Forest Pathology Laboratory, Biotechnology Center, University of Concepción, Concepción, Chile.
World J Microbiol Biotechnol. 2012 May;28(5):2003-14. doi: 10.1007/s11274-012-1003-8. Epub 2012 Jan 15.
Vegetative propagation by stem cuttings and mini-cuttings has been used worldwide for growing Eucalyptus plants. However, clones and hybrids of this plant present a great variability in their rooting capacity, apart from a gradual decrease in the rooting potential due to the ontogenetic age of the mother plant. Several studies have demonstrated that some bacteria promote plant growth and rooting through the action of direct and indirect mechanisms that are not still completely clear. Considering this, the objective of this study was to assess the production of auxins, abscisic acid and siderophores in Bacillus subtilis and Stenotrophomona maltophilia, which in previous studies increased rooting of E. globulus cuttings. Additionally, the population of these bacteria in the rhizosphere, superficial tissues of the stem-base and callus of the mini-cuttings was identified, and quantified by real-time PCR. Only S. maltophilia produced IAA in the presence of tryptophan; none of the bacterial strains produced ABA, but both produced siderophores. A comparative analysis of the separation profiles showed that there is a diverse microbial community in the rhizosphere, and only S. maltophilia was capable of keeping its population at a density of 2.03 × 10(7) cells/mg in different tissues of the mini-cuttings. The results would indicate that the rooting stimulus in E. globulus could be related to the action of one or several mechanisms such as the production of auxins and siderophores, and it could also be associated with the ability of bacteria to stay in the rhizosphere or in plant callus tissues.
营养繁殖通过茎段扦插和微型扦插已被全世界用于种植桉树植物。然而，该植物的无性系和杂种在生根能力上表现出很大的变异性，此外，由于母株的个体发生年龄，生根潜力逐渐下降。多项研究表明，一些细菌通过直接和间接的作用机制促进植物生长和生根，这些机制尚不完全清楚。考虑到这一点，本研究的目的是评估枯草芽孢杆菌和嗜麦芽寡养单胞菌产生生长素、脱落酸和铁载体的能力，这些细菌在之前的研究中增加了桉树插条的生根。此外，通过实时 PCR 鉴定了这些细菌在根际、茎基部的浅层组织和微型插条愈伤组织中的种群，并对其进行了定量。只有嗜麦芽寡养单胞菌在色氨酸存在的情况下产生 IAA；没有细菌产生 ABA，但都产生铁载体。分离谱的比较分析表明，根际存在着多样化的微生物群落，只有嗜麦芽寡养单胞菌能够在微型插条的不同组织中保持其密度为 2.03×10(7)细胞/mg。结果表明，桉树的生根刺激可能与生长素和铁载体的产生等一种或几种机制有关，也可能与细菌在根际或植物愈伤组织中保持存在的能力有关。
