Fruit quality analysis and comprehensive evaluation of 18 Huyou (Citrus changshanensis) accessions

Abstract: 【Objective】Huyou (Citrus changshanensis K. S. Chen et C. X. Fu) is a local characteristic citrus resource in China. The main production area is in Changshan county, Quzhou City, Zhejiang province. Huyou has a history of commercial cultivation for over a hundred years, and now huyou has become a key industry of characteristic agriculture in Changshan county and an important source of income for local fruit growers. The evaluation of fruit quality is an important part of phenotypic characterization of huyou accessions, and also an important basis for screening excellent germplasm accessions. Currently in huyou, no systematic analysis and evaluation of fruit quality differences among different accessions have been carried out, and meanwhile, a comprehensive fruit quality evaluation system has not been developed, which impair the selection and industrial application of excellent accessions. The aim of this study was to comprehensively evaluate the fruit quality of huyou, to establish a fruit qualityevaluation system, and to provide a basis for the selection of high quality accessions.【Methods】Eighteen huyou accessions, with one typical tree for each accession, were involved in this study. For each tree, fifteen fruit evenly distributed in the crown were harvested when fruit were at commercial harvest maturity. A number of quality indicators, including the average fruit weight (AFW), fruit shape index (FSI), edible rate (ER), pericarp thickness, soluble solids content (SSC), titratable acid content (TAC), SSC/TAC ratio, vitamin C (Vc) content, flavanone neohesperidosides (FNs) content, flavanone rutinosides (FRs) content, and the contents of total phenolics, etc., were measured. SPSS and Excel were used for data analysis. Systematic description and sensory evaluation were used to analyze the fruit quality indicators such as peel appearance, flesh texture and peeling ability. The weights of quality indicators were determined by analytic hierarchy process (AHP), and the overall fruit quality of different accessions were evaluated and ranked by comprehensive score.【Results】The fruit quality of the 18 Huyou accessions varied in different degree, with coefficients of variation ranging from 3.07% to 143.57% for the different quality indicators analysed. Among all indicators, the number of seeds per fruit had the largest variation and the FSI had the smallest. The AFW ranged from 184.32 to 423.20 g, with Hongrou Huyou having the largest AFW and Guo 4 having the smallest. The longitudinal fruit diameter of all accessions was smaller than the transverse fruit diameter, and thus the FSI was less than 1, with an average of 0.89. Pericarp thickness and ER ranged from 2.15 to 9.68 mm and from 50.33% to 83.67%, respectively. The number of seeds per fruit varied greatly among the different accessions, with Cuihong having the lowest number, 0.22, while Guo 16 had the highest number, 22.67. SSC ranged from 9.83% to 15.40%, with Guo 4 being highest. TAC ranged from 0.90% to 1.57%, with Guo 8 having the highest TAC and Hongrou Huyou having the lowest. The SSC/TAC ratio varied widely among accessions, with the highest value of 12.73 for Guo 18 and the lowest value of 7.91 for Guo 7. The Vc content ranged from 35.88 to 72.95 mg · 100 g- 1 . Guo 10 had the highest content of FNs, a class of bitter flavonoids, while Cuihong had the highest content of FRs, a class of non-bitter flavonoids, but non-detectable FNs, in consistency with the bitter flavor feeling of different accessions. The total carotenoids varied greatly among different accessions with contents ranging from 2.29 to 8.66 μg · g-1 , and for the total phenolics, from 13.83 to 20.07 mg·g-1 . The peeling ability of the fruit varied widely with Huyou elite plant a, with Hongrou Huyou, Guo 2 and Guo 11 being the easiest. A comprehensive evaluation model of fruit quality was constructed by AHP analysis and the weights of each quality indicator were calculated by 1 to 9 scale method. In this evaluation model, sweetness and sourness were given the highest weight, 17.65%, and fruit shape index was given the lowest, 2.29%. Based on the average value, maximum value and minimum value of each indicator, the variation of each measured indicator was determined, and meanwhile, fruit quality indicators such as peel appearance, flesh texture and peeling ability were scored via systematic description and sensory evaluation. Finally, based on the score and the weight of each indicator, the accessions were evaluated for overall fruit quality. The results showed that 01-7b, 01-7a, Huyou elite plant b, Huyou elite plant a and Guo 5 were the top five accessions with excellent overall fruit quality. Moreover, Cuihong is an ideal resource for breeding low bitter Huyou while Guo 10 is probably favorable to be used as a raw resource for production of traditional Chinese medicine Quzhou Aurantii Fructus (Qu Zhi Qiao). These can satisfy the demand for diversity in consumption.【Conclusion】The fruit quality of the analyzed 18 different accessions varied greatly. On the basis of the external and internal qualities, an AHP method was used to comprehensively evaluate the fruit quality, and as a result, five accessions with excellent overall quality were selected. The method established in this study improves the accuracy and effectiveness for the comprehensive evaluation of the fruit quality of Huyou,and provides a reference for further selection and breeding of elite Huyou accessions.