Analysis On The Relationship Between The Valsa Canker Of Korla Fragrant Pear Occurrence And Nutrition、Resistance Enzyme Activity

Korla fragrant pear is one of the characteristic fruit trees in China.In recent years,the Valsa canker of Korla fragrant pear is extremely serious,which has become an important factor restricting the development of Korla fragrant pear.A large number of studies have shown that Valsa canker are weak pathogenic bacteria,and the pathogenicity depends on the health status of the tree.Therefore,in this study,from the point of view of mineral nutrition,through collecting and isolating rotting bacteria,we set up different concentration gradient N,P,K medium.To study the effect of inorganic element N、P、K on the growth of Valsa canker colony,to study the correlation between soil nutrients and the occurrence of Valsa canker,and to explore the correlation between the mineral elements of tree body and the occurrence of Valsa canker of Korla fragrant pear.In order to provide the theoretical basis for the prevention and control of Korla fragrant pear rot disease,the effects of the occurrence of rot disease on the activity of resistance enzymes in trees were studied.The main results were as follows:(1)In this paper,13 monosporal isolates were obtained from pear orchard of Tarim University.By observing and comparing its culture shape,it was divided into three groups: orange-red sporulation group,light green sporulation group and gray-white refractory sporulation group;in vitro,the pathogenicity of each isolate was determined,and different isolates were able to cause disease.But there were differences in pathogenicity.The pathogenicity of light green sporulation group and gray white difficult sporulation group was stronger,and orange color sporulation group had the worst pathogenicity.(2)By setting the medium with different concentrations of inorganic elements,the effects of the inorganic element N P K on the growth of the rotting colony were investigated.The results showed that the different concentrations of N P K had an effect on the growth of the colony,which was manifested as the increase of N content.With the increase of P concentration,the growth rate of bacteria increased first and then decreased.With the increase of K concentration,the growth rate of bacteria increased first and then decreased.(3)Through the investigation of the incidence degree of different pear orchards and the determination of soil nutrient content and mineral element content of tree body,it was found that,The incidence of Korla fragrant pear Valsa was negatively correlated with soil organic matter,soil K content and tree K content,and positively correlated with N/K、P/K ratio of soil and tree,that is,the higher the ratio of N/K、P/K,the more serious the disease was.(4)The experimental results showed that the five enzymes PAL,SOD,POD,CAT and PPO all participated in the physiological activities of defense against rot and pathogenic bacteria of Korla fragrant pear.In different disease severity,the activity of five enzymes was different,and the activity of SOD first appeared as the degree of disease increased.After the increase,the activity of POD increased and theactivity of CAT first decreased and then increased.PAL increased first and then decreased,and PPO decreased.(5)There was a significant positive correlation between K content and polyphenol oxidase in the phloem of branches.The increase of K content was beneficial to increase the activity of polyphenol oxidase.