Biocontrol of Wheat Fusarium Head Blight (FHB) by Streptomyces spp. Isolated from the Rhizosphere of Astragalus gombo

Fusarium culmorum is a ubiquitous soil-borne fungus able to cause foot and root rot and Fusarium head blight on different small-grain cereals, in particular wheat and barley. Many rhizospheric actinobacteria isolated from Ononis angustissima Lam. and Astragalus gombo Coss & Dur. were tested for their antagonism against different pathogenic microorganisms in vitro. Among 120 tested isolates, only six isolates (ON03, BI26, BI28, OR6, ON02 and BI15) present a potent antagonistic effect against tested bacterial and fungal pathogens. Cultural and chemical characteristic studies strongly suggested that these strains belong to the genus Streptomyces. All of the six Streptomyces spp. isolates produced relatively high levels of IAA and chitinase. Five Streptomyces spp. strains (BI15, BI26, BI28, ON03 and ON02) solubilize phosphate and four strains (BI15, BI26, ON03 and ON02) produced protease. The in vivo biocontrol assays revealed that the Streptomyces strains significantly promoted the growth of the wheat plants and showed greater suppression of Wheat Fusarium head blight (FHB) disease. All of the six Streptomyces spp. strains showing good effect in increasing seedling emergence of wheat. Our results show that the selected Streptomyces spp. from rhizosphere of Ononis angustissima and Astragalus gombo could be an interesting source for antimicrobial bioactive substances and can efficiently protect wheat against FHB disease.