Abstract:

The strain 1X1Y was isolated from the rhizosphere soil of healthy potato，and it was identified as Bacillus velezensis by morphological characteristics，physiological and biochemical characteristics and multi-gene sequence analysis. The antagonistic strain was screened and its antibacterial activity was verified by the plate confrontation culture method and the inhibition zone method. The culture solution could significantly inhibit the growth of Streptomyces acidiscabies and S. turgidiscabies，and the diameter of inhibition zone was（34.92 ± 0.90）and（35.14 ± 1.56）mm. The relative control effect on scab was 57.52%. It could also significantly inhibit the growth of Phytophthora infestans，Rhizoctonia solani，Alternaria alternata and Colletotrichum coccodes，with inhibition rate of 56.44%-71.47%. The key genes for the synthesis of antimicrobial substances in strain 1X1Y were detected by multiple pairs of specific primers. The strain 1X1Y contains 10 key genes for the synthesis of antimicrobial substances，such as srfAB，bmyB，fenD，bacA，ituC，bioA，beaS，dhbA，dfnA and mycB. The biocontrol and growth-promoting characteristics of extracellular hydrolase，resistance substance content and defense enzyme activity were determined by extracellular enzyme and siderophore production medium，transparent circle method，blood plate，oil discharge and ultraviolet spectrophotometry. The strain 1X1Y could secrete protease，β-1,3 glucanase，cellulase，siderophore，lipopeptide and other antibacterial related substances，and could form a complex biofilm structure，which was conducive to colonization in the rhizosphere. At the same time，the plant resistance was enhanced by increasing the soluble protein content of potato and the activities of PAL and PPO defense enzymes and reducing the content of malondialdehyde. In addition，strain 1X1Y has both nitrogen fixation and ACC degradation activity，which can dissolve calcium phosphate，iron phosphate，aluminium phosphate，soybean lecithin，egg yolk lecithin，magnesium carbonate，zinc oxide and other insoluble compounds，and significantly increase potato plant height，chlorophyll relative content，stem diameter and yield per plant.

Key words: potato, common scab, Bacillus velezensis, biological control, growth promoting effect