Precise evaluation of different taste qualities of Chinese plum (Prunus salicina L.) germplasm

Abstract：【Objective】Chinese plum originated and has been cultivated for a long time in China. Precise germplasm evaluation is of great importance for germplasm innovation and breeding in fruit trees. The study focused on precise evaluation of the taste quality of different types of Chinese plum germplasms, including different geographic origins, flesh colors, and sensory taste perceptions in order to explore the genetic diversity of the taste quality and screen out excellent germplasm.【Methods】The test materials of 50 accessions of mature plum fruits were harvested in National Plum and Apricot Germplasm Repository during the ripe season in July to August in 2022 and 2023. Nine taste parameters were implemented with an electronic tongue, including freshness, saltiness, sourness, bitterness, astringency, sweetness, bitter aftertaste, astringent aftertaste, and richness. The objective patterns of taste quality genetics in Chinese plum germplasm were unveiled. For the analysis, 50 g mixed flesh from 10 peeled fruits of each accession were collected and diluted with 150 mL of distilled water in a test tube, and then shaken at 3000 r· min^-1 for 5 minutes. The SA-402B taste analysis system was used to accurately identify the taste richness of Chinese plums using six artificial lipid membrane sensors and three reference electrodes. The sweetness test was repeated 5 times for each sample solution, and the other taste tests were repeated 4 times. The average value of the last three data for each sample were taken as the test result. The potential values obtained from nine taste tests were converted into the final data throughthe analysis software of the electronic tongue. In the data analysis phase, we used multiple analysis packages from R language, including Factoextra, Cluster, FactoMineR, Ggplot2, Ggcorrplot and Ggrepel.【Results】By investigating the taste characteristics of 50 accessions of the Chinese plum germplasms, it was found that the plum varieties from different ecological origins exhibited some differences in taste characteristics but were not easy to distinguish overall. Conversely, there was a correlation between the flesh color and taste perception, the different flesh colors showed distinct distribution patterns in taste characteristics. The aftertaste- A exhibited a relatively scattered distribution in orange yellow flesh and yellow flesh, while a dispersed distribution of acidity, sweetness, and freshness in the red flesh. The faint yellow flesh was relatively concentrated in the taste sense of freshness and bitterness. The description of acidity/sweetness also reflected a certain relationship with the taste sense. The sourness exhibited a higher median value in the freshness taste parameter, while sweetness had a higher median value in the sweetness taste parameter. The high correlation between the sourness and sweetness suggested that these tastes could often coexist in certain plums. Based on the cluster analysis, the germplasms could be divided into six groups. There were analysis conducted in the second, the third, and the sixth groups, including the box diagram analysis and principal component analysis. In the umami, and sweetness, the distributions of the cluster 2, cluster 3 and cluster 6 were similar and discrete relatively, while the cluster 6 had higher values in the umami and sweetness than those of the other two groups. In PCA analysis, the cluster 2 was mainly distributed in the second quadrant, the cluster 3 was mainly distributed in the fourth quadrant, and the cluster 6 is mainly distributed in the second and third quadrant. At the same time, the taste specific germplasm resources were objectively screened. Sanhuali had the lowest sourness taste and the highest sweetness value, with outstanding umami value. On the contrary, Changlidazili showed the maximum value of sourness and the minimum value of sweetness in taste, while Qiuwangli, Zhengzhouzaoli, and Zhenzhuli had prominent saltness taste characteristics, while Hongbaoshi had the maximum bitterness taste characteristics and was accompanied by a large astringency taste value, Jinxiqiyueli also showed the highest value in bitterness and aftertaste-A, while Qingzhouli and Jinxipingdingxiangli showed a high degree of taste diversity.【Conclusion】The Chinese plums could be categorized into sour and astringent type, salty and tangy type, and fresh and sweet type. This study also identified a range of germplasm materials with outstanding taste attributes. These findings would provide a scientific basis for plum variety identification and classification, and are of significant importance for plum quality improvement.