Identification Of Needle Blight Of Picea And Abies And Screening Of Biological Strains And Fungicides

Picea Dietr and Abies Mill are evergreen woody plants with the beautiful tree shape,which were widely distributed in China,as landscaping tree species,as well as an mountain afforestation tree species and an important timber tree species.They are cultivated in large areas in cities and mountains in China.Therefore,the occurrence and damage of spruce and fir diseases have been gradually received the attention from the garden and forestry departments.In 2018,we found a one new leaf disease of on spruce and fir was found in Maoershan Experimental Forest Farm of NorthEast Northeast Forestry University.In this paper,the collection of disease specimens,morphological identification.Koch’s Postulates,molecular characteristics,biological characteristics,screening of biological antagonistic strains and screening of chemical pesticides were studied.So,it is important to provide a basis for the prevention and control of the disease.The specimens of the pathogen of Spruce Needle Blight were isolated and purified.The spruce leaf blight disease specimens were identified by pathogen morphology and ITS gene sequence comparison to confirm that the Spruce Needle Blight pathogen was Rhizosphaera kalkhoffia Bubak.The pathogens of Fir Needle Blight were isolates,purified and determined in pathogenicity,and RP1 and RP2 strains was determined as the causative pathogens of Fir Needle Blight.Morphological identification and ITS gene sequence comparison confirmed that the pathogen RP1 of fir leaf blight is pine root ball Rhizosphaera pini(Corda)Maubi.Another pathogen RP2 is Sydowia polyspora Bres.Fir Needle Blight is the first disease discovered in China.Rhizosphaera pini(Corda)Maubi.is a new record species in China.The biological characteristics of showed that the optimal growth temperature of RP2 Sydowia polyspora Bres.was 18℃;the growth of pathogenic mycelium had no strict requirements on the environmental pH;And glucose was the optimal growth of carbon source,yeast extract as nitrogen source.The pathogenic spores have strong germination ability,which can germinate in a variety of nutrient solutions among the pH value 4.5-9.2.with the fast germination rate at 15-20℃.Combined with the antagonism test with biocontrol potential.5 strains of biocontrol produced the inhibitory effect on the mycelial growth of Sydowia polyspora Bres.Two Bacillus strains with excellent inhibitory effect on RP2 mycelium were obtained from the studies.Among them,Bacillus methylotrophicus numbered BA-3 had strong and stable inhibitory effect,with the continuous bacteriostatic rate as 100%.When the fermentation liquids of the two Bacillus as BA-1 and BA-3 at 20%concentration had better effect on the germination inhibition of the pathogen RP2 spores,and the antibacterial activity of the two strains of Bacillus could be maintained at-4℃ for at least 40 days.Six kinds of low-toxic fungicides were selected to conduct the bacteriostatic test on RP2.The results showed that carbendazim and thiophanate-methyl had excellent inhibitory effects on the growth of the pathogen RP2 mycelium,for which EC50 was 0.07mg/L and 0.17mg/L respectively.Among them,carbendazim has a good ability to inhibit the germination of pathogenic spores.At a concentration of 100mg/L,it can still produce a circle of inhibition with 21 mm in diameter.As result,carbendazim has a good inhibitory effect on spore germination and mycelial growth of pathogens,and carbendazim can be selected for prevention and control.