| Tagetes erecta L belongs to the genus Tagetes,Pelargonium hortorum belongs to the genus Pelargonium,Begonia semperflorens belongs to the genus Begonia,and Hosta undulata belongs to the genus Zea.All four plants have higher food,medicinal,ornamental and ecological values.The author’s investigation found that Tagetes erecta L,Pelargonium hortorum,Begonia semperflorens,and Hosta undulata were all susceptible to leaf spot disease.In severe cases,the whole plant will die.Therefore,it is critical to identify the cause of the leaf spot disease.In this paper,the leaf spot diseases of Tagetes erecta L,Pelargonium hortorum,Begonia semperflorens,and Hosta undulata,were identified and identified,and their biological characteristics were studied.The endogenous antagonistic effects of four plants,Tagetes erecta L,Pelargonium hortorum,Begonia semperflorens,and Hosta undulata,were screened out.Bacteria,and the inhibitory effect of antagonistic bacteria and pesticides on pathogenic bacteria were tested.The experimental results are as follows:1.The identification of pathogen of leaf spot on Tagetes erecta L,Pelargonium hortorum,Begonia semperflorens,and Hosta undulata:Eight pathogenic fungi are Alternaria citrimacularis,Nigrospora sphaerica and Alternaria compacta,Acremonium strictum and Alternaria alternata,Alternaria chlamydosporora and Alternaria solani,Alternaria tenuissima.2.The biological characteristics of Eight pathogens of Tagetes erecta L,Pelargonium hortorum,Begonia semperflorens,and Hosta undulata:(1)The mycelia of the 8 kinds of pathogenic bacteria stopped growing at 5°C and did not produce spores.The hyphae could grow and produce spores in the temperature range of10-35°C.The optimum temperature for the eight species of bacteria was 25°C.The diameter of the colonies and sporulation were the highest at this temperature.(2)The eight pathogenic bacteria can grow at a pH of 4-10,but G2 and D2 do not produce spores at a pH of 4.When pH value is 6,with the exception of D3 and E2,the other 6species have the largest colony diameter and fast growth rate.The D3 and E2 have the largest colony diameter and the fastest growth rate at pH=9.It can be seen that in addition to D3 and E2,the other 6 species of bacteria are suitable for growth in a partially acidic environment,while D3 and E2 are suitable for growth in a more alkaline environment.(3)The 8 kinds of pathogenic bacteria can grow in the relative humidity of 30%-90%,but D3 does not produce spores under the humidity less than 50%.Humidity has little or nosignificant effect on colony growth.(4)Among the 8 pathogens except G2,C1 and E2,there was no significant difference in the effect of light on the colonization of other 5 pathogens,but the effect on sporulation was significant,and the significant difference was obvious on C1.Under full dark conditions,sporulation of C1 is approximately 20 times greater than that of sporulation under alternating light and dark conditions.Except for D3,all other 7 pathogenic bacteria produced spores under the conditions of full darkness,indicating that the full dark condition was more conducive to the spore production of the 7 pathogens,and the optimal sporulation environ-ment of D3 was full illumination.(5)Effect of Nutrients on Mycelia Growth and Sporulation of Pathogenic Fungi:Carbon sources,nitrogen sources,inorganic salts,and growth factors have different effects on mycelial growth and sporulation of eight pathogenic bacteria.3.The antibacterial effects of antagonistic bacterium and pesticides on pathogens of leaf spot: After identifying,the author found that the endophytic antagonistic bacterium,Paecilomyces javonicus,Penicillium variabile,Aspergillus terreus,Paecilomyces lilacinus.These four antagonists were respectively against Alternaria citrimacularis,Alternaria chlamydosporora,Alternaria solani and Alternaria tenuissima.The four pesticides,difenoconazole,mancozeb,carbendazim,and thiophanate-methyl,all had different degrees of bacteriostatic effect against the eight pathogens,but the inhibitory effect of difenoconazole was significantly better than The antibacterial effect of the other three pesticides,the antibacterial rate of difenoconazole of 200 μg/ml to 8 kinds of pathogenic bacteria reached more than 70%. |
