Study On The Biological Characteristics Of The Single Ascospore Stains Of Valsa Ceratosperma Sexuality And The Pathogenicity Of The Asexual Progenies

Apple tree Valsa canker was caused by Valsa spp.,which could damage the branches,fruits and other parts of the apple tree,and it's one of diseases which could cause serious harm to apple tree.The disease could make the branches dead and tree vigor became weak.When this disease occurred seriously,it would lead the yield of apple orchard and fruit quality to decline,and even destroyed the orchard.In recent years,the disease in Chineses apple producing areas occurred generally,which caused serious economic losses to apple industry.Integrating existing literature has found.There are many reports on the identification of the pathogen of apple tree Valsa canker,the characteristics of Cytospora spp.and the prevention.However,there is lack of research on the characteristics of Valsa ceratosperma sexuality;whether it can form asexual progenies;its role in the epidemic of apple tree Valsa canker;its lack of relationship with the asexual type.Therefore,this research aims at the above problems,using single ascospore isolation on the V.ceratosperma sexuality,studying the biological characteristics of single ascospores strains,the comparison between the single ascospore strains and C.spp.,and the results showed that:1 Single ascospore isolation of the Valsa ceratosperma sexualityThere were 16 ascospore single ascospore strains were obtained by single spore isolation.The single ascospore strains need 7 days would cover with petri dishes when it on the PDA medium at 25? and under dark conditions.The front and back of the colony were both milky white,the hyphae were dense.When foster continuously 30 days,it did not produce fruiting bodies.The single ascospore strains were pathogenic and the pathogenicity was significantly lower than that of the asexual strain.At about 30 days,the pycnidium was produced by the ascospore single ascospore strains in the excised branches.2 Studying on the biological characteristics of single ascospore strainsThe growth temperature of single ascospore strains ranges from 15 to 32?.The the optimum growth temperature was 25?.The single ascospore strains were able to grow under the condition of p H range from 3 to 9,the optimum growth p H was 6,and the acidic condition was more suitable for single ascospore strains' growth.Light can significantly promote the growth of the single ascospore strains.The utilization of single ascospore strains for each carbon was basically the same single ascospore strains,and glucose is the best carbon source,followed by maltose and lactose.The single ascospore strains may have a high degree of nitrogen metabolism.The species of nitrogen source have a significant effect on the growth of single ascospore strains.The single ascospore strains had the highest utilization of yeast extract,followed by beef extract and peptone;the single ascospore strains had the lowest utilization of ammonium sulfate.3 Observing on the culture characteristics of the asexual progenies were formed by single ascospore strainsThe single ascospore strains were randomly matched on the five mediums tested which cannot form perithecium.Part of the combination produced a black pycnidium at the colony junction,with pycnidium angle overflowing with the incubation time,Part of the combination did not produce pycnidium and obvious cracks at the colony junction.Single ascospore strains had the somatic incompatibility.The number of pycnidium produced on PDA medium was significantly higher than that of ABA medium,and the conidial maturity was 14 days.The pycnidiums produced by the single ascospore strains were black and spherical,the pycnidium had single or multiple chambers,and the boundaries between the chambers were not obvious.The conidia produced by the ascospore single spore had the weaker pathogenicity and germination than conidia produced by the original strain.4 Studying on the Latent Period of the different apple tree Valsa canker pathogensThe latent period of apple tree Valsa canker caused by conidia which the single ascospore strains produced was longer than that of caused by asexual strain,under the influence of various external factors.The latent period was shortened with the prolongation of moisturizing time,and the temperature had significant effect on the latent period.The latent period was the shortest at 25 ?,In the light and dark alternating conditions(12h dark + 12 h light)when the minimum latent period.