Metabolome, Plant Hormone, and Transcriptome Analyses Reveal the Mechanism of Spatial Accumulation Pattern of Anthocyanins in Peach Flesh.

Anthocyanins are important secondary metabolites in fruits, and anthocyanin accumulation in the flesh of peach exhibits a spatial pattern, but the relevant mechanism is still unknown. In this study, the yellow-fleshed peach, cv. 'Jinxiu', with anthocyanin accumulation in the mesocarp around the stone was used as the experimental material. Red flesh (RF) and yellow flesh (YF) were sampled separately for flavonoid metabolite (mainly anthocyanins), plant hormone, and transcriptome analyses. The results showed that the red coloration in the mesocarp was due to the accumulation of cyanidin-3-O-glucoside, with an up-regulation of anthocyanin biosynthetic genes (F3H, F3'H, DFR, and ANS), transportation gene GST, and regulatory genes (MYB10.1 and bHLH3). Eleven ERFs, nine WRKYs, and eight NACs were also defined as the candidate regulators of anthocyanin biosynthesis in peach via RNA-seq. Auxin, cytokinin, abscisic acid (ABA), salicylic acid (SA), and 1-aminocyclopropane-1-carboxylic acid (ACC, ethylene precursor) were enriched in the peach flesh, with auxin, cytokinin, ACC, and SA being highly accumulated in the RF, but ABA was mainly distributed in the YF. The activators and repressors in the auxin and cytokinin signaling transduction pathways were mostly up-regulated and down-regulated, respectively. Our results provide new insights into the regulation of spatial accumulation pattern of anthocyanins in peach flesh.

Effect of ozonated water, mancozeb, and thiophanate-methyl on the phyllosphere microbial diversity of strawberry.

Phyllosphere microorganisms are closely linked to plant health. This study investigated the effect of ozonated water, mancozeb, and thiophanate-methyl on phyllosphere microorganisms in strawberry plants of the "Hongyan" variety. Sequencing analysis of the phyllosphere bacterial and fungal communities was performed using 16S rRNA gene fragment and ITS1 region high-throughput sequencing after spraying ozonated water, mancozeb, thiophanate-methyl, and clear water. Proteobacteria, Actinobacteria, and Firmicutes were the dominant bacterial phyla in strawberry. The relative abundance of Proteobacteria (82.71%) was higher in the ozonated water treatment group than in the other treatment groups, while the relative abundance of Actinobacteria (9.38%) was lower than in the other treatment groups. The strawberry phyllosphere fungal communities were mainly found in the phyla Basidiomycota and Ascomycota. The relative abundance of Basidiomycota was highest in the ozonated water treatment group (81.13%), followed by the mancozeb treatment group (76.01%), while the CK group only had an abundance of 43.38%. The relative abundance of Ascomycota was lowest in the ozonated water treatment group (17.98%), 23.12% in the mancozeb treatment group, 43.39% in the thiophanate-methyl treatment group, and 55.47% in the CK group. Pseudomonas, Halomonas, and Nesterenkonia were the dominant bacterial genera on strawberry surfaces, while Moesziomyces, Aspergillus, and Dirkmeia were the dominant fungal genera. Ozonated water was able to significantly increase the richness of bacteria and fungi and decrease fungal diversity. However, bacterial diversity was not significantly altered. Ozonated water effectively reduced the relative abundance of harmful fungi, such as Aspergillus, and Penicillium, and enriched beneficial bacteria, such as Pseudomonas and Actinomycetospora, more effectively than mancozeb and thiophanate-methyl. The results of the study show that ozonated water has potential as a biocide and may be able to replace traditional agents in the future to reduce environmental pollution.

Characterization of volatile constituents and odorous compounds in peach (Prunus persica L) fruits of different varieties by gas chromatography-ion mobility spectrometry, gas chromatography-mass spectrometry, and relative odor activity value.

The aim of this study is to acquire information for future breeding efforts aimed at improving fruit quality via effects on aroma by comparing the diversity of Chinese local peach cultivars across 10 samples of three varieties (honey peach, yellow peach, and flat peach). The volatile components of peach fruits were analyzed and identified by gas chromatography-ion mobility spectrometry (GC-IMS) combined with gas chromatography-mass spectrometry (GC-MS), and the main flavor components of peach fruit were determined by relative odor activity value (ROAV) and principal component analysis (PCA). A total number of 57 volatile components were detected by GC-IMS, including eight aldehydes, nine alcohols, eight ketones, 22 esters, two acids, two phenols, two pyrazines, one thiophene, one benzene, and two furans. The proportion of esters was up to 38.6%. A total of 88 volatile components were detected by GC-MS, among which 40 were key aroma compounds, with an ROAV ≥ 1. The analysis results showed that alcohols, ketones, esters, and aldehydes contributed the most to the aroma of peach fruit. PCA demonstrated that (E,E)-2, 6-non-adienal, γ-decalactone, ß-ionone, and hexyl hexanoate were the key contributors to the fruit aroma. A reference for future directional cultivation and breeding could be provided by this study through evaluating the aroma quality of the peach at the cultivar level. The possible reasonable application of these peach fruits pulp will be guided through these research.

Community Structure of Phyllosphere Bacteria in Different Cultivars of Fingered Citron (Citrus medica 'Fingered') and Their Correlations With Fragrance.

In recent years, plant metabolomics and microbiome studies have suggested that the synthesis and secretion of plant secondary metabolites are affected by microbial-host symbiotic interactions. In this study, six varieties of fingered citron (Citrus medica 'Fingered') are sampled to study their phyllosphere bacterial communities and volatile organic compounds (VOCs). High-throughput sequencing is used to sequence the V5-V7 region of the 16S rRNA of the fingered citron phyllosphere bacteria, and the results showed that Proteobacteria, Actinobacteria, Firmicutes, and Bacteroidetes were the dominant bacterial phylum in the phyllosphere of fingered citron. There were significant differences in the phyllosphere bacteria community between XiuZhen and the remaining five varieties. The relative abundance of Actinomycetospora was highest in XiuZhen, and Halomonas, Methylobacterium, Nocardioides, and Pseudokineococcus were also dominant. Among the remaining varieties, Halomonas was the genus with the highest relative abundance, while the relative abundances of all the other genera were low. Headspace solid-phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS) were used to analyze and identify the aroma compounds of six different fingered citron, and a total of 76 aroma compounds were detected in six varieties. Pinene, geraniol, and linalool were found to be the primary VOCs that affect the aroma of fingered citron based on relative odor activity value. The correlation analysis showed 55 positive and 60 negative correlations between the phyllosphere bacterial flora and aroma compounds of fingered citron. The top 10 genera in the relative abundance were all significantly associated with aroma compounds. This study provides deep insight into the relation between bacteria and VOCs of fingered citron, and this may better explain the complexity of the analysis of bacterial and metabolic interactions.