Isolation And Identification Of Growth-promoting Rhizobacteria And The Growth Promotion To Potato Rapid Propagation Plantlet

Rapid propagation is a common method of propagation in potato production practice and scientific research.However,rapid propagation needs repeated subculture,which often leads to the decrease of the growth speed of rapid propagation plantlets,the decrease of the number of growth nodes,the underdevelopment of roots and the weakness of stems.This led to the extension of the reproduction cycle of the rapid propagation plantlets,the number of propagation and the survival rate after transplanting are reduced,and finally resulted in the low yield of the microtuber and increased production cost.Plant rhizosphere promoters colonize plant rhizosphere system which can stimulate plant growth,alleviate biological and abiotic stress,and increase yield.It has great application potential in plant rapid propagation.However,there are few reports about the effects of inoculated microorganisms on the growth of potato rapid propagation plantlets.In this study,potato rhizosphere soil in Wuchuan and liangcheng rhizosphere soil of Inner Mongolia were collected,and the rhizosphere bacteria were isolated and cultured based on the selective medium and the coating and scribing method.The isolated strains were preliminarily classified and identified based on homology analysis of 16S rRNA gene sequence;the strains were inoculated into tissue culture bottles and transplanting potato plantlets and observe the effects on the growth of potato plantlets;the 10 strains which had the most significant effects on the node number,stem diameter and root length of potato rapid propagation plantlets were selected to analyze the growth promoting characteristics of 10 strains by spectrophotometry and other techniques.The compound bacteria were constructed by culling them one by one.The main results and conclusions are as follows:1.A total of 134 strains of bacteria were isolated,which belonged to 34 genera,the number of Bacillus is the largest,accounting for 22.31%of all strains.Among them,93 strains were isolated by inorganic phosphorus medium,including 25 genera.Streptomyces,bacillus and arthrobacteria were dominant bacteria,accounting for 22.58%,20.43%and 9.68%of inorganic phosphorus dissolving strains,respectively.29 strains were isolated by nitrogen fixing medium,including 15 genera,Rhizobium was the first dominant bacteria,accounting for 27.59%of nitrogen fixing bacteria;12 strains of bacteria were isolated from organophosphorus medium,including 4 genera.Bacillus is the first dominant genus,accounting for 58.33%of the organophosphorus bacteria.2.Effects of single bacteria on the growth of potato rapid propagation plantlets:Inoculation analysis of 70 strains was completed.48 strains of bacteria increased the plant height by 0.3%-32.69%,39 strains increased the root length by 1.04%-49.48%,51 strains increased the node number by 1%-34.75%,46 strains increased the stem diameter by 0.9%-33.33%,42 strains increased the root dry weight by 3.75%-397.31%%,36 strains increased stem dry weight by 6.67%-66.67%;17 strains promoted plant height,root length,node number,stem diameter,root dry weight and stem dry weight.3.Effects of single bacteria on the rapid propagation potato plantlets planted in pot:The inoculation analysis of 70 strains was completed,among which 51 strains increased the plant height by 0.43%-54.28%compared with the control strains without inoculation,44 strains increased the node number by 1.62%-57.31%,20 strains increased the root dry weight by 2.65%-105.3%,59 strains increased the stem dry weight by 0.88%-186.73%.36 strains increased the number of seed tubers by 20%-60%,44 strains increased the average weight of a single seed tuber by 1.62%-198.87%;5 strains promoted the increase of plant height,node number,root dry weight,stem dry weight,seed tuber number and average weight of a single seed tuber;39 strains promoted the increase of seed tuber number and weight.4.Growth promoting characteristics of strains:All 10 strains have the ability of producing iron carrier and IAA,and the strongest related abilities are MP16(IAA concentration in the culture solution can reach 26.75 mg/L)and W39(D/d ratio of orange halo diameter to colony diameter is 2.53),respectively;strains T1,T2,N20,L3,L2 and MP16 all have the potential of nitrogen fixation,inorganic and organic phosphorus removal,among which T2,L3,L2 and MP16 also have the ability to produce ACC deaminase;T1,T4,N2-1,L3 and MP16 also have the ability to produce NH3.5.The influence of complex bacteria on the rapid propagation of potato plantlets:Based on the influence of different combinations of 10 strains of bacteria on the growth index of the rapid propagation of potato plantlets,a dominant compound bacteria agent composed of 6 strains(T1,T2,N2-1,N20,L3 and L2)was preliminarily obtained.