Abstract
Rhizoctonia cerealis is a major fungal pathogen of wheat that causes great yield losses in all wheat-growing regions of the world. The biocontrol agent Bacillus subtilis XZ18-3 was investigated for inhibiting R. cerealis growth in wheat. The results of the mycelial growth test showed that the sterile filtrate of B. subtilis XZ18-3 could significantly inhibit the mycelial growth of R. cerealis and cause swelling and rupture of the mycelium. Observation by transmission electron microscopy indicated that the sterile filtrate could penetrate the cellular membrane of Rhizoctoniacerealis, resulting in organelle destruction. The effect of the sterile filtrates on the pathogen cells, shown through fluorescent microscopy using different stains, revealed the mechanism by which the sterile filtrate caused DNA fragmentation, accumulation of ROS and changes in cell membrane permeability. To reach a better treatment of the soil-borne fungi, the components of a wettable powder were screened and an optimised formula determined (30.0% kaolin, 4.0% polyvinyl alcohol, 8.0% Tween-80, 2.0% polyethylene glycol and 100% fermentation broth). A quality index analysis revealed that the wetting powder reached acceptable biological pesticide standards. Pot control experiments showed that the wettable powder of B. subtilis XZ18-3 effectively controlled the pathogens with an efficacy of 88.28%. This study has provided the potential biocontrol agents (BCAs) for wheat sharp eyespot disease.
Highlights
Wheat (Triticum aestivum L.) is an important crop in the world and diseases caused by soil-borne pathogens threaten its cultivation [1]
In an attempt to develop biological control agents (BCAs) for wheat sharp eyespot disease using antagonistic microorganisms, and to further investigate their actions against the pathogenic fungus R. cerealis, we focused on the mechanism whereby they affected the fungus to improve the biocontrol performance of BCAs
Our results showed by optical microscopy that sterile filtrates of Bacillus subtilis XZ18-3 caused increased mycelia swelling and branching
Summary
Wheat (Triticum aestivum L.) is an important crop in the world and diseases caused by soil-borne pathogens threaten its cultivation [1]. Wheat sharp eyespot is the main disease affecting wheat cultivation, and is caused by the fungus Rhizoctonia cerealis. It can destroy the transport organization of plants, causing nutrients to be unable to transported to various tissues and cells [3]. The popularization of high planting density, and high inputs of irrigation and fertilization have accelerated the spread and severity of R. cerealis [4]. This pathogen is the most severe biotic stress affecting wheat grain yield in some regions of the world, which seriously reduces crop yield [5]
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