Induction of multiple defense responses in wheat plants against stripe rust using mycorrhizal fungi and Streptomyces viridosporus HH1

Abstract

Stripe rust, caused by Puccinia striiformis f. sp. tritici, is one of the most devastating diseases of wheat worldwide. This study dealt with investigating the biocontrol activity of mycorrhizal colonization and/or application of Streptomyces viridosporus HH1 against stripe rust of wheat. In vitro, data showed that S. viridosporus HH1 had a strong anti-spore germination effect on uredospores of P. striiformis (90% reduction). A 84.2% reduction in the disease severity was achieved in the infected wheat plants, which were colonized with mycorrhizal fungi and were sprayed with S. viridosporus HH1. Molecular investigation revealed that mycorrhizal colonization and application of S. viridosporus HH1 upregulated the defensive genes ethylene response factor protein 3 (JERF3) by 20.7-fold, chitinase II (13.6-fold), and β-1,3-glucanase (9.8-fold). Furthermore, mycorrhizal colonization and application of S. viridosporus HH1 led to a significant increase in the activity of the antioxidant enzymes peroxidase (52.3%), polyphenol oxidase (106.9%), and catalase (87.9%). The phenolic content also increased due to mycorrhizal colonization and application of S. viridosporus HH1, while the lipid peroxidation decreased in the infected wheat leaves. A mitigation in the adverse effects of infection on the photosynthetic pigments in wheat leaves was noticed. Observations from transmission electron microscopy showed that different hypersensitivity reactions were induced on the ultrastructural level in the infected wheat cells due to this treatment. In addition, a significant growth-promoting effect was also reported. It can be concluded that mycorrhizal colonization and spraying with S. viridosporus HH1 have a promising biocontrol activity against stripe rust in wheat. Field evaluation is necessary in the future studies before the use recommendation.