Identification And Biological Characteristics Of The Pathogen In Phytophthora Blight Of Fig

Phytophthora blight of fig caused by Phytophthora palmivora is one of the important diseases of fig.The symptom samples were collected from fig orchards in Guanting town,Hefei,Anhui,and 2 strains were isolated on diseased fruit.Through morphological observation and molecular biology identification of pathogenic fungi was identified,biological characteristics and bioassay of effective fungicides were conducted,determine the appropriate environmental conditions for the growth of Phytophthora palmivora and determine the inhibitory effect of 4 fungicides on the pathogen were determined.The results of this study provide a reference for the occurrence,prevalence and prevention of fig Phytophthora blight of fig in orchard.The main findings are as follows:1.Isolation and identification of pathogenic fungiThe pathogenic fungi were isolated by the method of plant tissue separation,The morphological observation of pathogenic fungi showed that hyphae are colorless and transparent,without diaphragm,relatively thin,part of the irregular expansion,Sporangia is ovoid,round or inverted pear shaped,and measured 42 to 71 ×32 to 39?m,with obvious papillae,often single papillae,sometimes double papillae,and easy to shed.The sporangiophore is short and branching in a simple concentric manner.Broken sporangia can release a large number of zoospores.,The chlamydospores produced in culture were spherical and brown,measured 26.9~42.4?m.Clustering analysis of cytochrome C oxidase subunit I(COX I)gene was performed.The phylogenetic tree of Phytophthora showed that the isolated strains were in the same branch with several Phytophthora palmivora strains(HQ261280,HQ708256,HQ261382 and AB688276)and the sequence homology was 99%,and the morphological observation showed that the pathogen was Phytophthora palmivora.2.Biological characteristics of pathogenic fungiThis test determined the optimal growth medium,optimum mycelial growth and spore production quantity temperature,p H value,lethal temperature of pathogenic fungi and the utilization degree of pathogenic fungi to different carbon sources and nitrogen sources.The results show that the optimal culture mediums for pathogenic fungi was oat and maize medium medium.The mycelium of pathogenic fungi grew well between 25?-30?and the optimum temperature was 28?.Under 47 ? water bath after 10 min,pathogenic fungi can't grow.The optimum p H was 6,the dry weight of mycelium reaches its maximum.pathogenic fungi grew best in medium with peptone as nitrogen source,and mycelium dry weight was the largest.The growth was best in the culture medium with fructose as the carbon source,and the dry weight of mycelium was the largest.The growth was worst in the culture medium without carbon source,indicating that the pathogen had certain requirements for carbon source.3.Toxicity determination of effective fungicides of pathogenic fungiAccording to growth rate method and the toxic medium method,the inhibition of metalaxyl-m,dimethomoph,pyraclostrobin,azoxystrobin on the pathogenic fungi.The results showed that metalaxyl-m had the best inhibitory effect on mycelia growth,followed by dimethomoph with EC50 value of 0.1853 ?L/m L and 0.4704 ?L/m L,respectively;The inhibition effect of pyraclostrobin and azoxystrobin on mycelium growth was poor,the EC50 values were 3.2262 ?L/m L and 8.7680 ?L/m L,respectively.Inhibition of sporangia formation of pathogenic fungi is also the best effect of metalaxyl-m.The EC50 value is 0.0247 ?L/m L,followed by dimethomoph with an EC50 value of 0.0300?L/m L.The inhibition effect of pyraclostrobin and azoxystrobin on sporangia formation was poor,the EC50 values were 0.5286 ?L/m L and 5.9973 ?L/m L,respectively.,Inhibition of zoospore release,dimethomorph has the best effect,with EC50 value of 0.3081 ?L/m L,followed by metalaxyl-m,and EC50 value of 0.3947 ?L/m L.The The inhibition effect of pyraclostrobin and azoxystrobin are more effective The EC50 values were 3.6848 ?L/m L and 4.7704 ?L/m L.