Common root rot, caused by Bipolaris sorokiniana, is one of the most prevalent diseases of wheat and has led to major declines in wheat yield and quality worldwide. Here, strain XZ34-1 was isolated from soil and identified as Bacillus amyloliquefaciens based on the morphological, physiological, biochemical characteristics and 16S rDNA sequence. Culture filtrate (CF) of strain XZ34-1 showed a high inhibition rate against B.sorokiniana and had a broad antifungal spectrum. It also remarkably inhibited the mycelial growth and spore germination of B. sorokiniana. In pot control experiments, the incidence and disease index of common root rot in wheat seedlings were decreased after treatment with CF, and the biological control efficacy was significant, up to 78.24%. Further studies showed XZ34-1 could produce antifungal bioactive substances and had the potential of promoting plant growth. Lipopeptide genes detection with PCR indicated that strain XZ34-1 may produce lipopeptides. Furthermore, activities of defense-related enzymes were enhanced in wheat seedlings after inoculation with B.sorokiniana and treatment with CF, which showed induced resistance could be produced in wheat to resist pathogens. These results reveal that strain XZ34-1 is a promising candidate for application as a biological control agent against B.sorokiniana.
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.
Rhizoctonia cerealis is a worldwide soil-borne pathogenic fungus that significantly infects wheat and causes sharp eyespot in China. However, the biocontrol strains used for the control of Rhizoctonia cerealis are insufficient. In the present study, antagonistic strain B1302 from the rhizosphere of wheat were isolated and identified as Bacillus mojovensis based on their morphological, physiological, and biochemical characteristics, and their 16S rDNA sequence. Culture filtrate of strain B1302 had a broad antifungal spectrum. In order to improve the antifungal activity of B1302, response surface methodology (RSM) was used to optimize the culture conditions. The final medium composition and culture conditions were 13.2 g/L of wheat bran, 14.1 g/L of soybean meal, 224 r/min of rotation speed, 7.50 of initial pH, and 1.5 × 108 CFU/mL of inoculation amount at 35 °C for a culture duration of 72 h. B. mojavensis B1302 inhibited the hyphae growth of R. cerealis and produced hydrolytic enzymes (protease, chitinase, and glucanase), IAA, and had N-fixing potentiality and P-solubilisation capacity. It can also promote wheat seedling growth in potted plants. The disease incidence and index of wheat seedlings were consistent with the effect of commercial pesticides under treatment with culture filtrate. The biocontrol efficacy of culture filtrate was significant—up to 65.25%. An animal toxicological safety analysis suggested that culture filtrate was safe for use and could be developed into an effective microbial fungicide to control wheat sharp eyespot.
IntroductionBipolaris sorokiniana is the popular pathogenic fungi fungus which lead to common root rot and leaf spot on wheat. Generally, chemical fungicides are used to control diseases. However, the environmental pollution resulting from fungicides should not be ignored. It is important to study the mode of antagonistic action between biocontrol microbes and plant pathogens to design efficient biocontrol strategies.ResultsAn antagonistic bacterium DB2 was isolated and identified as Bacillus amyloliquefaciens. The inhibition rate of cell-free culture filtrate (CF, 20%, v/v) of DB2 against B. sorokiniana reached 92.67%. Light microscopy and scanning electron microscopy (SEM) showed that the CF significantly altered the mycelial morphology of B. sorokiniana and disrupted cellular integrity. Fluorescence microscopy showed that culture filtrate destroyed mycelial cell membrane integrity, decreased the mitochondrial transmembrane potential, induced reactive oxygen species (ROS) accumulation, and nuclear damage which caused cell death in B. sorokiniana. Moreover, the strain exhibited considerable production of protease and amylase, and showed a significant siderophore and indole-3-acetic acid (IAA) production. In the detached leaves and potted plants control assay, B. amyloliquefacien DB2 had remarkable inhibition activity against B. sorokiniana and the pot control efficacy was 75.22%. Furthermore, DB2 suspension had a significant promotion for wheat seedlings growth.ConclusionB. amyloliquefaciens DB2 can be taken as a potential biocontrol agent to inhibit B. sorokiniana on wheat and promote wheat growth.
In the overall situation where artificial intelligence services is developing rapidly and the dependency of people on service type mobile software increases day by day and to meet the demands of consumers of pursuing better experience and personalized ideas, this paper takes user experience as the object of study to discuss the user experience in game style navigation APP and analyzes the factors impacting the interface design of navigation APP through the aspects including visual factor, emotion factor and interaction factor, etc and optimizes the interface design of navigation APP through the gamification mode. The paper takes the interface design of "Arbitrary Door" navigation APP as an example to accomplish the import of game style in the interface design of navigation APP and realizes the optimization of interface design of navigation APP based on user experience. This paper also finds that the interface design of navigation APP integrated with game style can adapt to the trend of the times and meet the demands of users through building of user model analysis.
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