Screening Of Antagonistic Bacteria Against Lily Fusarium Wilt And Exploration Into Its Possibility For Biological Organic Fertilizer

Lily is an ornamental plant with medicinal and edible properties.Due to its high economic value,lily plant is widely cultivated throughout the country.However,lily cultivation is significantly hindered by soil-borne fungal diseases such as lily blight caused by Fusarium oxysporum.This disease is of great concern to farmers as it causes significant yield loss.Several control methods have proven successful against Lily Fusarium Wilt.Chemical control method via the use of pesticide has been widely adopted due to its simple operation,easy promotion and effectiveness.However,long-term use of chemical agents result in environmental pollution,increased immunity of pathogens to chemical agents,and decline in yield and quality of lily..To overcome the problems associated with chemical control method,a better alternative,biological control method,has been widely adopted.The biological preventive and control method is a safer,more effective and sustainable method of disease control.Thus,it is of great significance to ecological balance and agricultural development..In this study,Fusarium oxysporum P-OF,the main pathogen of Lily Fusarium Wilt in Yixing,was used as material.The pathogenic concentration of lily fusarium wilt pathogen and its effect on the growth of lily was explored in a pot experiment.Through the plate confrontation experiment,strains with antagonistic effect on the pathogen P-OF were selected from the rhizosphere soil of different plants in Guizhou Botanical Garden and healthy plants in the diseased plots of Yixing Lily in Jiangsu.The antagonistic strains and the decomposed amino acid straw compost were subjected to secondary fermentation to prepare special bio-organic fertilizer for lily.Through field experiments,the biological effects of lily was explored for the possibility of special biological organic fertilizer.The results obtained are as follows:1.The pot experiment showed that when the spore concentration of pathogenic bacteria in the soil reached 10² cfu·g^-1,the plant disease rate was 0,the disease index was10%,and there was a potential disease phenomenon.When the spore concentration of the pathogen was 10³cfu·g^-1～10⁵cfu·g^-1,the plant was obviously infected,and the degree of the disease increased with the increase of the spore concentration.When the spores concentration was greater than or equal to 10⁵cfu·g^-1,the incidence rate was 100%,the disease index was 100%,and the plant was completely withered.2.Eight strains with obvious antagonistic effect were isolated from rhizosphere soil using P-OF as target bacteria,among which BH-1 had the strongest antagonistic effect.The bacterium was identified as Bacillus velezensis.Through the optimization of culture conditions,the optimal p H range of BH-1 culture was 5～9,the preferred carbon source was glucose,and the preferred nitrogen source was peptone.The antagonistic strains BH-1and HQWBH2（provided by the Farmland Soil Microbial Ecology Laboratory,College of Resources and Environmental Sciences,Nanjing Agricultural University）were separately fermented with the decomposed amino acid straw to prepare a special bio-organic fertilizer for lily.During the six-month shelf life,the effective viable counts of the two fertilizers were both greater than 2×10⁸ cfu·g^-1.3.The results of the field experiment showed that compared with chemical fertilizer application alone,T11 and T22 could significantly promote lily growth and increase lily yield by 13.8%and 13.5%,respectively,and thus,improved its nutritional quality.The contents of total sugar,soluble sugar,polysaccharide and polyphenol in the bulbs of lily treated with T11 were 1.5 times,1.8 times,1.5 times and 1.3 times than that of single application of chemical fertilizer,respectively;while the T22 treatment was 1.4 times,1.4times,1.1 times and 1.4 times,respectively.Compared with the application of chemical fertilizers,the number of bacteria and actinomycetes in the soil increased significantly,and the number of fungi and Fusarium oxysporum decreased significantly in the T11 and T22treatments,and the soil microbial community structure was optimized.Compared with the application of chemical fertilizers,the contents of total phosphorus,total nitrogen and available nutrients in the soil were significantly increased in T11 and T22 treatments,and in turn stabilized the soil p H and improved the physical and chemical properties of the soil.In In summary,the application of lily special biological organic fertilizer can improve the physical and chemical properties of soil,optimize the structure of soil microbial community,reduce the number of Fusarium oxysporum and fungi in soil,greatly reduce the probability of Lily Fusarium wilt,so as to promote the growth,and improve the yield and quality of lily.