Abstract

Beneficial endophytes are key factors in plant productivity and disease control; therefore, research is ongoing to characterize the potential of endophytes as microbial inoculants to promote plant growth and act as biocontrol agents. In this study, we searched for and identified a set of endophytes occurring naturally in a few important crops. Beneficial endophytes were shown to antagonize several important fungi and bacteria, in particular those affecting tomato (Solanum lycopersicum), including Rhizoctonia solani, Alternaria alternata, Clavibacter michiganensis pv. michiganensis, Ralstonia solanacearum, and Xanthomonas vesicatoria. We characterized the most promising as potential inoculants of tomato, aiming to foster plant growth and control the bacterial spot disease caused by Xanthomonas vesicatoria. Among the selected endophytes, we identified a novel streptomycetes, taxonomically related to Streptomyces avermitilis and a pseudomonad, identified as Pseudomonas granadensis. The beneficial effects of these two bacteria, used as single inoculants or as a combination of both, were seen in a significant increase in root and shoot length (approximately 31% and 34% for the streptomycetes and 18% and 16% for the pseudomonad) and dry root biomass (90% for the streptomycetes and 70% for the pseudomonad). Additionally, both inoculants reduced disease progression and severity following inoculation with X. vesicatoria. There was no significant difference between plants treated with single inoculants and plants treated with both. The penetration and efficient colonization of tomato tissues by a green fluorescent protein-tagged culture of the streptomycetes was observed by confocal microscopy, confirming its endophytic nature.

摘要

有益的内生菌是植物生产力和疾病控制的关键因素；因此，正在进行研究以表征内生菌作为微生物接种剂促进植物生长和作为生物防治剂的潜力。在这项研究中，我们搜索并鉴定了一组天然存在于一些重要作物中的内生菌。有益的内生菌被证明可以拮抗几种重要的真菌和细菌，尤其是那些影响番茄 ( Solanum lycopersicum ) 的真菌和细菌，包括立枯丝核菌、交替链格孢菌、密西根棒状杆菌pv。michiganensis、Ralstonia solanacearum和Xanthomonas vesicatoria. 我们将最有前途的番茄定性为潜在的接种剂，旨在促进植物生长并控制由黄单胞菌引起的细菌性斑点病。在选定的内生菌中，我们鉴定了一种新的链霉菌，在分类学上与阿维链霉菌和一种假单胞菌相关，被鉴定为Pseudomonas granadensis. 这两种细菌用作单一接种剂或两者结合使用，其有益效果是显着增加根和枝条长度（链霉菌约 31% 和 34%，假单胞菌约 18% 和 16%）和干根生物量（链霉菌为 90%，假单胞菌为 70%）。此外，两种接种剂在接种X. vesicatoria后都降低了疾病进展和严重程度。用单一接种剂处理的植物和用两种接种剂处理的植物之间没有显着差异。通过共聚焦显微镜观察到链霉菌的绿色荧光蛋白标记培养物对番茄组织的渗透和有效定殖，证实了其内生性。