The use of plant growth-promoting microorganisms is an effective agricultural practice to improve plant growth, especially under abiotic stress. In this study, the combined impact of three plant growth-promoting bacteria (PGPB) namely Brevibacterium halotolerans (Sd-6), Burkholderia cepacia (Art-7), Bacillus subtilis (Ldr-2) were tested with Trichoderma harzianum (Th) (possessing ACC deaminase producing activity) in Ocimum basilicum L. cv. “Saumya” to reduce drought-induced damages to the plants under different level of drought stress [i.e. well-watered (100 %), moderate (60 %), severe (40 %)]. These PGPB strains, along with Th, were found to be tolerant against osmotic stress when tested in growth media containing different concentrations of polyethylene glycol (PEG 8000), and all were found to endure -0.99 MPa water potential. Compared to non-inoculated control, Th+Ldr-2 treatment improved fresh herb weight (62.45 %) and oil content (61.54 %) and higher photosynthetic rate under severe drought. Besides, in relation to control, the above treatment enhanced nutrient uptake, reduced ABA, ACC as well as ethylene levels and increased IAA content in addition to an increase in important constituents of essential oil, indicating better performance in terms of plant growth under drought. Higher RWC, decreased MDA, and reduced antioxidant activities in Th+Ldr-2 treated plants compared to non-inoculated control under drought support the mechanism of the microbes providing tolerance against drought. Colony forming unit of microbes and scanning electron microscopy (SEM) study support the effective colonisation behaviour of Th+Ldr-2, which protects plants against drought stress. A consortium of diverse microbes, found to improve plant growth under drought through increased nutrient uptake, reducing the levels of ACC and ABA, improving the content of IAA, antioxidant enzymes probably reducing the effect of drought stress and improving plant biomass could be a useful tool to reduce drought-induced losses in crop plants.

中文翻译：

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产生 ACC 脱氨酶的植物生长促进微生物的协同作用为 Ocimum basilicum L. cv. “Saumya” 提供了耐旱性


使用促进植物生长的微生物是改善植物生长的有效农业实践，尤其是在非生物胁迫下。在这项研究中，测试了三种植物生长促进细菌 （PGPB） 的综合影响，即盐胁迫短杆菌 （Sd-6）、洋葱伯克霍尔德菌 （Art-7）、枯草芽孢杆菌 （Ldr-2） 与哈茨木霉 （Th）（具有 ACC 脱氨酶产生活性）在罗勒木霉 L. cv. “Saumya” 中，以减少干旱对不同干旱胁迫水平下植物的损害 [即浇水充足 （100 %）、 中等 （60 %）、 严重 （40 %）]。在含有不同浓度聚乙二醇 （PEG 8000） 的生长培养基中测试时，发现这些 PGPB 菌株和钍对渗透胁迫具有耐受性，并且发现所有菌株都能承受 -0.99 MPa 的水势。与未接种对照相比，Th+Ldr-2 处理在严重干旱下提高了鲜草重 （62.45 %） 和含油量 （61.54 %），光合速率更高。此外，在控制方面，上述处理除了增加精油的重要成分外，还增强了养分吸收，降低了 ABA、ACC 和乙烯水平，增加了 IAA 含量，表明在干旱下植物生长表现更好。与干旱下未接种的对照相比，Th+Ldr-2 处理的植物中较高的 RWC、降低的 MDA 和降低的抗氧化活性支持微生物提供抗旱性的机制。微生物的菌落形成单位和扫描电子显微镜 （SEM） 研究支持 Th+Ldr-2 的有效定植行为，从而保护植物免受干旱胁迫。 一个由多种微生物组成的联盟，被发现可以通过增加养分吸收、降低 ACC 和 ABA 的水平、提高 IAA 的含量来改善干旱下的植物生长，抗氧化酶可能减少干旱胁迫的影响并改善植物生物量，这可能是减少干旱引起的作物损失的有用工具。