Molecular Insights of Fruit Quality Traits in Peaches, Prunus persica

Combined Metabolome and Transcriptome Analyses Unveil the Molecular Mechanisms of Fruit Acidity Variation in Litchi (Litchi chinensis Sonn.)

Fruit acidity determines the organoleptic quality and nutritive value of most fruits. In litchi, although the organic acid composition of pulps is known, the molecular mechanisms and genes underlying variation in fruit acidity remain elusive. Herein, developing pulps of two contrasting litchi varieties, Huaizhi (HZ, low-acidity) and Boye_No.8 (B8, high-acidity), were subjected to metabolomics and transcriptomics, and the dynamic metabolome and transcriptional changes were determined. Measurements revealed that the dominant acidity-related organic acid in litchi pulps is malate, followed in low levels by citrate and tartrate. Variation in litchi pulps' acidity is mainly associated with significant differences in malate and citrate metabolisms during fruit development. Malic acid content decreased by 91.43% and 72.28% during fruit ripening in HZ and B8, respectively. The content of citric acid increased significantly in B8, while in HZ it was reduced considerably. Differentially accumulated metabolites and differentially expressed genes analyses unveiled fumarate, succinate, 2-oxoglutarate, GABA (γ-aminobutyric acid), phosphoenolpyruvate, and citrate metabolisms as the key driving pathways of litchi fruits' acidity variation. The drastic malate and citrate degradation in HZ was linked to higher induction of fumarate and GABA biosynthesis, respectively. Thirty candidate genes, including three key genes (LITCHI026501.m2, fumarase; LITCHI020148.m5, glutamate decarboxylase; and LITCHI003343.m3, glutamate dehydrogenase), were identified for functional studies toward genetic modulation of litchi fruit acidity. Our findings provide insights into the molecular basis of acidity variation in litchi and provide valuable resources for fruit quality improvement.

Transcriptomic and Metabolomic Analysis of Quality Changes during Sweet Cherry Fruit Development and Mining of Related Genes

Sweet cherries are economically important fruit trees, and their quality changes during development need to be determined. The mechanism of fruit quality changes in sweet cherries were determined by analyzing sweet cherry fruits at 12 developmental stages. The results showed that the soluble sugar, anthocyanin content, and hormones of sweet cherries all changed drastically during the color transition. Therefore, the fruits at the beginning of color conversion, at the end of color conversion, and at the ripening state were selected for the comprehensive analysis of their metabolome and transcriptome. Different sugars, such as D-glucose, sucrose, and trehalose, were identified in the metabolome. Dihydroquercetin, delphinidin-3-glucoside, cyanidin-3-rutincoside, and other flavonoid species were also identified. D-glucose and cyanidin-3-rutinoside were among the most important components of sweet cherry soluble sugars and anthocyanins, respectively. The transcriptional analysis identified key structural genes and nine transcription factors involved in the ABA, sugar, organic acid, and anthocyanin synthesis pathways, with the following specific regulatory patterns. NAC71, WRKY57, and WRKY3 regulate fruit sugar accumulation mainly by acting on INV, SPS, and SUS. MYC2 is involved in the synthesis of anthocyanin precursors by activating PAL and C4H, whereas TCP7 mainly regulates CHI and F3H. WRKY3, NAC71, and WRKY57 have important positive regulatory significance on anthocyanin accumulation, mainly by activating the expression of DFR, ANS, and 3GT.

Addition of Combinedly Dehydrated Peach to the Cookies-Technological Quality Testing and Optimization

Peach dehydrated by a combined method of osmodehydration and lyophilization is characterized by upgraded dehydration effectiveness and enhanced chemical and mineral matter content, and as such, is an interesting material to be applied to the cookies’ formulation. Incorporation of this material requires testing and optimization of the addition level from the aspect of overall technological quality in order to obtain a new cookie product. Obtained cookie samples with different levels of dehydrated peach addition were subjected to the nutritive and technology quality parameters testing. Cookies’ chemical, mineral matter, and phenolic compounds content, the antioxidative activity of nutritive parameters, and the physical, technological, textural, colour, and sensory characteristics of technological parameters were investigated. Obtained results showed that the addition of especially higher levels of dehydrated peach enhanced all nutritive, while simultaneously decreased most of the technological quality parameters. The statistical method of Z-score analysis was used to calculate the optimal level of dehydrated peach addition to the cookie formulation for obtaining the highest nutritive enrichment without excessive technological quality deterioration. The optimal addition of osmodehydrated and lyophilized peach to the cookie formulation was determined to be 15%.

Evaluation of Nutritional Content in Wild Apricot Fruits for Sustainable Apricot Production

Apricot (Prunus armeniaca L.) trees are common from Asia to North America and have been used for delicious and nutritious fruits for centuries. Wild apricot trees show great environment plasticity and are free of pest and disease traits, both of which are important for sustainable apricot production. However, wild apricots are more common in Asia and North African countries. Wild apricot trees and fruits show great variability due to seed propagation characteristics. Seeds of wild apricots are used as rootstocks for apricot cultivars, in particular in main apricot producer countries such as Turkey, Uzbekistan, and Iran. Fruits of wild apricots are also an important food in wild apricot growing countries and add value as a sustainable nutrition source. In the present study, a total of 14 wild apricots widely grown in inner Anatolia were characterized by morphological (fruit weight, flesh/seed ratio, fruit firmness, and color index), nutritional (individual sugars and organic acids) and nutraceutical (total phenolic, total flavonoids, total carotenoid, and antioxidant activity) features. The obtained results showed that wild apricot genotypes differed from each other for most of the morphological, nutritional, and nutraceutical characteristics. The genotypes were found pest- and disease-free and had fruit weight, flesh/seed ratio, and fruit firmness of between 18.24 and 27.54 g; 8.96 and 12.44; and 4.05 and 6.03 kg/cm2, respectively. Citric acid was the dominant organic acid for fruits of all wild apricot genotypes, and ranged from 923 to 1224 mg/100 g. Sucrose was the highest soluble sugar in fruits for all wild apricots, and ranged from between 6.80 and 8.33 g/100 g. Moreover, the level of nutraceutical parameters also varied among genotypes and high amounts of total phenol and antioxidant activity were obtained in fruit extracts of IA8 genotype as 81.4 mg gallic acid equivalent per 100 g and 2.44 μmoL trolox equivalent per g, respectively. Different wild apricot genotypes are rich in certain nutritional and nutraceutical compounds, with significant variations in their levels being observed. The aim of the study was to evaluate fruits of wild apricot genotypes in terms of their total phenolics, antioxidants, and other bioactive compounds for use in future breeding programs and sustainable food and pharma industries.