Characterization and evaluation of Staphylococcus sp. strain LZ16 for the biological control of rice blast caused by Magnaporthe oryzae

• Staphylococcus LZ16 showed strong antagonism against rice blast pathogen Magnaporthe oryzae.
• The lysate inhibits M. oryzae at optimum pH and temperatures in vitro.
• Staphylococcus LZ16 dramatically reduced the blast development in the fields.
• Expression of PNP significantly inhibited the extension of germ tube in M. oryzae.
• The strain had no any adverse impacts on the environment.

Staphylococcus sp. strain LZ16 was isolated from seawater collected in the East China Sea. Both culture filtrate and cell lysate of LZ16 possessed strong growth inhibition activities against Magnaporthe oryzae. Morphological observations revealed that conidial germination, germ tube elongation, appressorium formation were significantly inhibited after the treatment with cell lysate of LZ16. The active substances remained stable at temperature from 7 to 45 °C, and pH from 6 to 8. One of the fractions conferring strong fungistatic activities was separated using Phenyl-Sepharose CL-4B and Sephacryl S-200 High resolution columns, and identified as purine nucleoside phosphorylase (PNP) by Matrix-Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry. The gene deoD encoding PNP was cloned and expressed in Escherichia coli for the verification of the antagonistic activity against M. oryzae. This is the first report that PNP was associated with fungistatic activity. Field experiments showed that the extract of the bacterial culture prevented and alleviated the disease severity of M. oryzae infection compared to the level in the untreated control. The acute toxicity study revealed the lethal oral dose was more than 5000 mg/kg, and the adverse effect was not observed on both male and female rats after treatment for 14 days. All the results suggested that strain LZ16 and its bioactive substances might be promising candidates for biopesticide development, or transgenetic plant materials for the biocontrol of rice blast.

Cell lysate of Staphylococcus SP. LZ16 supressed pre-penetration stage of Magnaporthe oryzae. Microscopic observations of M. oryzae under different treatments. NC: PBS buffer (negative control); PC: tricyclazole (positive control).Figure optionsDownload as PowerPoint slide