Initial study on inhibition of Penicillium expansum by Pseudomonas sp. YL11 and mechanism

Abstract:

[Background] Apple blue mold rot is an important fruit post-harvest disease that caused by Penicillium expansum, which affects the quality of the fruit and leads to the rot of the apple resulting in economic losses. [Objective] To study the inhibitory effect and explore the inhibition mechanism of Pseudomonas sp. YL11 on P. expansum. [Methods] We studied the effects of cell-free fermentation filtrate of Pseudomonas sp. YL11 with different concentration on the growth colony diameter, spore germination, mycelial dry weight of P. expansum and the lesion diameter of wounded inoculated apple fruit; We also explored impact of the conductivity, nucleic acid and protein release, AKP content, SDH activity, ATPase activity and ATP content to reveal the inhibitory mechanism. [Results] Pseudomonas sp. YL11 sterile fermentation broth effectively inhibited the growth of P. expansum. The diameter of inhibition zone was 22.33±0.27 mm and the inhibition titer was 71.67 mm/mL. It also could effectively inhibit spore germination. The inhibition rate of 100% aseptic fermentation broth to germination reached 80.2%. It had certain inhibition effect on the biomass of P. expansum. The dry weight of mycelium was 4.7 mg/mL and the inhibition rate reached 39.74% when the volume fraction was 100%. Moreover, aseptic fermentation fluid effectively inhibited extension of lesion diameter of blue mold of apple. The maximum inhibitory rate reached 47.1% at 3 d. In addition, aseptic fermentation broth treatment increased electrical conductivity, intracellular nucleic acid, protein release, extracellular AKP content and decreased SDH activity, ATPase activity and ATP content. The effect was enhanced by the fermentation broth concentration. [Conclusion] Pseudomonas sp. YL11 disturbed the normal growth of P. expansum by significantly inhibited the growth of P. expansum, destroyed the structure of cell membrane and reduced the activity of energy metabolism enzyme. It had a good better biocontrol effect to against blue mold of apple and had a potential development value.