Protective effect of Polygonum orientale L. extracts against Clavibater michiganense subsp. sepedonicum, the causal agent of bacterial ring rot of potato.

Jin Cai,Jia Feng,Feipeng Wang,Qiufeng Xu,Shulian Xie

doi:10.1371/journal.pone.0068480

Abstract

The Polygonum orientale L. extracts were investigated for antibacterial activity against Clavibater michiganense subsp. sepedonicum (Spieckermann & Kotthoff) Davis et al., the causal agent of a serious disease called bacterial ring rot of potato. The results showed that the leaf extracts of P. orientale had significantly (p<0.05) greater antibacterial activity against C. michiganense subsp. sepedonicum than root, stem, flower extracts in vitro. According to the results of single factor experiments and L273(13) orthogonal experiments, optimum extraction conditions were A1B3C1, extraction time 6 h, temperature 80°C, solid to liquid ratio 1∶10 (g:mL). The highest (p<0.05) antibacterial activity was observed when pH was 5, excluding the effect of control. The extracts were stable under ultraviolet (UV). In vivo analysis revealed that 50 mg/mL of P. orientale leaf extracts was effective in controlling decay. Under field conditions, 50 mg/mL of P. orientale leaf extracts also improved growth parameters (whole plant length, shoot length, root length, plant fresh weight, shoot fresh weight, root fresh weight, dry weight, and number of leaves), in the 2010 and 2011 two growing seasons. Further solvent partition assays showed that the most active compounds were in the petroleum ether fractionation. Transmission electron microscopy (TEM) showed drastic ultrastructural changes caused by petroleum ether fractionation, including bacterial deformation, electron-dense particles, formation of vacuoles and lack of cytoplasmic materials. These results indicated that P. orientale extracts have strong antibacterial activity against C. michiganense subsp. sepedonicum and a promising effect in control of bacterial ring rot of potato disease.

Highlights

Clavibater michiganense subsp. sepedonicum (Spieckermann & Kotthoff) Davis et al, is a causal agent of a serious disease called bacterial ring rot of potato
Maximum (p,0.05) extraction yield of antibacterial substances was achieved at 1:15 ratio, antibacterial activity decreased with increasing ratio (Figure 2 C)
It has become clear that petroleum ether fractionation of P. orientale extracts showed the greatest potential to inhibit the growth of C. michiganense subsp. sepedonicum

Summary

Introduction

Clavibater michiganense subsp. sepedonicum (Spieckermann & Kotthoff) Davis et al, is a causal agent of a serious disease called bacterial ring rot of potato. Chemical bactericides e.g. quaternary ammonia, bleach, chlorine dioxide, copper sulfate, potassium permanganate, iodine and phenol groups, are the most commonly used methods for controlling bacterial ring rot of potato [5,6,7]. These chemicals have the potential to exert toxic effects on humans and wildlife as well as to cause environment pollution [8]. There are few reports available in the literature on the biological prevention and control of C. michiganense subsp. sepedonicum using plant extracts

Methods

Results

Discussion

Conclusion