The present study investigates the comparative effect of pre- and post-storage quarantine heat treatments (hot water treatment (HWT) and vapor heat treatment (VHT)) on the post-harvest performance of the mango fruit cv. ‘Chenab Gold’. The results indicate that the application of HWT at 48 °C for 60 min or VHT at 47 °C for 25 min after 21 days under cold storage enhanced the ethylene production and fruit weight loss, while decreasing fruit firmness and vitamin C content. Noticeably, the post-storage heat treatments ruptured the fruit and destroyed their market value. However, fruit treated with HWT or VHT at harvest exhibited slow weight loss, better skin color, and maintained biochemical attributes as compared to the control when kept under ambient storage conditions. Taken together, the application of hot water before storage has a positive influence on mango fruit quality, while post-storage heat treatment has a devastating impact upon fruit quality and shelf life, cancelling its potential commercial application.

Background: Leaves are the main organs involved in photosynthesis. They capture light energy and promote gas exchange, and their size and shape affect yield. Identifying the regulatory networks and key genes that control citrus leaf size is essential for increasing citrus crop yield. Methods: In this study, transcriptome sequencing was performed on three leaf materials: the ‘Cuimi’ kumquat (Nor) variety and its leaf variants, larger-leaf (VarB) and smaller-leaf (VarS) varieties. Results: Correlation and principal component analyses revealed a relatively close correlation between Nor and VarS. A total of 7264 differentially expressed genes (DEGs), including 2374 transcription factors (TFs), were identified, and 254 DEGs were common among the three materials. GO and KEGG enrichment analyses revealed significant enrichment in glucose metabolism, cell wall composition, starch biosynthesis, and photosynthesis pathways. WGCNA identified three specific modules related to the different leaf sizes of these three citrus materials. Fifteen candidate genes related to leaf size, including three transcription factors, Fh5g30470 (MYB), Fh7g07360 (AP2/ERF), and Fh5g02470 (SAP), were identified on the basis of connectivity and functional annotations. Conclusions: These findings provide a theoretical foundation for a deeper understanding of the molecular mechanisms underlying citrus leaf size and offer new genetic resources for the study of citrus leaf size.

To establish standardized DNA fingerprinting and molecular identification systems for mandarin citrus, we analyzed 69 mandarin accessions via fluorescent SSR capillary electrophoresis to construct DNA molecular fingerprints and unique molecular identity cards. Eighteen highly polymorphic SSR primer pairs were screened, yielding 239 genotype calls and 147 alleles. The number of amplified alleles per primer pair ranged from 4 to 18, with polymorphic information content (PIC) values varying from 0.411 to 0.650. Ten core primer pairs were further selected, achieving a discrimination rate of 65.2% (45 out of 69 accessions distinguished). Utilizing these fluorescent SSR markers, we established DNA molecular fingerprints and unique molecular identity cards for all 69 accessions. Among them, 45 accessions possessed unique fingerprints, whereas the remaining 24 indistinguishable accessions were clustered into six groups. Each cluster contained both wild (4 accessions total) and cultivated (20 accessions total) resources with high genetic similarity, which merits further investigation. This study provides a practical foundation for the authentication, conservation, and genetic relationship analysis of mandarin germplasm resources and establishes a technical framework for standardizing mandarin variety identification.

To establish standardized DNA fingerprinting and molecular identification systems for citrus, we analyzed 69 mandarin accessions via fluorescent SSR capillary electrophoresis to construct DNA molecular fingerprints and unique molecular identity cards. Eighteen highly polymorphic SSR primer pairs were screened, yielding 239 genotype calls and 147 alleles. The number of amplified alleles per primer pair ranged from 4 to 18, with polymorphic information content (PIC) values varying from 0.411 to 0.650. Ten core primer pairs were further selected, achieving a discrimination rate of 65.2% (45 out of 69 accessions distinguished). Utilizing these fluorescent SSR markers, we established DNA molecular fingerprints and unique molecular identity cards for all 69 accessions. Among them, 45 accessions possessed unique fingerprints, whereas the remaining 24 indistinguishable accessions were clustered into six groups. Each cluster contained both wild (4 accessions total) and cultivated (20 accessions total) resources with high genetic similarity, which merits further investigation. This study lays a theoretical basis for the authentication, conservation, and genetic relationship analysis of mandarin germplasm resources, and provides a practical tool for standardizing mandarin variety identification.

Low-temperature stored mandarin was prone to rapid quality deterioration when moved to a room-temperature shelf (RTS). However, systematic research on the safe threshold of time for low-temperature storage (LTS) and the key metabolic mechanisms underlying the quality deterioration was lacking. The dynamic changes in color, intrinsic quality, off-flavor and volatility of ‘Orah’ mandarin during LTS (6–8 °C, 0 d to 180 d) and thereafter RTS for 7 days were determined, and the key characteristic metabolites related to deterioration were analyzed. RTS after an LTS for 0 d, 20 d, 40 d, 60 d, 80 d, 100 d or 120 d exacerbated the decline in pericarp chromatic a* value, content of soluble solid, titratable acid, vitamin C, sucrose and malic acid in the pulp, as well as the accumulation of ethanol, methanol and acetaldehyde. After the LTS for 120 days and thereafter RTS for 7 days, the accumulation of ethanol exceeded 2000 mg/L, resulting in a distinct unpleasant odor. Seven categories (alcohols, aldehydes, esters, lipids/fatty acyls, terpenoids, organic acids, tetrahydropyrans) and 43 volatile substances were detected in the pulp. A significant decrease in terpenes within the first 60 days of LTS resulted in fast loss of aroma, while the substantial increase in ethanol, methanol and acetaldehyde (ethyl octoate, caproic acid) in the middle and later stages of LTS contributed to the prominent off-flavor. In conclusion, the LTS should not exceed 100 days due to the intensified accumulation of ethanol. The above results indicated that intervention techniques should be implemented to inhibit the synthesis of ethanol in the middle of storage, and methods such as reducing temperature fluctuations should be used to block the rapid accumulation of ester compounds during the RTS.