Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2019 Aug 12;14(8):e0220410.
doi: 10.1371/journal.pone.0220410. eCollection 2019.

The isolation of the antagonistic strain Bacillus australimaris CQ07 and the exploration of the pathogenic inhibition mechanism of Magnaporthe oryzae

Wenqian Chen  1 , Lu Zhao  1 , Hui Li  1 , Yilun Dong  1 , Hong Xu  1 , Ying Guan  1 , Songhao Rong  1 , Xiaoling Gao  1 , Rongjun Chen  1 , Lihua Li  1 , Zhengjun Xu  1
Affiliations

The isolation of the antagonistic strain Bacillus australimaris CQ07 and the exploration of the pathogenic inhibition mechanism of Magnaporthe oryzae

Wenqian Chen et al. PLoS One. .

Abstract

Biological control as a promising method to combat plant disease has gained public attention in recent years. In the present study, we isolated 12 strains resistant to Magnaporthe oryzae from western Sichuan subalpine soil. Among them, CQ07 exhibited remarkable activity against M. oryzae. The result of 16S rRNA sequence analysis revealed that CQ07 is approximately 99% similar to Bacillus australimaris. The sterilized culture filtrate of CQ07 inhibited the growth of M. oryzae, which motivated us to deduce the influence of CQ07 on the pathogenicity of M. oryzae. As shown by experimentation, sterilized culture filtrate (10 μl/ml) of CQ07 can delay and even suppress the germination of conidia and prevent the formation of appressorium in vitro and in vivo. In addition, by simulative field tests, the spraying of conidia suspension diluted with sterilized culture filtrate of CQ07 reduced infection of rice blast. To better control rice blasts, understanding the infection mechanism of M. oryzae and inhibiting the mechanism of the antagonistic strain is of great importance.

PubMed Disclaimer

Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. CQ07 showed a strong inhibitory effect against M. oryzae Guy11.
CQ02, CQ03, CQ04, CQ05, CQ07, and CQ09 all showed inhibition against M. oryzae GUY11, but CQ07 had the strongest inhibition effect.
Fig 2
Fig 2. Neighbor-joining phylogenetic tree of CQ07 based on 16S rRNA sequence analysis.
Fig 3
Fig 3. Morphological characteristics of CQ07.
A. Colony morphology of CQ07. B. Gram staining of CQ07. C. Spore staining of CQ07. D. Capsule staining of CQ07.
Fig 4
Fig 4. Germination rate of conidia at different times.
The control group had already germinated after 2 hours, while the treatment group had not yet germinated. At 4 hours, the treatment group began to germinate, but the rate of germinated conidia was only 27%. After 8 hours, the germination rate of the treatment group was almost always stable at 83%, while the germination rate of the control group was 97%.
Fig 5
Fig 5
A. Germination of conidia at different time points in the control group. B. Germination of conidia at different time points in the treatment group. At 4 hours, 85% of appressorium of the control group was formed. After 8 hours, endlessly extended and unusual mycelium growth were observed in the treatment group. After 24 hours, the appressorium of the treatment group still did not form. However, after 48 hours, 7% of appressorium was observed in the treatment group. After 60 hours, the appressorium formation rate of the treatment group reached only 10%, while that of the control group reached 85%.
Fig 6
Fig 6. The cell membrane of the treatment group was destroyed by the culture filtrate of CQ07.
Through the FDA-PI staining test, the mycelium of the control group showed the most green fluorescence. The mycelia of the treatment group all showed red fluorescence.
Fig 7
Fig 7. Infection status of conidia at different times.
At 12 hours, appressorium of the control group was observed. At 24 hours, infection pegs of the control group were observed. At 36 hours, the mycelium of the control group infected the neighboring cells. At 24 and 36 hours, the treatment group only extended the malformed mycelium on the surface of the onion cells.
Fig 8
Fig 8. Pathogenicity of conidia on isolated and living leaves.
The experiment on isolated leaves showed that the average lesion diameter of the control group was 10.3 mm, while the diameter of the treatment group was only 2.8 mm.The experiment on living leaves showed 24 lesions on average per leaf in the control group and 6 lesions on average per leaf in the treatment group.
See this image and copyright information in PMC

References

    1. Zhang H, Wu Z, Wang C, Li Y, Xu JR. Germination and infectivity of microconidia in the rice blast fungus Magnaporthe oryzae. Nature Communications. 2014;5:4518 10.1038/ncomms5518 - DOI - PMC - PubMed
    1. Xiong ZQ, Tu XR, Wei SJ, Huang L, Li XH, Lu H, et al. In vitro antifungal activity of antifungalmycin 702, a new polyene macrolide antibiotic, against the rice blast fungus Magnaporthe grisea. Biotechnology Letters. 2013;35(9):1475 10.1007/s10529-013-1229-z - DOI - PubMed
    1. Li Q, Jiang Y, Ning P, Zheng L, Huang J, Li G, et al. Suppression of Magnaporthe oryzae by culture filtrates of Streptomyces globisporus JK-1. Biological Control. 2011;58(2):139–48.
    1. Ohtaka N, Kawamata H, Narisawa K. Suppression of rice blast using freeze-killed mycelia of biocontrol fungal candidate MKP5111B. Journal of General Plant Pathology. 2008;74(2):101–8.
    1. Hyakumachi M, Takahashi H, Matsubara Y, Someya N, Shimizu M, Kobayashi K, et al. Recent studies on biological control of plant diseases in Japan. Journal of General Plant Pathology. 2014;80(4):287–302.

Publication types

MeSH terms

Supplementary concepts