Chitosan primes plant defence mechanisms against Botrytis cinerea, including expression of Avr9/Cf-9 rapidly elicited genes.

Daniel De Vega,Estrella Luna,Nicola Holden,Pete E Hedley,Adrian Newton,Jenny Morris

doi:10.1111/pce.13921

Abstract

Current crop protection strategies against the fungal pathogen Botrytis cinerea rely on a combination of conventional fungicides and host genetic resistance. However, due to pathogen evolution and legislation in the use of fungicides, these strategies are not sufficient to protect plants against this pathogen. Defence elicitors can stimulate plant defence mechanisms through a phenomenon known as defence priming. Priming results in a faster and/or stronger expression of resistance upon pathogen recognition by the host. This work aims to study defence priming by a commercial formulation of the elicitor chitosan. Treatments with chitosan result in induced resistance (IR) in solanaceous and brassicaceous plants. In tomato plants, enhanced resistance has been linked with priming of callose deposition and accumulation of the plant hormone jasmonic acid (JA). Large‐scale transcriptomic analysis revealed that chitosan primes gene expression at early time‐points after infection. In addition, two novel tomato genes with a characteristic priming profile were identified, Avr9/Cf‐9 rapidly elicited protein 75 (ACRE75) and 180 (ACRE180). Transient and stable over‐expression of ACRE75, ACRE180 and their Nicotiana benthamiana homologs, revealed that they are positive regulators of plant resistance against B. cinerea. This provides valuable information in the search for strategies to protect Solanaceae plants against B. cinerea.

Highlights

Crop yield losses of 20–40% of total agriculture productivity can be attributed to pests and diseases (Oerke, 2006; Savary, Ficke, Aubertot, & Hollier, 2012)
We have identified a formulation of chitosan that unlike some other formulations, can be dissolved in water and does not require infiltration
Treatments with chitosan resulted in induced resistance (IR) in S. lycopersicum (Figure 1a), S. melongena (Figure S1), Arabidopsis (Figure 1b) and N. benthamiana (Figure 4a) at a range of concentrations, which indicates that there are similar defence mechanisms acting in the response to fungal PAMPs

Summary

| INTRODUCTION

Crop yield losses of 20–40% of total agriculture productivity can be attributed to pests and diseases (Oerke, 2006; Savary, Ficke, Aubertot, & Hollier, 2012) Of these threats, the pathogen Botrytis cinerea causes annual losses of $10–$100 billion, as it reduces crop yield before harvest or leads to waste and spoilage post-harvest. Plant endogenous defences are activated by elicitor molecules resulting in induced resistance (IR) (Mauch-Mani, Baccelli, Luna, & Flors, 2017), since they are able to mimic pathogen-inducible defence mechanisms (Aranega-Bou, De La O Leyva, Finiti, García-Agustín, & González-Bosch, 2014). Different studies have shown that its effect on crop protection results from induction of defence mechanisms (Sathiyabama, Akila, & Einstein Charles, 2014) and direct antimicrobial activity (Goy, Britto, & Assis, 2009). Together with the outlined characteristics of chitosan, make this substance a suitable candidate for extensive application as a component of Integrated Pests (and disease) Management (IPM) for the protection of crops against fungal pathogens

| MATERIAL AND METHODS

| RESULTS

Findings

| DISCUSSION