Biological control of anthracnose (Colletotrichum gloeosporioides) and high-quality walnut production in walnut (Juglans regia L.) trees by Bacillus licheniformis PR2

IF 3.4 2区 农林科学 Q2 BIOTECHNOLOGY & APPLIED MICROBIOLOGY
Jae-Hyun Moon, Sang-Jae Won, Vantha Choub, Su-In Choi, Ju-Yeol Yun, Henry B. Ajuna, Young Sang Ahn
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引用次数: 0

Abstract

Walnut (Juglans regia L., Fam.: Juglandaceae) is an economically important crop worldwide, but its production is hampered by notorious diseases such as walnut anthracnose caused by Colletotrichum gloeosporioides. This study aims to demonstrate the potential of Bacillus licheniformis PR2 as an alternative to chemical fungicides through the production of bioactive enzymes which degrade the phytopathogenic fungal cell walls to inhibit its mycelial growth and spore germination and consequently suppress anthracnose disease. The study further demonstrates the potential of PR2 to improve the yield and quality of walnut kernels through phytohormone production and improving nutrient availability in soil. During its growth in the bacterial culture, PR2 exhibited strong antifungal potential by producing cell wall degrading enzymes such as chitinase, β-1,3-glucanase and protease which degraded the cell wall chitin, β-glucans and glycoproteins polymers of C. gloeosporioides. The crude enzyme fraction of PR2 at 100 µL/mL inhibited spore germination and mycelial growth of C. gloeosporioides by 89.22 % and 33.31 %, respectively. Field application of PR2 culture resulted in 3.60-fold and 3.47-fold reduction of anthracnose disease incidence compared to the conventional treatment and control groups, respectively. For the growth-promoting properties, PR2 produced indole-3-acetic acid (IAA), a phytohormone known to enhance root development up to 148.49 mg/mL during growth and demonstrated the potential for phosphate-solubilization and ammonium-nitrogen production, thereby increasing the availability of essential nutrients in the soil. Application of PR2 in the field elevated the concentration of nitrogen and available phosphorus by 1.70-fold and by 1.56-fold compared to the conventional treatment and control group, respectively. Inoculation of PR2 also elevated the concentration of available phosphate in the rhizosphere by 2.57-fold and 2.67-fold compared to the conventional treatment and control group, respectively. These growth-promoting properties improved the uptake of essential nutrients by walnut plants and resulted in higher chlorophyll content/photosynthetic capacity in walnut leaves, which in turn resulted in higher yield and improved physical characteristics of walnut kernels, such as the average kernel length, diameter, weight and firmness. Moreover, the inoculation of PR2 in walnut field increased calcium uptake and content in walnut kernel by promoting calcium solubilization from metal complexes through organic acid production (lowering soil pH) and the increased Ca content improved kernel firmness by reinforcing the pellicle cell walls. These findings demonstrate that B. licheniformis PR2 has dual potential to directly inhibit phytopathogenic infections through enzymatic degradation of the fungal cell walls while simultaneously inducing beneficial physiological processes to improve walnut yield and kernel quality. Therefore, B. licheniformis PR2 could potentially be applied as an eco-friendly alternative to chemical fungicides and fertilizers for sustainable disease control and improving the production of high-quality walnut kernels.
地衣芽孢杆菌PR2对核桃炭疽病的生物防治及优质核桃产量的影响
核桃(Juglans regia L., Fam)核桃炭疽病(炭疽病)是世界范围内重要的经济作物,但其生产受到炭疽菌引起的核桃炭疽病等臭名昭著的疾病的阻碍。本研究旨在证明地衣芽孢杆菌PR2作为化学杀菌剂的替代品的潜力,通过生产生物活性酶来降解植物病原真菌细胞壁,抑制其菌丝生长和孢子萌发,从而抑制炭疽病。该研究进一步证明了PR2通过产生植物激素和改善土壤养分有效性来提高核桃仁产量和品质的潜力。PR2在细菌培养过程中产生几丁质酶、β-1,3-葡聚糖酶和蛋白酶等细胞壁降解酶,可降解黄孢霉细胞壁几丁质、β-葡聚糖和糖蛋白聚合物,表现出较强的抗真菌潜能。100µL/mL时,PR2粗酶组分对gloeosporioides孢子萌发和菌丝生长的抑制作用分别为89.22%和33.31%。田间应用PR2培养后,与常规处理组和对照组相比,炭疽病发病率分别降低3.60倍和3.47倍。在促进生长方面,PR2产生吲哚-3-乙酸(IAA),这是一种植物激素,已知在生长过程中促进根系发育,最高可达148.49 mg/mL,并显示出磷酸盐增溶和氨氮生产的潜力,从而增加土壤中必需养分的有效性。田间施用PR2使氮素和有效磷浓度分别比常规处理和对照组提高1.70倍和1.56倍。接种PR2可使根际有效磷浓度分别比常规处理和对照组提高2.57倍和2.67倍。这些促进生长的特性提高了核桃植株对必需营养物质的吸收,提高了核桃叶片叶绿素含量和光合能力,从而提高了产量,改善了核桃仁的平均粒长、直径、重量和硬度等物理特性。此外,在核桃田间接种PR2通过产生有机酸(降低土壤pH)促进金属配合物对钙的增溶作用,增加了核桃仁对钙的吸收和含量,增加了钙含量,增强了核桃仁的外膜细胞壁,提高了核桃仁的硬度。这些发现表明,地衣芽胞杆菌PR2具有双重潜力,通过酶降解真菌细胞壁直接抑制植物病原感染,同时诱导有益的生理过程提高核桃产量和籽粒品质。因此,地衣芽孢杆菌PR2有可能作为化学杀菌剂和肥料的环保替代品,用于可持续的疾病控制和提高优质核桃仁的产量。
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来源期刊
Biological Control
Biological Control 生物-昆虫学
CiteScore
7.40
自引率
7.10%
发文量
220
审稿时长
63 days
期刊介绍: Biological control is an environmentally sound and effective means of reducing or mitigating pests and pest effects through the use of natural enemies. The aim of Biological Control is to promote this science and technology through publication of original research articles and reviews of research and theory. The journal devotes a section to reports on biotechnologies dealing with the elucidation and use of genes or gene products for the enhancement of biological control agents. The journal encompasses biological control of viral, microbial, nematode, insect, mite, weed, and vertebrate pests in agriculture, aquatic, forest, natural resource, stored product, and urban environments. Biological control of arthropod pests of human and domestic animals is also included. Ecological, molecular, and biotechnological approaches to the understanding of biological control are welcome.
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