Genetic diversity analysis of fruit quality traits using electronic nose and electronic tongue in apricot

Abstract: 【Objective】For a long time, the evaluation of fresh apricot fruit quality has been limited to the limited traits with limited materials, while the evaluation methods are limited to chemical and instrumental methods. The overall and rapid evaluation of apricot fruit quality traits from different groups is lacking. Therefore, we studied the genetic variation of aroma, taste and other fruit quality traits of a large population of apricot using rapid evaluation methods to select specific germplasm resources and provide theoretical basis for genetic improvement of fresh apricot.【Methods】In this study, 119 samples of apricot germplasm resources, which were sampled for two consecutive years, were used to measure fruit weight, soluble solid content, fruit firmness, the components of soluble sugar and organic acids, aroma and taste. The soluble sugars and organic acids were evaluated by High Performance Liquid Chromatography (HPLC). The aroma of apricot germplasm resources was evaluated by electronic nose technique (PEN3, AIRSENSE, Germany). The fruit taste of apricot was evaluated by electronic tongue technique (SA-402B, INSENT, Japan). The variation coefficient analysis, principal component analysis, correlation analysis and cluster analysis were carried out using Origin 2019 and SPSS 26 software.【Results】The coefficients of variation (CV) of 11 phenotypic traits ranged from 15.81% to 91.23%. The traits included fruit weight (FW), soluble solid content (SSC), fruit firmness (F), soluble sugar contentsincluding sucrose (SUC), glucose (GLU), fructose (FRU) and sorbitol (SOR) and organic acid components, including citric acid (CIT), malic acid (MAL), quinic acid (QUI) and shikimic acid (SHI). The CV of CIT content was the largest, and that of SSC was the smallest. The results of electronic nose measurement showed that the volatile substances of apricot germplasm resources were sensitive to W5S, W1S, W1W and W2W sensors, which indicated that the aroma substances of apricot mainly included sulfide, terpenes and alkanes. The results of electronic tongue determination of flavor substances in apricot germplasm resources showed that sour and sweet taste were the main tastes in apricot fruits. Through correlation analysis, it was found that firmness was significantly correlated with the content of sugar components, but not with the soluble solid content and the acid components content. The sweetness value was positively correlated with soluble solids content, GLU content, FRU content and SOR content, while negatively correlated with QUI, MAL and CIT content. Through principal component analysis (PCA), the contribution rate of the first 7 principal components reached 79.86%. The first principal component (PC1) represented the aroma characteristic of apricot, the second principal component (PC2) represented fruit taste related traits, and the third principal component (PC3) represented acid component content and fruit weight. The contribution rates of PC1, PC2 and PC3 were 28.36%, 17.36% and 12.33%, separately, and the cumulative contribution ratio of them was 58.05%. According to the principal component score table of each apricot variety, the varieties with high PC1 score had higher aroma response value and special fragrance, and Caotanmeixing, Shizixing, Kezilang and Baisaimaiti belonged to this group. A high PC2 score indicated varieties with high firmness, high sugar content, high sweetness, high umami and low acidity, including Harlayne, Ribenxing, Soganci, Maolaxiao, Kezikeximixi etc. A high PC3 score indicated a high content of acid components and a small fruit weight, and Huaxianchibangzi, Yingtiao, Sundrop, Betinka and Wangshizhong belonged to this group. According to the cluster analysis, when the genetic distance was 60, the remaining varieties except Caotanmeixing could be divided into two groups: The first group mainly included North China varieties, and the second group included other ecological group varieties. When the genetic distance was 40, group Ⅰ was further divided into 2 subgroups. The group Ⅱ could be further divided into four subgroups. Germplasm screening by comprehensive score of principal factors was an important method for objective evaluation on excellent germplasm resources. According to the proportion weight and contribution rate of different traits in each principal component, the score of each principal component and the comprehensive factor score of different varieties were calculated. Among 119 apricot germplasm resources, the top 10 germplasm materials were Caotanmeixing, Kumanti, Guantingerhuang, Tuohutikudayouxi, Mokeyouxi, Stela, Hacihaliloglu, Kezikeximixi, Kalayulüke and Soganci.【Conclusion】There are abundant genetic variations in apricot fruit quality traits such as aroma and taste. Electronic nose and electronic tongue can be used as a rapid evaluation method to identify aroma and taste characteristics of apricot. Eight excellent germplasm resources, including Caotanmeixing, Tuohutikudayouxi, Mokeyouxi, Stela, Hacihaliloglu, Kezikeximixi, Kalayulüke and Soganci, were selected to be used as parental materials for genetic improvement for fresh apricot.