Effects Of Soil Main Organic Phosphorus On Growth,Toxicity And Pathogenicity Of Fusarium Graminearum

Fusarium graminearum is the main pathogen causing common soil-borne diseases such as corn stalk rot,which has a serious impact on corn yield and quality.In recent years,with the change of climate environment,farming methods and fertilization system,the incidence of corn stalk rot in China has been on the rise,especially the change of fertilization system.The large amount of fertilizer application has continuously increased the cultivated land fertility,but also caused the condition of stem rot is getting worse year by year.In order to clarify the relationship between soil organic phosphorus and disease occurrence in cultivated land fertility factors,the rapid detection technology of mycotoxins and potted plants and field inoculation tests were used.The study found that with the increase of organic phosphorus content,the growth of Fusarium graminearum,Toxicity and pathogenicity have been significantly improved,which aggravates soil borne diseases such as corn stalk rot.In this study,Fusarium graminearum provided by the Microbiology Laboratory of Jilin Agricultural University.Lecithin,phytic acid and K₂HPO₄ were set as the only phosphorus source in Czapek medium,and the specific design principles were as follows:The addition amounts of K₂HPO₄ per 100 ml medium were set to 1 mg,10 mg,100 mg and 1000 mg,respectively.Then,K₂HPO₄ in the medium was replaced by lecithin and phytic acid in equal amount of substance.The calculated adding amounts of lecithin were 4.5 mg,45 mg,450 mg and 4500 mg respectively,and the adding amounts of phytic acid were 0.75 mg,7.5 mg,75 mg and 750 mg respectively.After the cultivation,compare the differences of different phosphorus sources on the growth,toxicity and pathogenicity of Fusarium graminearum,and make a preliminary analysis of the test results.The main research results of this paper are as follows:1. Using lecithin,phytic acid and K₂HPO₄ as the sole phosphorus sources,Fusarium graminearum was cultured in the solid medium of Czapek,and the change of the diameter of Fusarium graminearum colony was measured by cross method every day.The results showed that compared with the control group,the three phosphorus sources could promote the growth of Fusarium graminearum.Among them,the lecithin group had the fastest colony growth rate.When the amount of lecithin added per 100 ml medium was 450 mg,the colony diameter reached 8.5 cm on the 6th day of culture.Phytic acid and K₂HPO₄ had no significant difference in promoting colony growth,but they were not as good as lecithin.The dry weight of mycelium in the culture medium with lecithin was significantly higher than that of the other two groups?P<0.05?.The highest dry weight of mycelium was 0.28 g·L^-1.Both test results show that lecithin can significantly promote the growth of Fusarium graminearum.2. The results of the bioassay of corn seeds and the determination of DON toxin in the fermentation medium showed that the fermentation medium supplemented with lecithin and phytic acid had a significant inhibitory effect on the germination of corn seeds and the growth of radicle and germ,when the amount of lecithin added per 100 ml of medium is 4500 mg,the inhibition rate of the fermentation broth on the germination of corn seeds can reach 56.7%,and the inhibition rates on the radicle and germ can be as high as 95.03%and 89.49%.The inhibition rate of seed germination was only 16.7%,and the inhibition rates of radicle and embryo were 75.76%and 70.56%.The inhibitory effect of phytic acid and lecithin were significantly stronger than K₂HPO₄?P<0.05?.The inhibitory effect on corn seed growth became more obvious with the increase of the amount of phosphorus source added.Moreover,the results of the DON toxin test in the fermentation broth proved that the toxin content also increased with the addition of lecithin and phytic acid.When the amount of phytic acid added per 100 ml medium is 0.75 mg,the toxin content in the fermentation broth was only 69.87?g·L^-1,and when the added amount is 750 mg,the toxin content can reach 580.79?g·L^-1.The results of DON toxin determination in the fermentation broth showed that the main organophosphorus of the two soils could significantly promote Fusarium graminearum to produce more DON toxin compared with K₂HPO₄?P<0.05?.3. Inoculated Fusarium graminearum under different phosphorus source culture conditions at the seedling stage and the silking stage of corn,investigated the statistical occurrence of diseases,and compared the pathogenicity according to the disease-level evaluation criteria and disease index.The results showed that Fusarium graminearum were more pathogenic than K₂HPO₄ under the culture conditions with lecithin and phytic acid?P<0.05?.When the amount of lecithin added per 100 ml of medium was 4500 mg,the incidence rate of corn seedling roots was 100%,the disease index was 95,the incidence rate of corn seedlings stems was 98.33%,and the disease index was 94.55;When the amount of phytic acid added per 100 ml of medium was 750 mg,the incidence of roots at the seedling stage of phytic acid was 100%,and the disease index was 85.The incidence of phytic acid stems was 90%,and the disease index was89.60.When the amount of K₂HPO₄ added per 100 ml of medium was 1000 mg,the incidence rate of K₂HPO₄ seedling roots was 86.67%,the disease index was 56.67,the stem incidence rate was 76.66%,and the disease index was 72.41.The results of the corn spinning stage and the seedling stage were consistent,which proved that lecithin and phytic acid,the two main organic phosphorus in the soil,could significantly increase the pathogenicity of Fusarium graminearum compared with K₂HPO₄.