Elsevier

Food Chemistry

Volume 138, Issue 1, 1 May 2013, Pages 539-546
Food Chemistry

Burdock fructooligosaccharide induces fungal resistance in postharvest Kyoho grapes by activating the salicylic acid-dependent pathway and inhibiting browning

https://doi.org/10.1016/j.foodchem.2012.10.058Get rights and content

Abstract

Burdock fructooligosaccharide (BFO) is a natural elicitor from Arcitum lappa. The effects of BFO in controlling postharvest disease in grape, apple, banana, kiwi, citrus, strawberry, and pear were investigated. The disease index, decay percentage, and area under the disease progress curve indicated that BFO has general control effects on postharvest disease of fruits. Kyoho grapes were studied to elucidate the mechanism of BFO in boosting the resistance of grapes to Botrytis cinerea infection. BFO treatment induced upregulation of the npr1, pr1, pal, and sts genes, and inhibited the total phenol content decrease, which activated chitinase and β-1,3-glucanase. These results indicated that the salicylic acid-dependent signalling pathway was induced. The delayed colour change and peroxidase and polyphenoloxidase activity suggested that BFO delayed grape browning. The reduced respiration rate, weight loss, and titratable acidity prolonged the shelf life of postharvest grapes. BFO is a promising elicitor in postharvest disease control.

Highlights

► Common postharvest disease in seven kinds of fruits can be controlled by burdock fructooligosaccharide (BFO). ► A 29 percent AUDPC decrease of Botrytis cinerea in Kyoho grape has been observed. ► Salicylic acid-dependent signalling pathway and systemic acquired resistance have been activated by BFO in Kyoho grape. ► BFO delayed grape browning by delaying peroxidase and polyphenoloxidase activity in Kyoho grape skin. ► BFO restrained respiration rate, weight loss, and titratable acidity in Kyoho grape.

Introduction

Postharvest fruit losses are mainly attributed to decay caused by pathogen infection. Postharvest diseases can be controlled by synthetic fungicides (Tripathi & Dubey, 2004). However, the carcinogenicity and environmental pollution risk of fungicides has created an urgent need for new and effective technologies for controlling postharvest diseases with limited side effects. Inducing fruit systemic acquired resistance (SAR) with natural elicitors is an effective alternative. Chitooligosaccharides have been confirmed to be natural elicitors and can be derived from non-toxic and degradable biological materials with high efficiency (Holley, Yalamanchili, Moura, Ryan, & Stratmann, 2003). Postharvest diseases of pears, apples, watermelons, tomatoes, and carrots have been reported to be controlled by oligosaccharide elicitors (Meng et al., 2010, Molloy et al., 2004, Wang et al., 2009a, Yin et al., 2010). The control effects were due to induced systemic acquired resistance.

Kyoho grapes, a typical non-climacteric fruit, are an economically important grape cultivar in China. However, postharvest fungal disease caused by Botrytis cinerea, as well as browning, severely impact grape storage and transportation (Deng, Wu, & Li, 2006). It is critical to control fungal infection and browning to maintain the quality of postharvest Kyoho grapes. Chitosan has been reported to inhibit weight loss, increase the accumulation of phenol compounds and induce a series of resistance-related enzymes, such as peroxidase (POD), polyphenoloxidase (PPO), superoxide dismutase (SOD), and phenylalanine ammonia-lyase (PAL) in postharvest fruits (Meng, Li, Liu, & Tian, 2008). However, the molecular mechanism of elicitor-induced resistance in postharvest grapes remains unclear.

Burdock fructooligosaccharide (BFO) was first isolated from the root tissue of Arcitum lappa (Hao, Chen, Zhong, Chen, & Li, 2005). This compound is composed of a linear chain of twelve β-(21)-linked fructofuranose residues with a single terminal α-(1  2)-linked glucopyranose. BFO has no known anti-microbial activities, but it can increase the resistance of tomatoes to B. cinerea (He, Li, Chen, Hao, & Li, 2006), that of cucumbers to Colletotrichum orbiculare (Zhang, Wang, Liu, & Chen, 2009), and that of tobacco to the tobacco mosaic virus (Wang, Feng, & Chen, 2009b). BFO also increased PR1, PR2, PR3, and PAL gene expression in tomatoes (Wang et al., 2009a).

In this study, the general effects of BFO in controlling postharvest disease in different fruits were examined. We then focused on Kyoho grapes to elucidate the mechanism of BFO in increasing the resistance of grapes to B. cinerea infection and prolonging shelf life.

Section snippets

BFO preparation

BFO was extracted according to previously described methods (Hao et al., 2005). Briefly, roots of A. lappa were sliced and placed in 95 °C water for 2 h. Next, the extracted solution was precipitated with ethanol, deproteinised with chloroform, decoloured using a resin column, and separated and purified by molecular exclusion chromatography. The BFO solution (0.5% w/v) was dissolved in sterile distilled water.

Fruit and pathogen

Fruits (Table 1) were transported to our laboratory within 48 h after harvest and

BFO increased resistance of various types of postharvest fruits

The disease index Figures (Fig. 1) showed that the disease development kinesis was different between climacteric fruit and non-climacteric fruit. A dramatic disease index increase in a short time period was observed in climacteric fruit, such as apples (Fig. 1A, from 29% to 50% on the 4th day), bananas (Fig. 1C, from 36% to 53% on the 4th day), kiwifruit (Fig. 1E, from 24% to 47% on the 4th day), and pears (Fig. 1G, from 33% to 58% on the 2nd day). Non-climacteric fruit, such as grapes (Fig. 1

Discussion

Broad-spectrum protection against postharvest diseases has been confirmed using chitosan (Bautista-Baños et al., 2006). The same as a natural elicitor, BFO treatment reduced B. cinerea infection in grapes and kiwifruit, Penicillium expansum infection in apples, Penicillium italicum infection in citrus, Calletotrichum musae infection in bananas, and natural diseases in strawberries and Bartlett pears. The AUDPC (area under the disease progress curve) method was used to measure the control

Acknowledgement

This work was supported by the National High Technology Research and Development Program of China (2007AA10Z334).

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