Streptomyces strains inhibit the growth of Fusarium kuroshium and Fusarium solani and promote the growth of Arabidopsis thaliana

Abstract

ABSTRACT Three Streptomyces strains (S. lactacystinicus CIAD-IA7, S. cellostaticus CIAD-IA32 and S. lunaelactis CIAD-IA104) were selected among 21 strains of this genus according to their antifungal activity against Fusarium solani (model fungus) and then, used to evaluate their activity against Fusarium kuroshium cultures (target fungus). The in vitro plant growth promoting properties (PGP) of these strains were also determined in A. thaliana seedlings. The three strains suppressed 95.4-97.9% the mycelial growth of F. solani in dual cultures. The exposure of the pathogen to VOCs produced axenically by the Streptomyces strains reduced its growth by 84.3–92.5%, confirming the antifungal properties of VOCs from Streptomyces. The analysis of the head space from axenic cultures of the selected Streptomyces strains revealed the groups of VOCs, but ethylbenzene, o-xylene, 2-pentylfuran, cyclohexene, and 1-methyl-4-(1-methylethenyl)-, (S)- were the most abundant. Further studies with seven pure VOCs that had been identified in selected Streptomyces strains confirmed the antifungal activity of VOCs from Streptomyces against F. solani, with trans-2-hexenal and eucalyptol inhibiting >50 and 100%, respectively, the growth of the pathogen. The inhibition of F. kuroshium by the selected Streptomyces ranged from 51.2 to 64.5% in dual-cultures and from 58.4 to 66.5% by VOCs. Streptomyces strains also produced indole-3-acetic acid and siderophores. VOCs from Streptomyces cultures also favoured biomass accumulation in A. thaliana seedlings. The most significant increases in biomass were observed in root length, plant fresh weight, and root fresh weight. The selected Streptomyces strains might be candidates to be used as biofungicides and biofertilisers.