Study On Relationship Between Fire Blight And Valsa Canker Of Korla Pear

Fire blight is a devastating bacterial disease caused by Erwinia amylovora,which has a great impact on the local fragrant pear industry.Pear Valsa canker is common in pear orchards in Korla,Xinjiang,and has become an important factor affecting the healthy development of local fragrant pear industry.This study comprehensively analyzed the correlation between the two diseases through the analysis of the relationship between the occurrence degree of fire blight and pear Valsa canker in the field,and the investigation of the coexistence and interaction of the two pathogens,and the analysis of the infection relationship of the two pathogens under the condition of cross inoculation.This provides a theoretical basis for the comprehensive prevention and control of the two diseases.The main results are as follows:(1)The survey results of the two diseases in 16 pear orchards with different occurrence degree of fire blight in Korla area in 2021 showed that there was a moderate correlation between pear fire blight and the field incidence and disease index of Valsa canker,and the correlation coefficients were 0.63 and 0.47.(2)The detection of pear Valsa canker spots in different periods by PMA-q PCR live bacteria detection method and plate scribe verification method showed that E.amylovora were detected on 2.96% of the Valsa canker spots,indicating that E.amylovora and V.pyri can coexist on the same disease spot,but the coexistence rate was very low.(3)The observation results after the confrontation culture of the two pathogen showed that there was nutritional competition between E.amylovora and V.pyri;There was no obvious inhibition and synergy.(4)The results of cross inoculation showed that E.amylovora and V.pyri could infect the same pear branch at the same time.There was no significant difference between the mixed inoculation of two pathogens on isolated branches and the inoculation of E.amylovora first and then V.pyri and the single inoculation of E.amylovora,indicating that V.pyri had no significant effect on the expansion of fire blight.There was no significant difference in the disease spots between the isolated branches firstly inoculation with V.pyri and then inoculation with E.amylovora and single-inoculation with V.pyri.(5)The above results showed that there was no obvious inhibition and synergy between E.amylovora and V.pyri,but there was obvious nutritional competition;Due to the similarity of the incidence conditions of the two diseases,the occurrence degree of the two diseases is moderately correlated between fields,but the direct correlation between the two diseases is very small.