烟草根际促生菌(PGPR)的筛选、鉴定及促生机理研究

Screening, identification and plant growth-promotion mechanism of tobacco plants rhizobacteria

筛选并鉴定了贵州烟区烟草根际促生菌(PGPR)菌株。测定PGPR产激素能力、定殖能力以及对烟草苗期促生作用,以具备多项促生能力为筛选标准,确定目标PGPR,再通过16S r DNA、平板对峙以及PCR技术对目标PGPR进行属鉴定、抗病能力测定。通过筛选获得的7株目标PGPR均能产生脱落酸、细胞分裂素、赤霉素和生长素。烟苗盆栽试验表明7株PGPR均具有促生效果,其中LX-7处理的烟苗鲜重和根系活力最大;大田移栽30d后,LX-7根际定殖数量可维持10~7cfu/g根,显著高于其它菌株;抑菌试验证实LX-4、LX-5和LX-7具有广谱抗菌作用。综合考量,LX-4、LX-5和LX-7具有显著的促生效果,经16S rDNA鉴定分别为枯草芽孢杆菌、地衣芽孢杆菌和解淀粉芽孢杆菌。

Plant growth-promoting rhizobacteria was screened and identified in order to build a foundation for tobacco PGPR-bioorganic fertilizer development. Plant growth-promoting rhizobacteria in rhizosphere soils were pre-isolated by considering ammonia, HCN, and siderophores production, phosphate-solubilizing and potassium dissolving capacity. Phytohormone production, colonization and plant- growth-promotion in seedling period were explored to screen PGPR. Target PGPR were identified by 16S rDNA sequencing. Disease- resistance capacity and plant growth-promoting were evaluated. Twenty strains primarily selected had potential plant-growth-promotion ability. All seven re-screened PGPR strains produced abscisic acid, phytokinin, gibberellin and auxin. The population of LX-7 strain in rhizosphere soil was significantly higher than other selected strains and kept 107cfu/g soil 30 days after transplanting. The counts of LX-4 and LX-5 strains were 106cfu/g while the populations of other selected strains significantly decreased. Tobacco seedling experiment showed that seven PGPR had the ability of plant-growth-promotion. Fresh weight and root system activity of LX7 treatment were the highest among all treatments. Chlorophyll content of tobacco seedling in LX5 treatment was significantly higher than that of other treatments. Compared with control, average root length, root diameter, root area and root volume in LX4, LX5 and LX7 treatments increased by 29.21%, 8.49%, 60.3% and 96.94%. LX4, LX5 and LX7 were identified as Bacillus subtilis, Bacillus licheniformis and Bacillus amyloliquefaciens, respectively. These three PGPR had broad spectrum antibiotics. Three PGPR strains, LX4, LX5 and LX7, had remarkable effect on plant-growth-promotion and can be employed as key bacteria in tobacco growth-promotion.