Bacterial antagonists and hexanal-induced systemic resistance of mango fruits against Lasiodiplodia theobromae causing stem-end rot

Parthasarathy Seethapathy,Thiribhuvanamala Gurudevan,Kizhaeral S Subramanian,Prabakar Kuppusamy

doi:10.1080/17429145.2016.1252068

Parthasarathy Seethapathy, Thiribhuvanamala Gurudevan + Show 2 more

Open Access

https://doi.org/10.1080/17429145.2016.1252068

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Abstract

ABSTRACTInduction of defense-related enzymes, such as phenylalanine ammonia lyase (PAL), peroxidase (PO), polyphenol oxidase (PPO), superoxide dismutase (SOD) and catalase (CAT) due to bacterial antagonists viz., Pseudomonas fluorescens (Pf1) and Bacillus subtilis (EPCO16) and plant-derived lipoxygenase volatile compound hexanal, were studied in mango fruits against Lasiodiplodia theobromae causing stem-end rot disease. The results showed increased induction of all the defense-related enzymes in mango fruits 3–5 days after dipping treatment with combination of bacterial antagonists and hexanal when compared to untreated control treatment and treatment with fungicide carbendazim in storage condition. The increased activity was observed up to 3 days after treatment and thereafter declined. Further, increased expression of specific isoforms of PO, PPO, SOD and CAT were also observed in the treatment effect of P. fluorescens (0.5%) + hexanal (0.02%) treated fruits against L. theobromae. From the results obtained, it is inferred that due to the enhancement of defense-related enzymes via the phenylpropanoid pathway and due to secretion of secondary metabolites that would play significant role in hindering the pathogen quiescence and further invasion in mango fruits and thereby prevent the fruit rot.

Highlights

The mango (Mangifera indica L.), belongs to the Anacardiaceae family, is one of the world’s most important and reputable fruits and is widely known as the ‘King of fruits’ (Purseglove 1972)
The results of in vitro screening, colorimetric assay and isoform analysis revealed that combinatorial application of P. fluorescens (Pf1) and lipoxygenase hexanal significantly inhibited the pathogen growth and increased activities of defense-related enzymes viz., phenylalanine ammonia lyase (PAL), PO, polyphenol oxidase (PPO), superoxide dismutase (SOD) and CAT in the mango fruits against postharvest stem-end rot disease under storage condition
Significant increase in the PAL activity was observed in the fruits which were dipped in 0.5% P. fluorescens (Pf1) + 2% hexanal cross inoculated with L. theobromae (0.28) simultaneously followed by dipping in 0.5% P. fluorescens (Pf1) and dipping in 0.5% B. subtilis (EPCO16) + 2% hexanal (0.24) on 3rd day after treatment, when compared to healthy control (0.14)

Summary

Introduction

The mango (Mangifera indica L.), belongs to the Anacardiaceae family, is one of the world’s most important and reputable fruits and is widely known as the ‘King of fruits’ (Purseglove 1972). (Griffon & Maubl.) is the most important one (Johnson & Coates 1993) This stem-end rot disease can render the fruits completely ineffective as it destroys the developed or developing fruits in storage condition. The efficacy of hexanal as a metabolizable organic fungicide and the improvement of the aroma production by the interconversion to other aroma volatiles in minimally processed apples (Song et al 1998). It positively overwhelmed the shelf life by reducing the growth of natural occurring pathogen population during storage at 4°C and 15°C (Lanciotti et al 2004). Hexanal is commercially approved safer food additive by the U.S food and drug administration program on everything added to food in the United States and has an ORL-MAM LD50 of 3700 mg kg−1 (Thavong et al 2011)

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