A potential biocontrol agent Streptomyces tauricus XF for managing wheat stripe rust

Abstract

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a devastating disease threatening global wheat production. Biocontrol by beneficial microorganisms is considered an alternative to synthetic fungicide applications. This study aimed to investigate the mechanisms involved in the biocontrol of wheat stripe rust by streptomycetes. A streptomycete strain XF, isolated from the rhizospheric soil of peony, was identified as Streptomyces tauricus based on morphological characteristics and phylogenetic analysis. We determined the inhibitory effect of XF on Pst and biocontrol effect on the disease using XF fermentation filtrate (FL) and actinomycete cell suspension (AC). Results revealed that FL inhibited urediniospore germination by up to 99% and rendered a lethality rate of 61.47% against urediniospores. Additionally, crude extract of ethyl acetate phase of FL caused cytoplasm releases from urediniospores and the deformation of germ tubes. Furthermore, histochemical analyses revealed that treatments of plants with AC and FL increased reactive oxygen species, inhibited haustorium formation, and reduced the biomass of Pst in leaves. Electron microscopy showed that XF mycelium was able to colonize the leaf surface. Moreover, gene expression assays revealed that AC and FL treatments induced the expression of a number of pathogenesis-related genes in wheat leaves. Besides, in the greenhouse experiments, the control effects of AC and FL reached 65.48% and 68.25%, respectively. In the field, application of XF fermentation broth significantly reduced the disease indices of stripe rust by 53.83%. These findings suggest that XF is a potential biocontrol agent for managing wheat stripe rust disease.