Table 1.
Morphological and biochemical characteristics of the bacterial stain QBA5.
Fig 1.
Cell-free supernatant of QBA5 significantly inhibited conidia germination and germ tube growth of B. cinerea.
A: The germination rate of B. cinerea conidia after 8 h incubation with different concentrations of the cell-free supernatant of QBA5 at 23°C. B: Germ tube growth of B. cinerea at two time points after incubation with different concentrations of the cell-free supernatant of QBA5 at 23°C. Columns with different letters are significantly different. (p<0.01).
Table 2.
Inhibitory effect of the cell-free supernatant of QBA5 on the mycelial growth of B. cinerea (p<0.01).
Fig 2.
The cell-free supernatant of QBA5 destroyed plasma membrane integrity of B. cinerea.
A: Percentage of plasma membrane integrity of B. cinerea conidia. B: Microscopy images of B. cinerea conidia after 8 h incubation and stained with propidium iodide (PI). The images on the left were captured under bright field, and the images on the right were captured under excitation light field. a: Conidia suspended in distilled water as the control. b: Conidia treated with cell-free supernatant of QBA5. Bar = 20μm.
Fig 3.
The cell-free supernatant of QBA5 had dramatic inhibitory effects on conidia of Botrytis cinerea.
A: Conidia suspended in sterile distilled water as control. B: Conidia treated with the cell-free supernatant of QBA5 for 24 h. Bar = 10μm.
Fig 4.
The cell-free supernatant of QBA5 greatly inhibited disease severity not only in detached leaves but also fruits.
A: Disease severity of gray mold on tomato leaves. 1 and 4: leaves treated with cell-free supernatant of QBA5. 2: Leaves treated with YEPD as the negative control. 3: Leaves treated with Methylthio diethofencarb (667mg/L) as the positive control. B: Disease severity of gray mold on tomato fruits. a: Tomato fruit treated with YEPD as the negative control. b: Tomato fruit treated with the cell-free supernatant of QBA5. c: Tomato fruit treated with Methylthio diethofencarb (667mg/L) as the positive control. Columns with different letters are significantly different. (p<0.05).
Table 3.
The preventive and curative effects of the QBA5 100% cell-free supernatant on the infection of B. cinerea on tomato plants.
Fig 5.
The bioactive compounds in the supernatant of QBA5 were separated with preparative high performance liquid chromatography (PHPLC).
Four distinct eluent peaks were detected at 3.10 min, 5.33 min, 7.07 min and 7.73 min by their ultraviolet absorption at 210 nm.
Fig 6.
The inhibitory effect of the four active compounds on the conidia germination of B. cinerea.
A, B, C, and D represent the compounds collected at 3.10 min, 5.33 min, 7.07 min and 7.73 min from the supernatant of QBA5 by preparative high performance liquid chromatography (PHPLC), respectively.