Identification Of Pathogens Of Cytospora Canker Of Sorbus And Screening Of Its Antagonistic Fungi

In this paper,the author collected the specimens of Cytospora Canker of Sorbus on campus,isolation,purification,identification,inoculation test and re-isolation of the pathogenic bacteria identified the disease as Cytospora Canker of Sorbus disease and identified its pathogenic bacteria.And studied the biological characteristics of pathogenic bacteria;Based on the community composition of endophytic fungi,antagonistic strains with potential for development and utilization were screened through plate-to-limb experiments,which laid the foundation for the biological control of Cytospora Canker of Sorbus.The main findings are as follows:1.Identification of the pathogens of the Cytospora Canker of Sorbus by means of a combination of morphological and molecular biology methods.Asexuality was[Cytospora leucostoma(Speg.)Sacc.],and the sexual type was[Leucostoma persoonii(Nitschke)Hohn.],the disease is new happening to Sorbus.2.Through the experiment on the biological characteristics of pathogenic bacteria,the pathogenic bacillus--Cytospora leucostoma(Speg.)Sacc,its optimum growth temperature is 23?;the adaptability to pH is strong,ranging from 4.5 to 9.2,but the optimum pH value is 6.2;the pathogenic bacteria grow best on the medium with starch as the carbon source,and grow fastest on the medium with the peptone as the nitrogen source;Under the condition of full light,the growth of mycelium is the fastest;the conidia and conidia are more likely to be produced under semi-illumination conditions;the pathogens are prone to produce conidia and conidia under varying temperature conditions;the spore germination rate is highest at 15?;the humidity is higher,the spore germination rate is greater High,the highest germination rate is at 100%relative humidity(in water droplets).3.By studying the community of endophytic fungi in the phloem of Sorbus,the types of phloem fungi were abundant.A total of 13 fungi were isolated,of which 12 species were semi-known fungi and 1 were zygomytes.Among them,the dominant species were Paecilomyces sp.,Penicillium sp.,Trichoderma longibrachiatum and Trichoderma harzianum.The isolation rates respectively were 16.8%,21.3%,13.0%and 12.7%.4.In the selected plate-to-cockroach test of six biocontrol bacteria and pathogens,Trichoderma longibrachiatum had the strongest inhibitory effect on pathogenic mycelium with an inhibition rate of 70.34%,followed by Trichoderma harzianum,49.58%and Trichoderma viride,46.52%respectively,all three have reached more than 40%.Trichoderma harzianum,Trichoderma longibrachiatum and Trichoderma viride which could inhibit the pathogens effectively were screened and selected according to the indicators such as antibacterial rate,antagonistic coefficient and degree of coverage.5.The culture filtrates of three kinds of biocontrol bacteria had great differences in the inhibition of mycelial growth and spore germination of Pinus sylvestris pathogen mycelium.The highest inhibition rate of mycelium was Trichoderma harzianum,when the content of filtrate in culture was 50%and the inhibition rate was 70.21%.The Trichoderma longibrachiatum has the strongest inhibitory effect on spore germination and the germination rate of 24 hours was suppressed to 58%.