| Plant growth-promoting rhizobacteria is one kind of bacteria which can benefit the growth of plant through various direct or indirect effects,also called PGPR.They are mostly N-fixing bacteria,P-releasing bacteria and K-releasing bacteria.In the early time,we isolated and purified a number of good N-fixing bacteria,P-releasing bacteria and K-releasing bacteria from the woodland of Eucalyptus,Podocarpus macrophyllus and Acacia crassicarpa.The tested strains were classified and identified by 16S rDNA-Sequential Analysis,and inoculated on Eucalyptus for seedling and afforestation test with randomized block design.A number of strains which have good growth-promoting effect had been screened out.The test provided realistic foundation and guidance for the sustainable forestry development of Eucalyptus and large area of inoculated afforestation.14 Strains which involved in 16S rDNA-Sequential Analysis were blasted in NCBI,they can be divided into four different genus initially:the five strains Nd, 9K,4K,4Kv,14K belong to Acinetobacter;the three strains N6,Nc,N1 belong to Bacillus;the five strains K1,40K,30K,6P,P1 belong to Staphylococcus;only N5 belong to Anaerococcus.Considered the results of seedling and afforestation test, the better were six of fourteen tested strains inoculated Eucalypus grandis×E.urophylla GL9, they were N1,N6,9K,NC,40K,14K.The tree heights of various treatment groups were higher 13.95%-32.21% than the control group, the basal diameters were higher 32.49%-54.94% than the control group.Compared the effect of growth-promoting which be screened out six good PGPR between N-fixing bacteria(Nc,N6,N1) and K-releasing bacteria(40K,14K,9K), T test results showed that the effect of growth-promoting of N-fixing bacteria significantly superior to K-releasing bacteria.From the inoculation test results of 8 different mixed strains N-fixing bacteria and P-releasing bacteria from Vegetable research base,the four fixed strains N1+P,N1+L2+P,L2+P,4Y+L2+P showed a better inoculation effect of growth-promoting.The fixed strains N1+P,N1+L2+P,L2+P,4Y+P,4Y+L2+P showed a better inoculation effect of growth-promoting significantly than the single strain P.The fixed strains N1+P which from the Eucalyptus woodland showed a better seedling (tree)height significantly than the fixed strains 4Y+L2 which from the Podocarpus macrophyllus woodland.From the results of Eucalyptus grandis×E. urophylla GL9 inoculated with 8 different N-fixing bacteria in Guangxi Forestry Research Institute,the 5 strains D7+4Y,H6+L2,H6,D7,L2+4Y showed a better growth-promoting effect of inoculation.The three fixed strains D7+H6,H6+L2,4Y+H6 showed a better growth-promoting effect significantly than the single strain H6 in afforestation test.But the other fixed strains D7+L2,D7+4Y,D7+H6 did't show a better growth-promoting effect significantly than the single strain D7.Contrast experiments of Eucalypus grandis×E.urophylla GL9 and E. urophylla×E. grandis 3229, which both inoculated by fixed strain 4Y+L2, the results showed that:the tree height and basal diameter of inoculation group were both higher than the control group.The basal diameters of GL9 and 29 were higher 7.72% and 20.18% respectively than the control group, the seedling heights of GL9 and 29 were higher 5.02% and 16.40% respectively than the control group in seedling test.The basal diameter of GL9 and 29 were higher 8.04%-35.93% and 4.9%-56.20% respectively than the control group, the tree height of GL9 and 29 were higher 35.74% and 4.47%-72.22% respectively than the control group in forestation test.The effect of inoculation of 29 significantly superior to GL9 in the seedling test and the first afforestation test, while the effect was on the contrary in the second afforestation test. In addition, the two Eucalyptus clones inoculated with N-fixing bacteria also showed high resistance in the environment, trees can resume the growth rapidly after suffering from the serious damage of Leptocybe invasa Fisher et La Salle. |
PDF Full Text Request