Isolation,Identification And Biological Characteristics Of Diaporthe Citri

Diaporthe citri is one of the most important diseases of citrus.Generally,only when the tree is injured or the growth is not good,especially when it is damaged,it is the most susceptible to infection.After the fruit damage occurring at the surface of the sand like pits,seriously affect the appearance of citrus fruit.Diaporthe citri is one of the most common and serious diseases in citrus producing areas in China,often resulting in the decline of citrus quality..This study collected in different regions of Hunan citrus growing areas of typical citrus fruit or leaf disease symptoms of Diaporthe citri.It carry out these study that isolated and identified the pathogens.Based on this,biological characteristics of the pathogens was studied,and then virulence evaluation experiment were done,AS a result.these provided theoretical basis for the control of Diaporthe citri.The main results were follows:?1?In ths study,pathogenic bacteria were identified by pathogens isolation,morphological characterization and ITS sequence analysis of the sample isolated.A total of27 strains were isolated in different areas of Hunan province,and they were stored by the method of Conventional bacterial preservation.?2?The results of studies on biological characteristics of 6 strains of Diaporthe citri showed that the optimum media for the growth of 6 strains included V8 fruit and vegetable culture medium and oat medium,Temperatures for mycelium growth of each tested isolate ranged from 10?to 35?,the favorable temperature value was from 26?³0?.The lethal temperature was 40?.The ranges of pH for mycelium growth of the tested isolates were the same from 3 to 12.The optimal pH value was from 6⁹.The lethal pH of the acid condition was 2 and The lethal pH of the alkaline condition was 13.light and dark was the best for mycelial growth.The favorable nitroge sources of mycelial growth of the tested isolates were yeast extract,beef extract and peptone.The optimum carbon sources of mycelium growth were sucrose.?3?Diaporthe citri is one of the diseases widespread and seriously harmful in the citrus producing area in china,and often results in the decreased quality of citrus..In order to screen effective fungicides for Diaporthe citri,and then screened effective fungicides from prochloraz,difenoconazole,carbendazim,fosetyl-aluminium and manc ozeb compound agent,mancozeb to Diaporthe citri according to their inhibition to m ycelial growth rate.The bacteriostatic effect of fungicides from strong to weak:proch loraz,difenoconazole,carbendazim,fosetyl-aluminium and mancozeb.The results showed that 25%prochloraz SC was the highest toxicity on the Diaporthe medusaea with E C₅₀ value of 0.099?g/ml.?4?The 27 strains was amplified and sequenced,the length of ITS sequenced and the length of?-tubulin sequenced were 500bp.The resulting fragments were sent to Shanghai for sequencing,The sequenced ITS and?-tubulin of 27 strains were aligend with related sequences downloade from Genbank respectively with bioinformatics softwares.Different citrus pathogen strains between Diaporthe citri caused by the difference of genetic diversity.However,this difference was not significantly related to the source of isolates.