Pseudostellaria Heterophylla Continuous Cropping Root Rot Disease Physiological And Biochemical And Micro Ecological Mechanism

Pseudostellaria heterophylla was cultivated in Shibing County of Guizhou Province more than twenty years.The quality and quantity of Pseudostellaria heterophylla severely declined by Pest,especially root rot disease,on the bases of shortage lands and cultivation continuously.Therefore,the aggravating obstacle of continuous cropping,and frequently diseases of P.Heterophylla has become an urgent problem on production.The study aimed to identify root rot pathogen of P.heterophylla,recognize physiological-biochemical characteristic of P.heterophylla,such as C,N metabolism,plant defense enzyme and relatively researches of soil nutrient,economic traits and soil microbiota on continuous cropping.The result preliminarily revealed physiological,biochemical and micro ecological mechanism of root rot disease on P.heterophylla with theory for controlling root rot pathogen.The following are achievements:1.The pathogen identification of root rot disease on P.heterophyllaThe suspected pathogen was isolated from infected P.heterophylla and verified in according to the Koch's Low.Based on the analysis of morphological characteristics and DNA sequence,the pathogen was identified as Fusarium oxysporum.2.Soil nutrient,economic traits of P.heterophylla.With continuously cropping,the root rot disease of P.Heterophylla became more serious.Its incidence has positive correlation with year of continuous cropping.As following,potassium and p H decreased,the available phosphorus increased,organic matter,nitrogen and alkali nitrogen attained the maximum in five serious years,The P.Heterophylla root economic characters(Stem weight,root weight,yield)and polysaccharide content trended to downward.3.C,N metabolismIn the same area,the contents of soluble sugar,proline and protein in the flowering stage A were totally higher than those of filling stage B,the activity of nitrate reductase in phase A was lower than that in phase B and no obviously change to chitinase activity.With continuous cropping years increasing,soluble sugar content and nitrate reductase decreased,but proline,protein content and chitinase activity increased in stage B.4.The activity of defense enzyme of P.heterophyllaBefore infected,the activity of leaf defense enzyme did not apparently change.However,the root defense enzyme activity changed after infected disease.The activities of PPO,POD,CAT and PAL decreased and the activities of SOD increased.5.Change of Soil microbiotaWith years increasingly of continuous cropping,the number of cultivable fungi was increasing,and four dominant fungi were Penicillium,Fusarium,Aspergillus and Mucor.The number of culturable bacteria had increasing.The dominant bacteria were respectively Bacillus,Arthrobacter,Flavobacterium,Sphingobacterium,etc.The number of cultivable actinomycetes did not changed obviously in the first four years,and increased sharply in the fifth year.There were six dominant bacteria,including Streptomyces roseochromogenes,S.flavogriseus,S.niveus,S.cellulosae,S.zaomyceticus,S.olivochromogenes.But with years increasingly of continuous cropping,the incidence and disease index increased gradually.The disease incidence index were the positive correlation with the number of soil fungi.