对采自广西、云南和广东的美花石斛(Dendrobium loddigesii Rolfe)野生植株根、茎和叶内的内生细菌进行分离并测定其促生特性,采用扩增核糖体DNA 限制性酶切分析(ARDRA)与UPGMA 聚类分析相结合的方法对内生细菌菌株进行分类并确定优势属;在此基础上,对具有解磷、解钾和产生长素能力的菌株进行促生潜力评价。结果显示:从不同产地美花石斛植株不同部位共分离得到67 株内生细菌菌株,其分布呈现出组织与地区的特异性;其中,来源于广西的植株中菌株数量最多(42 株),分离自茎的菌株数量最多(34 株)。67 株内生细菌菌株可分为31 个ARDRA 簇, 经16S rDNA 序列比对鉴定为12 个属, 包括假单胞菌属( Pseudomonas )、微杆菌属(Microbacterium)、肠杆菌属(Enterobacter)、芽孢杆菌属(Bacillus)、鞘氨醇单胞菌属(Sphingomonas)、葡萄球菌属(Staphylococcus)、嗜冷杆菌属(Psychrobacter)、短波单胞菌属(Brevundimonas)、涅斯捷连科氏菌属(Nesterenkonia)、副球菌属(Paracoccus)、泛菌属(Pantoea)和沙雷氏菌属(Serratia),其中芽孢杆菌属、微杆菌属和肠杆菌属为优势属;来源于广西的植株中内生细菌的丰度与多样性均高于其他两地。在67 株内生细菌菌株中,有30 株菌株具有解无机磷和解有机磷的双重能力、22 株具有解钾能力、24 株具有产生长素能力,其中仅8 株菌株兼具3 种促生能力。组培实验结果显示:在培养基中接种1伊106 CFU·mL-1 芽孢杆菌DLB20 菌株,对株高2 ~3 cm 和3 ~4 cm 的美花石斛试管苗生长有促进作用,且更有利于株高3 ~4 cm 试管苗的生根,表明具有解磷、解钾和产生长素能力的菌株对美花石斛试管苗有一定的促生潜力。

The endophytic bacteria in root, stem and leaf of Dendrobium loddigesii Rolfe collected from Guangxi, Yunnan and Guangdong were isolated and their plant-growth-promoting activity was determined, and these endophytic bacterium strains were classified and their dominant genera were defined by means of a combination method of ARDRA and UPGMA. On these bases, plant-growth-promoting potential of bacterium strains with activities of solubilizing phosphorus, solubilizing potassium and producing IAA was also evaluated. Results show that 67 endophytic bacterium strains are obtained from different parts of D. loddigesii collected from different locations, and their distribution characteristics show a specificity of region and tissue. In which, number of endophytic bacterium strains in plants collected from Guangxi is the most (42 strains) and that isolated from stem is the most (34 strains). 67 endophytic bacterium strains are divided into 31 ARDRA clusters, which are identified into 12 genera including Pseudomonas, Microbacterium, Enterobacter, Bacillus, Sphingomonas, Staphylococcus, Psychrobacter, Brevundimonas, Nesterenkonia, Paracoccus, Pantoea and Serratia by ways of 16S rDNA sequence alignment and the dominant genera are Bacillus, Microbacterium and Enterobacter. And abundance and diversity of endophytic bacteria in plants collected from Guangxi are higher than those from other two locations. In 67 endophytic bacterium strains, 30 strains possess double activities of solubilizing inorganic and organic phosphorus, 22 strains do the solubilizing potassium activity and 24 strains do the producing IAA activity, in which, only 8 strains possess all of three plant-growth-promoting activities. Result of tissue culture experiment shows that 1×10⁶ CFU·mL^-1 DLB20 strain of Bacillus is inoculated on the medium, which can promote growth of D. loddigesii plantlets with height of 2-3 cm and3-4 cm, and is beneficial to rooting of plantlets with height of 3-4 cm, meaning that the strains with activities of solubilizing phosphorus, solubilizing potassium and producing IAA possess the plant-growth-promoting potential to D. loddigesii plantlets.