Screening And Mechanism Of Inducers Of Rhizoma Rhizoma Rhizoma Rhizoma Rhizoma Rhizoma

Pseudostellaria heterophylla,belongs to Caryophyllaceae,is widely used in the field of medicine and health care products for its functions of invigorating spleen and moistening lung.Guizhou Province is one of the main production areas of Pseudostellaria heterophylla in China,and beause of the large-scale planting all year round,leaf spot has become the main fungal disease of Pseudostellaria heterophylla.Leaf spot has many pathogens,and the common chemical agents are difficult to sovle this issue,otherwise,exploring new methods to control this disease is also difficult.At present,plant disease resistance inducers are widely used in variety of plants or crops diseases’ s controlment because of their broad-spectrum,safety,sustained effect and other advantages.The purpose of this study is to screen the inducers which can induce resistance of Pseudostellaria heterophylla leaf spot,and to study the resistance mechanism of inducers from the aspects of disease control effect,physiological index changes of induced resistance,and the effect on the community structure of fungi in the phyllosphere.This study can provide a new idea for the green control of Pseudostellaria heterophylla leaf spot,and lay a practical and theoretical foundation for further research.The main results are as follows:1.Combined with morphological characteristics and phylogenetic tree based on ITS,LSU,TEF,SSU,GAPDH and RPB2 gene sequences,the pathogen,which has been isolated from Pseudostellaria heterophylla leaf spot in Shibing county was identified as Alteraria tenuissima.The results of indoor bacteriostatic test showed that Brassinolipid and Hypersensitive protein had no significant effect on the mycelial growth of A.tenuissima within the tested concentration range among the seven kinds of inducers tested,Oxalic Acid had no significant inhibitory effect at the concentration of 0.1～0.8 g/L,the other inducers could inhibit the growth of A.tenuissima,but the bacteriostatic rate was less than 50%.Brassinolide and 0.2～0.4 g/L Oxalic Acid had no significant effect on the spore germination of A.tenuissima in the range of tested concentrations,and other inducers had no significant effect on the spore germination of A.tenuissima at a lower concentration.2.The results of field control effect test showed that the seven inducers had certain control effect on leaf spot of Pseudostellaria heterophylla in the tested concentration range.The best control effect was 0.4 g/L Oxalic Acid and 1 g/L Brassinolideand their induced resistance effect up to 72.69% and 70.18% respectively in 10 days after the last application,and their induction duration were among 20～35 days.The results showed the single weight,root length and 100 seed weight of Brassinolideand treatment were significantly higher than those of CK,and the dry weight and single weight of Oxalic Acid treatment were significantly higher than those of CK.The effects of Oxalic Acid and Brassinolideand on the growth of Pseudostellaria heterophylla seedlings were studied by pot experiment,the results showed that Oxalic Acid significantly increased the plant height,stem diameter,fresh weight and dry weight of Pseudostellaria heterophylla seedlings,while Brassinolideand significantly increased the number of branches,fresh weight and dry weight of it.3.Several physiological and biochemical indexes related to disease resistance of Pseudostellaria heterophylla leaves were determined by inducing and inoculating pathogenic bacteria.The results showed that Brassinolideand and Oxalic Acid treatments increased the contents of soluble protein and chlorophyll,decreased the contents of Malondialdehyde(MDA),and induced improvement of activity of Peroxidase(POD),Superoxide dismutase(SOD),Polyphenol Oxidase(PPO)and Phenylalanine Ammonia Llyase(PAL),and increased the content of total phenols and flavonoids.The results of high-throughput sequencing showed that the application of inducers could affect the structure of the fungal community,reduce the content of Alternaria and Phoma,and increase the content of some beneficial genera such as Cladosporium and sarocladium.α diversity analysis showed that the treatment of inducers could increase the diversity and richness of the fungal community so as to reduce the occurrence of disease.