Measurement and analysis of the ethylene production of the whole tomato pretreated by different concentrations of 1-MCP, Cryptococcus. laurentii, or the combined treatment
Description
The ethylene inhibitor, 1-methylcyclopropene (1-MCP) suppresses ethylene responses through its higher binding affinity to the ethylene receptors than ethylene. Cryptococcus laurentii is a well-known antagonistic yeast that can remarkably induce resistance in pears, jujube fruits, peaches, table grapes and cherry tomato (J. Lai, Cao, Yu, Wang, Zhang, Zheng, et al., 2018), and reduce postharvest fungal diseases in fruits, such as peach, pear, apple (Wei, Xu, Wu, Tu, Pan, & Tu, 2016), cherry tomato (C. F. Zhang, Chen, & Wang, 2013) and strawberry (X. Y. Zhang, Sun, Yang, Chen, Li, & Zhang, 2015). Therefore, the article aimed to evaluate ethylene production of the whole tomato fruit pretreated by different concentrations of 1-MCP, C. laurentii, or the combined treatment.
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Fruit pretreatment and microorganisms Mature red cherry tomatoes (Solanum lycopersicum var. cerasiforme) of the cultivar ‘QianXi’ without injuries or infections were hand-harvested during the red stage from Hainan Lingshui Modern Agriculture Demonstration Base in Lingshui country, Hainan Province, China, and immediately transported to our laboratory in Zhejiang University. The fruits were chosen based on size uniformity and ripeness, and then surface-sterilized in 0.1% (v/v) sodium hypochlorite aqueous solution for 2 min, rinsed thoroughly with tap water, and air-dried at 20℃ prior to the experiment. The yeast strain C. laurentii (Kufferath) Skinner (Strain zju 10) was originally isolated from pear fruit and cultured in 250-mL flasks containing nutrient yeast dextrose broth (NYDB). After incubation in a gyratory shaker at 28°C for 24 h, the yeast cells were collected by spinning at 4000 g for 10 min, washed twice, and re-suspended in sterile-distilled water. Then, the number of yeast cells was determined using a hemocytometer, and the concentration was adjusted to 1×108 cells mL-1. Determination of ethylene production The cherry tomato fruits were fumigated with either 1-MCP gas at concentrations of 0.5, 1, 5 and 10 μL L-1 or air (as control) (Bomei biotechnology. Co., Ltd, Heifei, China) before yeast induction. 1-MCP was released by dissolving a defined amount of the compound in 10 mL sterile-distilled water, which was immediately put into the containers. The treatments were performed at 25°C for 18 h in sealed 36 L jars (100 cherry tomato fruits per jar). The ethylene production of tomato fruits prefumigated with different concentrations of 1-MCP gases or with concentration of 5 μL L-11-MCP gases after C. laurentii induction (the tomato fruits were dipped in either sterile distilled water (control) or 1×108 cells mL-1 suspension of C. laurentii for 10 min) was determined at 0, 12, 24 and 48 h. The weight and volume of three replicates (4 tomatos per replicate) from 100 tomato fruits per treatment were recorded. They were sealed in a 0.25 L glass container at 25°C and incubated for 2 h. The ethylene production was determined using the method by Lu et al. (Lu, Xu, Zeng, Zheng, & Yu, 2014) with slight modification. About 1mL of the head space gas from each glass jar was sucked out and injected into the gas chromatograph (GC-2014C, Shimadzu Co., Ltd., Kyoto, Japan) equipped with a 2000 × 3 mm stainless-steel column of aluminum oxide. The carrier gas was N2, and the temperature of the flame ionization detector (FID), column and injector were 150, 85 and 140°C, respectively. The results were expressed in nLg-1h-1. The calculating formula is described as follows: Ethylene production（nl•g^(-1)•h^(-1) ）=(C×（V_1-V_2）×H)/(W×h×H_0 )