高寒草甸嵩草、珠芽蓼根际优良植物根际促生菌的分离筛选及促生特性研究

为从高寒草甸优势牧草(蒿草、珠芽蓼)根际筛选具有优良促生特性的植物根际促生菌(PGPR),探寻其根际分布规律,并为后期生产应用提供支撑。采用选择性培养基法筛选根表土(RS)、根表面(RP)和根内(HP)细菌,用点接种法在选择培养基(Pikovaskaia's 培养基、蒙金娜、无氮培养基)中复筛具溶磷、固氮特性菌株;采用钼蓝比色法、气相色谱法和高效液相色谱法分别测定菌株溶磷量、固氮酶活性和分泌植物激素PHs:吲哚乙酸(IAA)、赤霉素(GA₃)、反式玉米素(t-Z)]含量。结果表明:共筛出细菌68株,复筛出溶磷固氮PGPR 43株;其中,溶解无机磷菌17株(溶磷量:9.39~94.79 μg·mL^-1),溶解有机磷菌22株(溶磷量:10.37~72.82 μg·mL^-1),固氮菌30株固氮酶活性:3.79~3193.07 nmol (C₂H₄)·h^-1·mL^-1];分泌IAA菌26株(IAA含量:0.24~69.98 μg·mL^-1),分泌GA₃菌32株(GA₃含量:0.34~68.87 μg·mL^-1)和36株分泌t-Z菌(t-Z含量:0.11~47.59 μg·mL^-1)。植株根际促生菌PGPR均表现出根表面RP区细菌数显著高于根表土RS和根内HP区,珠芽蓼根际筛选出的PGPR多于嵩草根际;蒿草PGPR溶解有机磷能力强于珠芽蓼根际PGPR,但溶无机磷PGPR数目和能力相反。分泌植物激素PHs菌株在能力和数量上均表现出t-Z>GA₃>IAA的趋势。因此,优良溶磷菌(ZNRS2、SNRP2、ZKHP3、ZKRP1),优良固氮菌株(SKRP2、SNHP1、ZNRS3)和优良产植物激素PHs菌(SKHP3、ZNHP2、ZKRS2、ZKRP1、ZKRP2)可用于后期微生物肥料制作和相关研究,其中ZKRS2的促生功能较多,可进行深入挖掘。

Isolation,screening, and growth-promoting characteristics of plant growth promoting rhizobacteria in the rhizosphere of Kobresia myosuroides and Polygonum viviparum in alpine meadow pasture

The aim of this study was to screen the rhizosphere of the dominant species in an alpine meadow (Kobresia myosuroides and Polygonum viviparum), for plant growth promoting rhizobacteria (PGPR) with excellent growth-promoting properties. The rhizosphere distribution pattern was also explored for later production and applications. We screened bacteria from root surface soil (RS), the root surface (RP), and roots (HP) by the plate coating method, then re-screened bacteria in selective media containing phosphorus (Pikovskaya medium, Mengjinna medium, nitrogen-free medium) by spot inoculation of nitrogen-fixing strains. For all strains, we determined phosphorus solubilization, nitrogenase activity, and secretion of phytohormones (indoleacetic acid, IAA; gibberellin, GA₃; trans-zeatin, t-Z). Then, strains were re-screened by molybdenum blue colorimetry, gas chromatography, and high performance liquid chromatography. The first screening step yielded 68 bacterial strains, and then the next step reduced the number to 43 nitrogen-fixing phosphatase-active PGPR strains. Among those 43 strains, 17 were able to dissolve inorganic phosphorus (phosphorus content: 9.39-94.79 μg·mL^-1); 22 were able to dissolve organic phosphorus (phosphorus content: 10.37-72.82 μg·mL^-1); 30 were able to biologically fix nitrogen nitrogenase activity: 3.79-3193.07 nmol (C₂H₄)·h^-1·mL^-1]; 26 secreted IAA (0.24-69.98 μg·mL^-1); 32 secreted GA₃ (0.34-68.87 μg·mL^-1) and 36 secreted t-Z (0.11-47.59 μg·mL^-1). There were significantly more PGPR in the RP area than in the RS and HP areas, and more PGPR in the rhizosphere of P. viviparum than in that of K. myosuroides. The ability of PGPR to dissolve organic phosphorus was greater in the K. myosuroides rhizosphere than in the P. viviparum rhizosphere. The number of PGPR was inversely related to the ability to dissolve inorganic phosphorus in the rhizosphere. In the strains that secreted phytohormones, the most abundant was t-Z, followed by GA₃ and then IAA. The main phosphate-solubilizing strains (ZNRS2, SNRP2, ZKHP3, ZKRP1), nitrogen-fixing strains (SKRP2, SNHP1, ZNRS3), and phytohormone-producing strains (SKHP3, ZNHP2, ZKRS2, ZKRP1, ZKRP2) could be used for microbial fertilizer production and related research. The strain ZKRS2 had the strongest growth promoting effect, and should be studied in more detail.