Article pubs.acs.org/JAFC
Benzothiadiazole-Mediated Induced Resistance to Colletotrichum musae and Delayed Ripening of Harvested Banana Fruit Xiaoyang Zhu,† Huanzhang Lin,†,‡ Zhenwei Si,† Yihua Xia,†,§ Weixin Chen,† and Xueping Li*,† †
State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources/Guangdong Provincial Key Laboratory for Postharvest Science and Technology of Fruits and Vegetables, College of Horticulture, South China Agricultural University, Guangzhou 510642, P. R. China ‡ School of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou 510006, P. R. China § Hainan University, Haikou, Hainan Province 570228, P. R. China ABSTRACT: Benzothiadiazole (BTH) works as a plant activator. The effects of different BTH treatments and fungicides SPORGON on fruit ripening and disease incidence were investigated. The results showed that BTH treatment significantly delayed fruit ripening, maintained fruit firmness, color, and good fruit quality, and dramatically reduced the incidence of disease. BTH effectively inhibited the invasion and development of pathogenic bacteria and controlled the occurrence of disease. BTH treatment enhanced the activities of defense-related enzymes, including chitinase, phenylalanine ammonia-lyase, peroxidase, and polyphenol oxidase, increased the content of hydrogen peroxide and total antioxidant capacity, and reduced malondialdehyde content. Cellular structure analysis after inoculation confirmed that BTH treatment effectively maintained the cell structural integrity. SPORGON did not provide benefits for delaying fruit ripening or for the resistance system, while it can control the disease only during the earlier stage and not at later stages. KEYWORDS: BTH, fruit ripening, disease incidence, disease resistance, cell integrity
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INTRODUCTION Significant decay losses take place after harvest, during storage and marketing of fresh fruit. Most fresh fruit perish very quickly. Without being handled properly after being harvested and while being transported, they will decay soon and become unsuitable for human consumption. Microbially caused decay is one of the key factors that determine losses. New fungicides and modern storage technologies have been extensively studied to extend the shelf life of fresh fruit and reduce postharvest losses.1 Preharvest treatments with synthetic fungicides remain one of the main means for postharvest disease control.2 However, a common concern about the negative impact of fungicide residues on the environment and public health has considerably limited the use of fungicides after harvest. Extensive research has been conducted in recent years to reduce the heavy dependence on chemical fungicides to control postharvest diseases and disorders of horticultural crops. In addition to synthetic fungicides, alternative strategies have also attracted an increasing amount of interest because of their lower cost, lower risk of development of fungal resistance, and a less negative impact of agriculture on the environment and human health,3,4 which were based on improved cultural practices, biological control, plant-defense promoters, and physical treatments.1,4 Among the recent new strategies, disease resistance induced by an eco-friendly elicitor in horticultural crops has attracted a great deal of interest because of its ecological compatibility.5 Various elicitors such as avirulent pathogens, plant extracts, phytohormones (ethylene, salicylic acid, jasmonic acid, abscisic acid, and indole acetic acid), etc., can effectively activate a wide range of defense responses.6 Benzothiadiazole (BTH) is a functional analogue of the plant signal molecule, salicylic acid © XXXX American Chemical Society
(SA), and one kind of plant activators that protect various plants from infectious diseases.7,8 BTH has been reported to have dual effects in plant protection, which inhibits the development of decay-causing fungi through its direct toxicity on one hand and induces the establishment of systemic acquired resistance (SAR) in a variety of plants on the other.2,6,8,9 At present, studies have shown that the effectiveness of BTH in protecting different plant species against diseases caused by viral, bacterial, and fungal pathogens.10−12 Recently, BTH has been applied to enhance disease resistance on strawberries,13 grape fruit,14 peach fruit,12 muskmelon fruit,15 grape berries,6 mango fruit,16 papaya fruit,17 and banana.18 However, the mechanism underlying BTH-induced disease resistance is not so clear in fruit, especially in banana fruit. In this work, we tested the effects of different BTH treatments and a fungicide, SPORGON, on fruit ripening and disease incidence. A wounded inoculation experiment was conducted to study the response of the fruit to the bacteria. Several key defense-related enzymes, including chitinase (CT), phenylalanine ammonia-lyase (PAL) and peroxidase (POD), and polyphenol oxidase (PPO), and the redox-related indicators, hydrogen peroxide (H2O2) level, total antioxidant capacity (T-AOC), and malondialdehyde (MDA) content, were tested. Cellular and structural changes after inoculation with Colletotrichum musa were examined to reveal any new insights into the defense responses. The aim was to gain new insights Received: November 30, 2015 Revised: January 25, 2016 Accepted: January 30, 2016
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DOI: 10.1021/acs.jafc.5b05655 J. Agric. Food Chem. XXXX, XXX, XXX−XXX
Article
Journal of Agricultural and Food Chemistry
proportion of the stem-end portion affected with disease is
