Evaluation Of Soft Rot Resistance Of Konjac Germplasm Resources And Screening Of Antagonistic Actinomycetes

Konjac soft rot is a bacterial soil-borne disease,which can infect the leaves,petioles,bulbs,roots and other parts of konjac when the disease occurs,affecting the normal growth and development of plants,and even leads to the failure of konjac harvest,which seriously restricts the development of konjac industry.At present,the prevention and control of konjac soft rot mainly relies on chemical control methods,but the long-term application of chemical fungicides will lead to drug resistance of pathogenic bacteria,and will also produce chemical pollution,drug residues and other issues.Therefore,breeding new varieties of konjac resistant to soft rot is the most effective way.In addition,biological control technology has the characteristics of high efficiency and safety,non-toxicity and no residue,among which antagonistic actinomycetes are considered to be an efficient new way to replace traditional chemical fungicides.In this study,the high-quality materials with high resistance to soft rot were screened by collecting the germplasm resource materials of konjac and evaluating the disease resistance,and the relationship between the activity of defense enzymes and the resistance of soft rot was preliminarily explored.Then,screening for actinomycetes with good antagonistic activity against konjac soft rot bacteria can provide new antagonistic strain resources for the prevention and control of konjac soft rot.The main findings are as follows:1.The classification status of pathogenic strains MY-30 and MY-36 was determined.Two strains were identified from micromorphology,culture characteristics,and molecular level,MY-30 and Pectobacterium carotovorum subsp.The carotovorum strain has the highest homology,reaching more than 95%,and MY-36 has the highest homology with the D.fangzhongdai strain,reaching more than 96%.2.The anti-soft rot level of the leaves,petioles,bulbs and irrigation root inoculation of 41 konjac germplasm resource materials was identified,and no immune materials were found,and the anti-susceptibility grading results of different inoculation methods were different.There was a significant correlation between plant root inoculation and the results obtained by leaf inoculation.It shows that the resistance evaluation of konjac material to soft rot cannot use petioles and bulbs as the sole basis,and leaf inoculation can be used as a certain reference,and the resistance evaluation of root inoculation is combined to determine the resistance of konjac materials.3.The content of defense enzymes after the infestation of soft rot bacteria in the leaves of the two resistant konjac materials was determined,and the results showed that after inoculation of the bacteria,there were differences in the activity trends of the five enzymes of defense enzymes PPO,CAT,POD,SOD and PAL,but the changes of the same enzyme of high resistance and high sensitivity materials were about the same.The ability of high-resistance materials to induce the generation of 5 defensive enzyme activities is stronger,and the activities of high-resistance materials PPO,POD,SOD,and PAL enzymes are always higher than those of high-sensitivity materials at different time periods.Surface defense enzyme activity can be used as an analytical basis for evaluating the ability of konjac to resist soft rot.4.The double-layer medium method obtains 26 strains with antagonistic activity by preliminary screening,and the bacteriostatic circle diameter of 6 strains on konjac soft rot is more than 30 mm,and the bacteriostatic effect of strain F188 on konjac soft rot is the strongest,the diameter of the bacteriostatic circle reaches 57.09 mm,and the bacteriostatic circle is completely transparent.Strains F188 and F194 both have a broad spectrum of bacteriostatic properties.Actinomycete F188 fermentation broth and fermentation filtrate can reduce the degree of konjac bulb rot,and the fermentation stock of strain F188 can effectively reduce the incidence of soft rot in konjac seedlings.Strain identification was performed by micromorphology,culture characteristics,and16 Sr DNA sequence analysis,and strain F188 was Streptomyces virginiae.