of phosphorus utilization in plants,and it also lays the foundation for the production of multifunctional compound microbial fertilizer with phosphorus-solubilizing microorganisms and antagonistic microorganisms.In this study,the screening of phosphate-solubilizing bacteria in soil and the compatibility between phosphate-solubilizing bacteria and two biocontrol antagonistic Bacillus strains,the effect of concentration and ratio of nitrogen,phosphorus and potassium active ingredients on the biological activity of compound bacteria,and the effect of combined application of compound bacteria and fertilizer on the soil physical and chemical properties,and plant growth,and incidence of banana wilt were studied.The experimental results were as follows :(1)A strain of bacteria with high phosphorus-solubilizing efficiency was screened from watermelon rhizosphere soil.By observing the morphological characteristics,analyzing the physiological and biochemical characteristics and comparing the 16 S r DNA gene sequence,it was identified as Bacillus subtilis and named as GS032.The strain had the highest phosphorus-solubilizing efficiency on the third day.The available phosphorus content increased significantly with the increase of initial inoculation amount,and the phosphorus-solubilizing efficiency was better under the initial p H acid condition.(2)After phosphate-solubilizing bacteria GS032 and their combination with biocontrol bacteria X5 or QB61 were co-cultured,the content of available phosphorus in the fermentation supernatant was not significantly different.It shows that there is compatibility between X5 or QB61 and Bacillus subtilis(GS032).By changing the concentration and proportion of N,P and K in the medium,the antagonistic efficiency of the supernatant of the fermentation medium after the compound culture of phosphate-solubilizing bacteria and antagonistic bacteria against Fusarium oxysporum f.sp.cubense was determined.It was found that when the total concentration of N,P and K was 30 mg/L,the antagonistic effect of the strong antagonistic strain X5 or the weak antagonistic strain QB61 was all increasded obviously.The antagonistic circle of the fermentation medium of X5+GS032 compound bacteria against Fusarium oxysporum was 2.31 cm,and that of QB61+GS032 against Fusarium oxysporum was1.83 cm.When the ratio of N,P and K was 3: 2:4,the antagonistic effect of the compound bacteria was obvious.The antagonistic circle of X5+GS032 compound bacteria against Fusarium oxysporum was 2 cm,and that of QB61+GS032 compound bacteria was 1.93 cm.X5+GS032 fermentation supernatant also inhibited spore germination and colony growth of Fusarium oxysporum.(3)Under the combined application of composite bacteria with different ratios of N,P and K,the contents of soil alkali-hydrolyzable N,available P,available K,plant chlorophyll,and stem girth reached good results under the combined N1 C,N2C,K1 B,N1C and N2 C treatments,which were 59.17 mg / kg,188.17 mg / kg,256.2 mg / kg,42.1SPAD,and 15.44 cm,respectively.Compared with the control CKA(only clean water),it was 99%,147%,56.1%,77.3%,63.5% higher,respectively.Among 15 kinds of bacteria and fertilizer combined treatments,K2 C treatment had the most obvious control effect.Under K2 C treatment,the incidence of banana wilt was 42.9 %,the disease index was 10.7,and the control effect was 72.7 %.In this study,15 kinds of compound bacteria combined with nitrogen,phosphorus and potassium fertilizer were used to screen the combination of compound bacteria and nitrogen,phosphorus and potassium,which was beneficial to plant growth and reduce the incidence of banana wilt,and provided a new functional strain and theoretical reference for the development of multifunctional and highly effective microbial fertilizer.