Minerdi Daniela, Bossi Simone, Gullino Maria Lodovica, Garibaldi Angelo
Centre of Competence for Innovation in Agro-Environmental Field, Agroinnova, University of Torino, via Leonardo da Vinci, 44, 10095 Grugliasco, Italy.
Environ Microbiol. 2009 Apr;11(4):844-54. doi: 10.1111/j.1462-2920.2008.01805.x.
Fusarium oxysporum MSA35 [wild-type (WT) strain] is an antagonistic Fusarium that lives in association with a consortium of bacteria belonging to the genera Serratia, Achromobacter, Bacillus and Stenotrophomonas in an Italian soil suppressive to Fusarium wilt. Typing experiments and virulence tests provided evidence that the F. oxysporum isolate when cured of the bacterial symbionts [the cured (CU) form], is pathogenic, causing wilt symptoms identical to those caused by F. oxysporum f. sp. lactucae. Here, we demonstrate that small volatile organic compounds (VOCs) emitted from the WT strain negatively influence the mycelial growth of different formae speciales of F. oxysporum. Furthermore, these VOCs repress gene expression of two putative virulence genes in F. oxysporum lactucae strain Fuslat10, a fungus against which the WT strain MSA 35 has antagonistic activity. The VOC profile of the WT and CU fungus shows different compositions. Sesquiterpenes, mainly caryophyllene, were present in the headspace only of WT MSA 35. No sesquiterpenes were found in the volatiles of ectosymbiotic Serratia sp. strain DM1 and Achromobacter sp. strain MM1. Bacterial volatiles had no effects on the growth of the different ff. spp. of F. oxysporum examined. Hyphae grownwithVOCfrom WT F. oxysporum f. sp. lactucae strain MSA 35 were hydrophobic whereas those grown without VOCs were not, suggesting a correlation between the presence of volatiles in the atmosphere and the phenotype of the mycelium. This is the first report of VOC production by antagonistic F. oxysporum MSA35 and their effects on pathogenic F. oxysporum. The results obtained in this work led us to propose a new potential direct long-distance mechanism for antagonism by F. oxysporum MSA 35 mediated by VOCs. Antagonism could be the consequence of both reduction of pathogen mycelial growth and inhibition of pathogen virulence gene expression.
尖孢镰刀菌MSA35（野生型菌株）是一种拮抗性镰刀菌，它与一群属于沙雷氏菌属、无色杆菌属、芽孢杆菌属和嗜麦芽窄食单胞菌属的细菌共生，存在于意大利一种对镰刀菌枯萎病具有抑制作用的土壤中。分型实验和毒力测试表明，当尖孢镰刀菌分离株去除细菌共生体（即脱共生体形式）后具有致病性，会引发与尖孢镰刀菌莴苣专化型所导致的相同枯萎症状。在此，我们证明野生型菌株释放的小分子挥发性有机化合物（VOCs）对尖孢镰刀菌不同专化型的菌丝生长具有负面影响。此外，这些VOCs抑制了尖孢镰刀菌莴苣专化型菌株Fuslat10中两个假定毒力基因的表达，野生型菌株MSA 35对该真菌具有拮抗活性。野生型和脱共生体真菌的VOC谱显示出不同的组成。倍半萜类化合物，主要是石竹烯，仅存在于野生型MSA 35的顶空中。在外共生沙雷氏菌属菌株DM1和无色杆菌属菌株MM1的挥发物中未发现倍半萜类化合物。细菌挥发物对所检测的尖孢镰刀菌不同专化型的生长没有影响。用野生型尖孢镰刀菌莴苣专化型菌株MSA 35的VOC培养的菌丝是疏水的，而没有VOCs培养的菌丝则不是，这表明大气中挥发性物质的存在与菌丝表型之间存在相关性。这是关于拮抗性尖孢镰刀菌MSA35产生VOCs及其对致病性尖孢镰刀菌影响的首次报道。这项工作中获得的结果使我们提出了一种由VOCs介导的尖孢镰刀菌MSA 35拮抗作用的新的潜在直接远距离机制。拮抗作用可能是病原菌菌丝生长减少和病原菌毒力基因表达受抑制的共同结果。
