Screening Of Endophytic And Rhizospheric Potassium-dissolving Bacteria In Flue-cured Tobacco And Its Studying On Growth-promoting Effect

In order to improve the physical and chemical properties of the tobacco-growing area,promote the growth of tobacco plants,improve the quality and yield of tobacco,and solve the problem of lack of available potassium in China,in this study,the diversity of endophytic and rhizospheric bacteria in Jiyan No.9 during rosette stage was studied,and potassium-dissolving bacteria were screened to study their potassium-dissolving ability and potassium-dissolving mechanism;A pot experiment was conducted to study the effects of potassium-dissolving bacteria Y43 and H42 on the growth of tobacco seedlings,microbial quantity,enzyme activity and potassium content of soil in different seedling stages and times.It aims to provide a theoretical basis for the development and utilization of microbial fertilizers.24 strains,18 strains and 16 strains of endophytic bacteria and 11 strains,24 strains and 10 strains of rhizosphere bacteria were isolated from Wangqing,Helong and Yanji by spread plate and streak plate method.The diversity of the isolated bacteria was analyzed by phenotypic and molecular classification.The results showed that the colony morphology was inconsistent with the genetic relationship.The eight strains of potassium-dissolving bacteria obtained by the initial screening were determined to determine that the potassium-dissolving ability was determined by the liquid shake flask method.Among them,Agrobacterium Y43 and Bacillus H42 derived from the rhizospheric soil,preferably have the best potassium-relieving ability compared to other strains and controls.The highest potassium release rate of strain H42 on day 4 was 13.90 ?g·mL-1,which was 64.98%higher than the control.The highest potassium release rate of strain Y43 on day 6 was 14.13 ?g·mL-·,which was 67.13%higher than the control.The tobacco seedlings of Jiyan No.9 were used as test plants,and the roots were treated with potassium-dissolving bacteria Y43 and H42.The results showed that:(1)Potassium-dissolving bacteria Y43 and H42 have the most significant effects on agronomic traits and biomass growth of tobacco rooting period.When Y43-S treated tobacco seedlings compared with the control,the plant height,stem circumference,maximum leaf length,maximum leaf width,leaf number,chlorophyll,root length,secondary side root number,fresh weight and dry weight were increased by 89.87%,94.02%,61.47%,40.18%,60.06%,28.15%,40.28%,118.16%,210%,and 190%,better than H42-S.When Y43-3 treated tobacco plants compared with the control,the plant height,stem circumference,maximum leaf length,maximum leaf width,leaf number,root length,fresh weight and dry weight were increased by 34.17%,88.05%,31.54%,55.88%,41.75%,41.17%,91.85%,and 156.25%,the effect is better than H42-3.(2)The application of potassium-dissolving bacteria during the rooting period has significant effects on the number of soil microbes.Compared with the control,when Y43-S treated,the bacteria,actinomycetes and potassium-dissolving bacteria were increased by 627.07%,279.04%,and 1514.56%,respectively,and the fungus decreased by 39.94%,which was better than H42-S treatment.The effects of potassium-dissolving bacteria species and irrigation times on the Number of rhizosphere microbes in tobacco seedlings were different.The effect of Y43-3 treatment on rhizosphere microorganisms was better than that of H42-3.(3)The application of potassium-dissolving bacteria during the rooting period has significant effects on soil enzyme activity.When Y43-S treated,the activities of catalase,sucrase and urease were increased compared with the control by 47.06%,190.40%and 92.31%.The overall effect was better than that of applying H42-S at rooting stage.Y43-3 treatment had the best effect on soil enzyme activity.The activities of catalase,sucrase and urease were were increased compared with 54.29%,53.97%,and 81.82%,respectively,and better than H42-3.(4)The application of potassium-dissolving bacteria in the rooting period has significant effects on soil potassium and leaves potassium content.Compared with the control,when Y43-S treated,the potassium content of available potassium.slowly available potassium and leaves potassium were increased by 44.88%,52.68%,and 36.38%,respectively,and the total potassium content decreased by 2.77%.Compared with the control,when H42-S treated,the potassium content of available potassium,slowly available potassium and leaves potassium were increased by 69.74%,57.17%,and 56.30%.Y43-3 treatment had the best effect,the potassium content of available potassium,slowly available potassium and leaves potassium increased by 50.76%,27.78%and 92.41%.respectively,and the total potassium content decreased by 8.62%compared with the control.H42-2 treatment had the best effect,the potassium content of available potassium,slowly available potassium and leaves potassium increased by 46.08%.14.65%and 52.95%,respectively.The potassium-dissolving mechanism of potassium-dissolving bacteria Y43 and H42 can be used by the high performance liquid chromatography,amino acid analyzer and nuclear magnetic resonance technology to investigate preliminarily,it was found that potassium-dissolving bacteria Y43 and H42 can secrete oxalic acid,malic acid and various amino acids,and the strain H42 has a capsule outside the cell wall,while strain Y43 does not.Correlation analysis shows that with the increase of the number of days,there is a stable correlation between the organic acid secreted by potassium-dissolving bacteria Y43 and the amount of potassium.