Plant Growth Promotion and Biocontrol of Leaf Blight Caused by Nigrospora sphaerica on Passion Fruit by Endophytic Bacillus subtilis Strain GUCC4

Junrong Wang^{1

2

3

4}, Shun Qin^{1

2

3}, Ruidong Fan^{1

2

3}, Qiang Peng^{1

2

3}, Xiaojing Hu^{1

2

3}, Liu Yang⁵, Zengliang Liu⁶, Ivan Baccelli⁷, Quirico Migheli⁸, Gabriele Berg⁹, Xiaoyulong Chen^{1

2

3

4}, Tomislav Cernava^{1

9}

Affiliations

¹ College of Agriculture, College of Tobacco Science, Guizhou University, Guiyang 550025, China.
² International Jointed Institute of Plant Microbial Ecology and Resource Management in Guizhou University, Ministry of Agriculture, China Association of Agricultural Science Societies, Guizhou University, Guiyang 550025, China.
³ Guizhou-Europe Environmental Biotechnology and Agricultural Informatics Oversea Innovation Center in Guizhou University, Guizhou Provincial Science and Technology Department, Guiyang 550025, China.
⁴ College of Ecology and Environment, Tibet University, Lhasa 850012, China.
⁵ Guangxi Crop Genetic Improvement Biotechnology Laboratory, Nanning 530007, China.
⁶ Microbiology Research Institute, Guangxi Agricultural Science Academy, Nanning 530007, China.
⁷ Institute for Sustainable Plant Protection, National Research Council of Italy (CNR), 50019 Sesto Fiorentino, Italy.
⁸ Dipartimento di Agraria and NRD-Nucleo di Ricerca sulla Desertificazione, Università degli Studi di Sassari, 07100 Sassari, Italy.
⁹ Institute of Environmental Biotechnology, Graz University of Technology, 8010 Graz, Austria.

PMID: 36836247
PMCID: PMC9966402
DOI: 10.3390/jof9020132

Plant Growth Promotion and Biocontrol of Leaf Blight Caused by Nigrospora sphaerica on Passion Fruit by Endophytic Bacillus subtilis Strain GUCC4

Junrong Wang et al. J Fungi (Basel). 2023.

. 2023 Jan 18;9(2):132.

doi: 10.3390/jof9020132.

Authors

Affiliations

¹ College of Agriculture, College of Tobacco Science, Guizhou University, Guiyang 550025, China.
² International Jointed Institute of Plant Microbial Ecology and Resource Management in Guizhou University, Ministry of Agriculture, China Association of Agricultural Science Societies, Guizhou University, Guiyang 550025, China.
³ Guizhou-Europe Environmental Biotechnology and Agricultural Informatics Oversea Innovation Center in Guizhou University, Guizhou Provincial Science and Technology Department, Guiyang 550025, China.
⁴ College of Ecology and Environment, Tibet University, Lhasa 850012, China.
⁵ Guangxi Crop Genetic Improvement Biotechnology Laboratory, Nanning 530007, China.
⁶ Microbiology Research Institute, Guangxi Agricultural Science Academy, Nanning 530007, China.
⁷ Institute for Sustainable Plant Protection, National Research Council of Italy (CNR), 50019 Sesto Fiorentino, Italy.
⁸ Dipartimento di Agraria and NRD-Nucleo di Ricerca sulla Desertificazione, Università degli Studi di Sassari, 07100 Sassari, Italy.
⁹ Institute of Environmental Biotechnology, Graz University of Technology, 8010 Graz, Austria.

PMID: 36836247
PMCID: PMC9966402
DOI: 10.3390/jof9020132

Abstract

Passion fruit (Passiflora edulis Sims) is widely cultivated in tropic and sub-tropic regions for the production of fruit, flowers, cosmetics, and for pharmacological applications. Its high economic, nutritional, and medical values elicit the market demand, and the growing areas are rapidly increasing. Leaf blight caused by Nigrospora sphaerica is a new and emerging disease of passion fruit in Guizhou, in southwest China, where the unique karst mountainous landscape and climate conditions are considered potential areas of expansion for passion fruit production. Bacillus species are the most common biocontrol and plant-growth-promotion bacteria (PGPB) resources in agricultural systems. However, little is known about the endophytic existence of Bacillus spp. in the passion fruit phyllosphere as well as their potential as biocontrol agents and PGPB. In this study, 44 endophytic strains were isolated from 15 healthy passion fruit leaves, obtained from Guangxi province, China. Through purification and molecular identification, 42 of the isolates were ascribed to Bacillus species. Their inhibitory activity against N. sphaerica was tested in vitro. Eleven endophytic Bacillus spp. strains inhibited the pathogen by >65%. All of them produced biocontrol- and plant-growth-promotion-related metabolites, including indole-3-acetic acid (IAA), protease, cellulase, phosphatase, and solubilized phosphate. Furthermore, the plant growth promotion traits of the above 11 endophytic Bacillus strains were tested on passion fruit seedlings. One isolate, coded B. subtilis GUCC4, significantly increased passion fruit stem diameter, plant height, leaf length, leaf surface, fresh weight, and dry weight. In addition, B. subtilis GUCC4 reduced the proline content, which indicated its potential to positively regulate passion fruit biochemical properties and resulted in plant growth promotion effects. Finally, the biocontrol efficiencies of B. subtilis GUCC4 against N. sphaerica were determined in vivo under greenhouse conditions. Similarly to the fungicide mancozeb and to a commercial B. subtilis-based biofungicide, B. subtilis GUCC4 significantly reduced disease severity. These results suggest that B. subtilis GUCC4 has great potential as a biological control agent and as PGPB on passion fruit.

Keywords: antagonisms; endophytic Bacillus; enzyme activity; passion fruit; plant growth promotion.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

**Figure 1**
Inhibition of *N. sphaerica* by 11 *Bacillus* strains in comparisons to the control, synthetic fungicide mancozeb, and reference strain *B. subtilis* NCD_2. Treatments, (ck): control, (a): mancozeb, (b): *B. subtilis* NCD_2, (c): *B. subtilis* GUCC8, (d): *B. subtilis* GUCC4, (e): *B. cereus* GUCC7, (f): *B. cereus* GUCC3, (g): *B. cereus* GUCC6, (h): *B. cereus* GUCC9, (i): *B. cereus* GUCC11, (j): *B. cereus* GUCC2, (k): *B. cereus* GUCC5, (l): *B. cereus* GUCC1001, (m): *B. cereus* GUCC10.

**Figure 2**
Phylogenetic tree based on 16S rRNA (A) gene and *gyr*B (B) gene sequences. The strains from this study were highlighted in bold.

**Figure 3**
(A). Inhibition of *N. sphaerica* by volatile compounds of 11 Bacillus strains treatments, ck: control, a: *B. subtilis* GUCC8, b: *B. subtilis* GUCC4, c: *B. cereus* GUCC7, d: *B. cereus* GUCC3, e: *B. cereus* GUCC6, f: *B. cereus* GUCC9, g: *B. cereus* GUCC11, h: *B. cereus* GUCC2, i: *B. cereus* GUCC5, j: *B. cereus* GUCC1001, k: *B. cereus* GUCC10. (B). Inhibition of *N. sphaerica* by culture filtrate of 11 Bacillus strains treatments, ck: control, a: *B. subtilis* GUCC8, b: *B. subtilis* GUCC4, c: *B. cereus* GUCC7, d: *B. cereus* GUCC3, e: *B. cereus* GUCC6, f: *B. cereus* GUCC9, g: *B. cereus* GUCC11, h: *B. cereus* GUCC2, i: *B. cereus* GUCC5, j: *B. cereus* GUCC1001, k: *B. cereus* GUCC10. (C). Inhibition of *N. sphaerica* by culture filtrate of 11 Bacillus strains. Data in the table are presented as the means ± standard deviation. Different letters in the same column indicate statistical significance (p < 0.05).

**Figure 4**
The effects of different Bacillus strains on total chlorophyll content (A), SOD (B), POD (C), CAT (D) enzyme activities, total MDA (E), and Pro content (F) in passion fruit leaves. All data represents the means ± standard deviation for three biological replicates. Values with different letters in the same column indicate statistical significance (p < 0.05).

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Plant Growth Promotion and Biocontrol of Leaf Blight Caused by Nigrospora sphaerica on Passion Fruit by Endophytic Bacillus subtilis Strain GUCC4

Affiliations

Plant Growth Promotion and Biocontrol of Leaf Blight Caused by Nigrospora sphaerica on Passion Fruit by Endophytic Bacillus subtilis Strain GUCC4

Authors

Affiliations

Abstract

Conflict of interest statement

Figures

References

Grants and funding

LinkOut - more resources

Full Text Sources

Molecular Biology Databases

Miscellaneous