Abstract Palm oil has high economic value in Southeast Asia as a primary source of vegetable oil and in biofuel production. The plant is frequently damaged from the fungal infection of Ganoderma boninense, causing basal stem rot (BSR) disease. This pathological problem results in significant yield loss and death of oil palm trees. The present study aims to develop actinomycetes as inoculants and to evaluate their ability to control this disease. Streptomyces noursei CMU-AB21, Streptomyces sioyaensis CMU-AB83, and Streptomyces palmae CMU-AB204T exhibited the strongest degree of anti-Ganoderma activity in vitro and were chosen as potential biocontrol agents. The actinomycetes were encapsulated in 2% (w/v) sodium alginate at an initial concentration of 109 cfu mL−1. The efficiency of these actinomycetes on the in vivo suppression of BSR was evaluated in oil palm seedlings using spore immobilized alginate beads and free-spore suspension. The most effective inoculant, S. palmae CMU-AB204T, revealed the lowest severity of foliar symptoms (SFS) at 3.7% and 4.5%, and reduced the percentage of disease severity by 81.6% and 75.8% when applied as free-spores and spores encapsulating alginate beads, respectively. Moreover, the seedlings treated with S. palmae CMU-AB204T had the highest degree of plant vigor based on stem diameter and biomass. The bioactive metabolites of this strain were isolated from broth extracts by column chromatography. Mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectra indicated that the compounds produced by S. palmae CMU-AB204T were actinopyrone A (1), anguinomycin A (2) and leptomycin A (3), which revealed inhibitory activity towards G. boninense at 50, 5 and 1.5 µg disk−1, respectively. Based on this evidence, S. palmae CMU-AB204T is a promising candidate in the development of a biocontrol agent that would protect oil palm trees from BSR disease.

中文翻译：

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Streptomyces palmae CMU-AB204T，一种抗真菌放线菌，作为一种潜在的生物防治剂，可以保护棕榈油生产树木免受基部茎腐病真菌 Ganoderma boninense 的侵害

摘要 棕榈油作为植物油和生物燃料生产的主要来源，在东南亚具有很高的经济价值。该植物经常因灵芝真菌感染而受损，导致基部茎腐病 (BSR) 病。这种病理问题导致油棕树的显着产量损失和死亡。本研究旨在开发作为接种剂的放线菌并评估它们控制这种疾病的能力。Streptomyces noursei CMU-AB21、Streptomyces sioyaensis CMU-AB83 和 Streptomyces palmae CMU-AB204T 在体外表现出最强的抗灵芝活性，被选为潜在的生物防治剂。将放线菌封装在 2% (w/v) 海藻酸钠中，初始浓度为 109 cfu mL-1。使用固定孢子的藻酸盐珠和游离孢子悬浮液在油棕幼苗中评估了这些放线菌对 BSR 体内抑制的效率。最有效的接种剂 S. palmae CMU-AB204T 显示叶状症状 (SFS) 的严重程度最低，分别为 3.7% 和 4.5%，当以游离孢子和孢子施用时，疾病严重程度的百分比分别降低了 81.6% 和 75.8%分别封装海藻酸盐珠。此外，根据茎直径和生物量，用棕榈树 CMU-AB204T 处理的幼苗具有最高程度的植物活力。通过柱层析从肉汤提取物中分离出该菌株的生物活性代谢物。质谱 (MS) 和核磁共振 (NMR) 谱表明，棕榈树 CMU-AB204T 产生的化合物为放线菌酮 A (1)，Anguinomycin A (2) 和 Leptomycin A (3)，分别在 50、5 和 1.5 µg disk-1 时显示出对 G. boninense 的抑制活性。基于这一证据，棕榈油树 CMU-AB204T 是开发可保护油棕树免受 BSR 病害的生物防治剂的有希望的候选者。