Sodium alginate potentiates antioxidant defense and PR proteins against early blight disease caused by Alternaria solani in Solanum lycopersicum Linn.

Priya Dey,Ramani Ramanujam,Ganesan Venkatesan,Radhakrishnan Nagarathnam,Partha Mukhopadhyay

doi:10.1371/journal.pone.0223216

Abstract

The use of biopolymers as elicitors in controlling plant diseases is gaining momentum world-wide due to their eco-friendly and non-toxic nature. In the present study, we have used an algal biopolymer (sodium alginate) and tested its applicability as an elicitor in inducing resistance factors against Alternaria solani, which causes early blight disease in Solanum lycopersicum (tomato plant). We have pre-treated tomato plants with different concentrations of sodium alginate (0.2%, 0.4%, and 0.6%) before A. solani infection. We found that sodium alginate has effectively controlled the growth of A. solani. In addition, a significant increase in the expression levels of SOD was observed in response to pathogen infection. The increased protease inhibitors activity further suggest that sodium alginate restrict the development of A. solani infection symptoms in tomato leaves. This corroborates well with the cell death analysis wherein increased sodium alginate pre-treatment results in decreased cell death. Also, the expression profile analyses reveal the induction of genes only in sodium alginate-pretreated tomato leaves, which are implicated in plant defense mechanism. Taken together, our results suggest that sodium alginate can be used as an elicitor to induce resistance against A. solani in tomato plants.

Highlights

Plants have evolved with a variety of defense mechanisms to resist pathogen invasion, e.g., the activation of systemic acquired resistance (SAR) that protects the host plant against a wide range of pathogens [1,2]
The tomato plants were pretreated by spraying different sodium alginate concentrations, i.e., 0.2%, 0.4%, and 0.6%, on their leaves, while the control plants were pretreated with water, followed by A. solani inoculation
The results further demonstrate that foliar spray with 0.6% sodium alginate conferred the most significant resistance against A. solani (Fig 1H)

Summary

Introduction

Plants have evolved with a variety of defense mechanisms to resist pathogen invasion, e.g., the activation of systemic acquired resistance (SAR) that protects the host plant against a wide range of pathogens [1,2]. The onset of SAR is manifested by the accumulation of novel proteins called pathogenesis-related proteins that are expressed by the host plants in response to pathological or related situations. They have been found to enhance the defensive capacity of plants in response to necrotic infections [4]. The primary defense response in the host plant against a pathogen involves the rapid generation of reactive oxygen species (ROS), known as oxidative burst.

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