Guevara-Avendaño Edgar, Carrillo Joseph D, Ndinga-Muniania Cedric, Moreno Kevin, Méndez-Bravo Alfonso, Guerrero-Analco José A, Eskalen Akif, Reverchon Frédérique
Red de Estudios Moleculares Avanzados, Instituto de Ecología A.C., Carretera antigua a Coatepec 351, 91070, Xalapa, Veracruz, Mexico.
Department of Plant Pathology and Microbiology, University of California - Riverside, Riverside, 92521, CA, USA.
Antonie Van Leeuwenhoek. 2018 Apr;111(4):563-572. doi: 10.1007/s10482-017-0977-5. Epub 2017 Nov 9.
Plant rhizobacteria have been successfully used as biocontrol agents against fungal phytopathogens. However, their potential to control two important avocado diseases, namely Fusarium dieback (FD) and Phytophthora root rot (PRR), has been poorly studied. FD is an emerging disease triggered by fungi associated with two ambrosia beetle species (Euwallacea fornicatus species complex), while PRR is caused by Phytophthora cinnamomi, a soil-borne oomycete. In the present work, the antifungal activity of bacteria isolated from avocado rhizosphere was tested in dual culture assays against Fusarium euwallaceae, Graphium euwallaceae and Graphium sp., causal agents of FD, and against P. cinnamomi. In 2015, rhizosphere soil samples of FD infested and non-infested avocado trees were collected from a commercial avocado orchard in Escondido, California. In an initial screening, 72 of the 168 assessed bacterial isolates reduced mycelial growth of F. euwallaceae by up to 46%. Eight bacterial isolates showing inhibition percentages larger than 40% were then selected for further antagonism assays against the other fungal pathogens. Five bacterial isolates, determined by 16S rDNA sequencing to belong to the Bacillus subtilis/Bacillus amyloliquefaciens species complex, successfully inhibited the mycelial growth of both Graphium species by up to 30%. The same isolates and an additional isolate identified as Bacillus mycoides, inhibited the growth of P. cinnamomi by up to 25%. This is the first report of avocado rhizobacteria with antifungal activity against pathogens responsible for FD and PRR in avocado.
植物根际细菌已成功用作对抗真菌植物病原体的生物防治剂。然而，它们控制两种重要鳄梨病害的潜力，即镰刀菌枯萎病（FD）和樟疫霉根腐病（PRR），尚未得到充分研究。FD是一种由与两种食菌小蠹虫（Euwallacea fornicatus物种复合体）相关的真菌引发的新出现病害，而PRR是由土壤传播的卵菌樟疫霉引起的。在本研究中，在双培养试验中测试了从鳄梨根际分离的细菌对FD的致病因子枯萎病菌、可可毛色二孢和毛色二孢属，以及对樟疫霉的抗真菌活性。2015年，从加利福尼亚州埃斯孔迪多的一个商业鳄梨园采集了受FD侵染和未受侵染的鳄梨树的根际土壤样本。在初步筛选中，168株评估的细菌分离物中有72株使枯萎病菌的菌丝生长减少了46%。然后选择8株抑制率大于40%的细菌分离物，对其他真菌病原体进行进一步的拮抗试验。通过16S rDNA测序确定属于枯草芽孢杆菌/解淀粉芽孢杆菌物种复合体的5株细菌分离物，成功地使两种毛色二孢属真菌的菌丝生长抑制率高达30%。相同的分离物和另外一株鉴定为蕈状芽孢杆菌的分离物，使樟疫霉的生长抑制率高达25%。这是关于鳄梨根际细菌对鳄梨中导致FD和PRR的病原体具有抗真菌活性的首次报道。
