Abstract
Fusarium wilt of cotton, caused by the pathogenic fungal Fusarium oxysporum f. sp. vasinfectum (Fov), is a devastating disease of cotton, dramatically affecting cotton production and quality. With the increase of pathogen resistance, controlling Fusarium wilt disease has become a significant challenge. Biocontrol agents (BCAs) can be used as an additional solution to traditional crop breeding and chemical control. In this study, an actinomycete with high inhibitory activity against Fov was isolated from rhizosphere soil and identified as Streptomyces alfalfae based on phylogenetic analyses. Next, an integrative approach combining genome mining and metabolites detection was applied to decipher the significant biocontrol and plant growth-promoting properties of XN-04. Bioinformatic analysis and bioassays revealed that the antagonistic activity of XN-04 against Fov was associated with the production of various extracellular hydrolytic enzymes and diffusible antifungal metabolites. Genome analysis revealed that XN-04 harbors 34 secondary metabolite biosynthesis gene clusters. The ability of XN-04 to promote plant growth was correlated with an extensive set of genes involved in indoleacetic acid biosynthesis, 1-aminocyclopropane-1-carboxylic acid deaminase activity, phosphate solubilization, and iron metabolism. Colonization experiments indicated that EGFP-labeled XN-04 had accumulated on the maturation zones of cotton roots. These results suggest that S. alfalfae XN-04 could be a multifunctional BCA and biofertilizer used in agriculture.
Highlights
Fusarium wilt of cotton, caused by the pathogen Fusarium oxysporum f. sp. vasinfectum (Fov) W.C
To further analyze the number of active antifungal metabolites in the EtOAc extract, Thin layer chromatography (TLC) chromatogram strips were placed on the surface of Potato Dextrose Agar (PDA) plates containing Fov spores
A total of 32 morphologically different actinomycetes were isolated from the rhizosphere soil collected in Gansu and Qinghai Provinces, China
Summary
Fusarium wilt of cotton, caused by the pathogen Fusarium oxysporum f. sp. vasinfectum (Fov) W.C. The systematic investigation of Streptomyces species at the genetic level is becoming more important for counteracting pathogens Their filaments and ability to sporulate help them cleave strongly to the rhizospheric soil particles forming a strong bond with the plants (Olanrewaju and Babalola, 2019). We obtain a potential BCA, S. alfalfae XN-04, which displayed plant growth-promoting activity and a strong antagonistic activity against Fov. To better understand the mechanisms underlying the diverse and beneficial biological activities of this strain, we assessed the following objectives: (1) evaluate the biocontrol efficacy of XN-04 under greenhouse conditions, (2) evaluate the effect of XN-04 on cotton growth, (3) a comprehensive genome sequence analysis of XN-04, (4) characterize the metabolites produced by XN-04, and (5) evaluate the colonization ability of XN-04 in cotton roots, and all these information provided essential insights into the biocontrol properties of S. alfalfae XN-04
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