西瓜复合根际促生菌剂构建与促生效应研究

植物根际促生菌(plant growth-promoting rhizobacteria, PGPR)是微生物肥料的重要菌种资源,在农业生产中起着重要的作用。本实验研究了不同西瓜PGPR分泌激素能力和菌株间的拮抗作用,构建复合菌剂,并研究其对西瓜根系生长的影响。结果表明,12株PGPR均能分泌吲哚乙酸(IAA),Streptomyces CL05分泌量最高达到117.30 mg·L^-1;菌株Sphingomonas CL03、Lysobacter CL02、Microbacterium LS01不产铁载体,菌株Microbacterium LS01、Microbacterium HYL03、Pantoea ananatis HYL01不分泌赤霉素;通过拮抗实验,获得3组复合菌剂,分别为R1、R2和R3。在非灭菌土壤中,与对照相比,复合菌剂R2对西瓜幼苗根长、根表面积、根体积、根尖数和根干质量分别提高了79.0%、46.8%、57.1%、162.7%、49.1%;与对照相比,在灭菌土壤中,复合菌剂R2_S对西瓜幼苗根长、根表面积、根体积、根尖数和根干质量分别提高了191.8%、302.4%、160.0%、206.5%、139.6%,根系平均直径比对照降低了17.5%。复合菌剂R2在灭菌土中的促生效果优于非灭菌土。本研究结果证实,复合菌剂R2对西瓜根系具有明显的促生效应,复合菌剂R2的4株菌分泌赤霉素的能力远远超过R1和R3,这可能是R2促生的机制之一。

Establishment of complex growth-promoting rhizobacteria for watermelon and promoting effect on watermelon roots

Plant growth-promoting rhizobacteria (PGPR) are important species resources of microbial fertilizer, and they play important roles in agriculture production. In this study, the capability of hormone-secreting and antagonistic effect among experimental strains were evaluated, combinations of complex bacteria were constructed, and effect of complex bacteria on watermelon roots were studied. The results showed that the all twelve bacteria strains could secrete indoleacetic acid (IAA), the best one was Streptomyces CL05, whose yield was 117.30 mg·L^-1. Sphingomonas CL03, Lysobacter CL02 and Microbacterium LS01 could not product siderophores, Microbacterium LS01, Microbacterium HYL03 and Pantoea ananatis HYL01 could not secrete gibberellin. Furthermore, three groups of complex bacteria were generated based on the antagonistic experiments, which were named as R1, R2 and R3, respectively. In unsterilized soil, complex bacteria R2 significantly increased root length, root surface area, root volume, root number and root dry weight of watermelon seedlings by 79.0%, 46.8%, 57.1%, 162.7% and 49.1% compared with the control, respectively. In sterilized soil, complex bacteria R2_S increased root length, root surface area, root volume, root number and root dry weight of watermelon seedlings by 191.8%, 302.4%, 160.0%, 206.5% and 139.6% compared with the control, respectively, and decreased root mean diameter of watermelon seedlings by 17.5%. Interestingly, the promoting effect of R2 on watermelon roots was better in sterilized soil than in unsterilized soil. Overall, the study indicated that complex bacteria R2 could significantly promote the growth of watermelon roots, and the ability of gibberellins secretion in R2 (CL03, LS05, HYL02, WZW03) exceeded that in R1 and R3, which may be one of promoting mechanisms of complex bacteria R2.