Abdelkhalek Ahmed, El-Gendi Hamada, Al-Askar Abdulaziz A, Maresca Viviana, Moawad Hassan, Elsharkawy Mohsen M, Younes Hosny A, Behiry Said I
Department of Plant Protection and Biomolecular Diagnosis, Arid Lands Cultivation Research Institute (ALCRI), City of Scientific Research and Technological Applications, Alexandria, Egypt.
Department of Bioprocess Development, Genetic Engineering and Biotechnology Research Institute, City of Scientific Research and Technological Applications, Alexandria, Egypt.
Front Plant Sci. 2022 Aug 2;13:933498. doi: 10.3389/fpls.2022.933498. eCollection 2022.
spp. manifests strong nitrogen fixation ability in legumes. However, their significance as biocontrol agents and antivirals has rarely been investigated. Under greenhouse conditions, the molecularly identified nitrogen-fixing plant growth-promoting rhizobacteria (PGPR), bv. strain 33504-Alex1, isolated from the root nodules of faba bean plants, was tested as a soil inoculum or a foliar application to trigger faba bean plants' resistance against (BYMV) infection. Compared to the non-treated faba bean plants, the applications of 33504-Alex1 in either soil or foliar application significantly promoted growth and improved total chlorophyll content, resulting in a considerable reduction in disease incidence and severity and the inhibition index of BYMV in the treated faba bean plants. Furthermore, the protective activities of 33504-Alex1 were associated with significant reductions in non-enzymatic oxidative stress markers [hydrogen peroxide (HO) and malondialdehyde (MDA)] and remarkably increased DPPH free radical scavenging activity and total phenolic content compared to the BYMV treatment at 20 days post-inoculation. Additionally, an increase in reactive oxygen species scavenging enzymes [superoxide dismutase (SOD) and polyphenol oxidase (PPO)] and induced transcriptional levels of pathogenesis-related (PR) proteins (, , and ) were observed. Of the 19 polyphenolic compounds detected in faba bean leaves by high-performance liquid chromatography (HPLC) analysis, gallic and vanillic acids were completely shut down in BYMV treatment. Interestingly, the 33504-Alex1 treatments were associated with the induction and accumulation of the most detected polyphenolic compounds. Gas chromatography-mass spectrometry (GC-MS) analysis showed hexadecanoic acid 2,3-dihydroxypropyl ester, tetraneurin-A-Diol, oleic acid, and isochiapin B are the major compounds in the ethyl acetate extract of 33504-Alex1 culture filtrate (CF), suggesting it acts as an elicitor for the induction of systemic acquired resistance (SAR) in faba bean plants. Consequently, the capacity of bv. strain 33504-Alex1 to enhance plant growth and induce systemic resistance to BYMV infection will support the incorporation of 33504-Alex1 as a fertilizer and biocontrol agent and offer a new strategy for crop protection, sustainability, and environmental safety in agriculture production.
某些物种在豆科植物中表现出很强的固氮能力。然而，它们作为生物防治剂和抗病毒剂的重要性却很少被研究。在温室条件下，从蚕豆植物根瘤中分离出的经分子鉴定的固氮促植物生长根际细菌（PGPR），即bv. 菌株33504-Alex1，作为土壤接种物或叶面喷施剂进行测试，以激发蚕豆植物对蚕豆黄花叶病毒（BYMV）感染的抗性。与未处理的蚕豆植物相比，33504-Alex1无论是作为土壤接种物还是叶面喷施剂，都显著促进了生长并提高了总叶绿素含量，导致处理后的蚕豆植物中BYMV的发病率、病情严重程度和抑制指数大幅降低。此外，与接种BYMV后20天的处理相比，33504-Alex1的保护活性与非酶促氧化应激标志物[过氧化氢（HO）和丙二醛（MDA）]的显著降低以及DPPH自由基清除活性和总酚含量的显著增加有关。此外，还观察到活性氧清除酶[超氧化物歧化酶（SOD）和多酚氧化酶（PPO）]增加以及病程相关（PR）蛋白（、和）的转录水平诱导。通过高效液相色谱（HPLC）分析在蚕豆叶片中检测到的19种多酚化合物中，没食子酸和香草酸在BYMV处理中完全被抑制。有趣的是，33504-Alex1处理与大多数检测到的多酚化合物的诱导和积累有关。气相色谱-质谱（GC-MS）分析表明，十六烷酸2,3-二羟丙酯、四氢神经酰胺-A-二醇、油酸和异鹰爪豆碱B是33504-Alex1培养滤液（CF）乙酸乙酯提取物中的主要化合物，表明它作为一种激发子诱导蚕豆植物产生系统获得性抗性（SAR）。因此，bv. 菌株33504-Alex1增强植物生长并诱导对BYMV感染的系统抗性的能力将支持将33504-Alex1用作肥料和生物防治剂，并为农业生产中的作物保护、可持续性和环境安全提供一种新策略。
