Nuguse Mimi, Kejela Tekalign
Department of Biology, College of Natural and Computational Sciences, Mattu University, Mettu, Oromia, Ethiopia.
PLoS One. 2024 Aug 1;19(8):e0306837. doi: 10.1371/journal.pone.0306837. eCollection 2024.
Coffee, the second most traded commodity globally after petroleum and is the most exported cash crop of Ethiopia. However, coffee cultivation faces challenges due to fungal diseases, resulting in significant yield losses. The primary fungal diseases affecting coffee production include coffee berry disease, wilt disease (caused by Gibberella xylarioides), and coffee leaf rust. In this study, we aimed to isolate potentially antagonistic actinomycetes from the root rhizosphere of wild Coffea arabica plants in the Yayo coffee forest biosphere in southwestern Ethiopia. Soil samples were collected from the rhizosphere, and actinomycetes were selectively isolated and identified to the genus level by morphological, physiological, and biochemical characterization. These pure isolates were screened for their antagonistic activity against Gibberella xylarioides in vitro using a dual culturing method. Promising isolates demonstrating strong inhibition of fungal mycelial growth were further investigated through in vivo experiments using coffee seedlings. A total of 82 rhizobacteria were isolated. These isolates' inhibition of fungal mycelial growth varied from 0% to 83.3%. Among them, four isolates MUA26, MUA13, MUA52, and MUA14 demonstrated the highest percentage inhibition of fungal mycelial growth: 83.3%, 80%, 76.67%, and 73.3%, respectively. Seedlings inoculated with MUA13, MUA14, and MUA26 during the challenge inoculations (Rhizobacteria + Gibberella xylarioides) exhibited the lowest disease incidence compared to the infected fungi (P < 0.05). Notably, the seedlings inoculated with MUA26 demonstrated the highest disease control efficiency, reaching 83% (P < 0.05). MUA26 was found to produce extracellular enzymes, including chitinase, protease, and lipase, which acted as inhibitors. In summary, this study highlights that MUA26, among the actinomycete isolates, exhibited significant antagonistic activity against Gibberella xylarioides f.sp. coffea. Its efficacy in controlling coffee wilt disease, both in vitro and in vivo, positions it as a potential bioinoculant for managing coffee wilt disease.
咖啡是全球仅次于石油的第二大交易商品，也是埃塞俄比亚出口量最大的经济作物。然而，由于真菌病害，咖啡种植面临挑战，导致产量大幅损失。影响咖啡生产的主要真菌病害包括咖啡浆果病、枯萎病（由木贼赤霉菌引起）和咖啡叶锈病。在本研究中，我们旨在从埃塞俄比亚西南部亚约咖啡森林生物圈的野生阿拉伯咖啡植物根际中分离出具有潜在拮抗作用的放线菌。从根际采集土壤样本，通过形态学、生理学和生化特征对放线菌进行选择性分离并鉴定到属水平。使用双培养法在体外筛选这些纯分离株对木贼赤霉菌的拮抗活性。通过使用咖啡幼苗的体内实验，对显示出对真菌菌丝体生长有强烈抑制作用的有前景的分离株进行进一步研究。共分离出82株根际细菌。这些分离株对真菌菌丝体生长的抑制率在0%至83.3%之间。其中，四个分离株MUA26、MUA13、MUA52和MUA14对真菌菌丝体生长的抑制率最高，分别为83.3%、80%、76.67%和73.3%。在挑战接种（根际细菌+木贼赤霉菌）期间接种MUA13、MUA14和MUA26的幼苗与感染真菌的幼苗相比，发病率最低（P<0.05）。值得注意的是，接种MUA26的幼苗表现出最高的病害防治效率，达到83%（P<0.05）。发现MUA26产生包括几丁质酶、蛋白酶和脂肪酶在内的细胞外酶，这些酶起到抑制剂的作用。总之，本研究强调，在放线菌分离株中，MUA26对咖啡木贼赤霉菌表现出显著的拮抗活性。其在体外和体内控制咖啡枯萎病的功效使其成为管理咖啡枯萎病的潜在生物接种剂。
