Perspectives on the adaptation of Japanese plum-type cultivars to reduced winter chilling in two regions of Spain.

Japanese plum, like other temperate fruit tree species, has cultivar-specific temperature requirements during dormancy for proper flowering. Knowing the temperature requirements of this species is of increasing interest due to the great genetic variability that exists among the available Japanese plum-type cultivars, since most of them are interspecific hybrids. The reduction of winter chilling caused by climate change is threatening their cultivation in many regions. In this work, the adaptation perspectives of 21 Japanese plum-type cultivars were analyzed in two of the main plum-growing regions in Spain, Badajoz and Zaragoza, to future climate conditions. Endodormancy release for subsequent estimation of chilling and heat requirements was determined through empirical experiments conducted during dormancy at least over two years. Chill requirements were calculated using three models [chilling hours (CH), chilling units (CU) and chilling portions (CP)] and heat requirements using growing degree hours (GDH). Chilling requirements ranged 277-851 CH, 412-1,030 CU and 26-51 CP, and heat requirements ranged from 4,343 to 9,525 GDH. The potential adaption of the cultivars to future warmer conditions in both regions was assessed using climate projections under two Representative Concentration Pathways (RCP), RCP4.5 (effective reduction of greenhouse gas emissions) and RCP8.5 (continuous increase in greenhouse gas emissions), in two time horizons, from the middle to the end of 21st century, with temperature projections from 15 Global Climate Models. The probability of satisfying the estimated cultivar-specific chilling requirements in Badajoz was lower than in Zaragoza, because of the lower chill availability predicted. In this region, the cultivars analyzed herein may have limited cultivation because the predicted reduction in winter chill may result in the chilling requirements not being successfully fulfilled.

Transcriptome Insights into Candidate Genes of the SWEET Family and Carotenoid Biosynthesis during Fruit Growth and Development in Prunus salicina 'Huangguan'.

The Chinese plum (Prunus salicina L.) is a fruit tree belonging to the Rosaceae family, native to south-eastern China and widely cultivated throughout the world. Fruit sugar metabolism and color change is an important physiological behavior that directly determines flavor and aroma. Our study analyzed six stages of fruit growth and development using RNA-seq, yielding a total of 14,973 DEGs, and further evaluation of key DEGs revealed a focus on sugar metabolism, flavonoid biosynthesis, carotenoid biosynthesis, and photosynthesis. Using GO and KEGG to enrich differential genes in the pathway, we selected 107 differential genes and obtained 49 significant differential genes related to glucose metabolism. The results of the correlation analyses indicated that two genes of the SWEET family, evm.TU.Chr1.3663 (PsSWEET9) and evm.TU.Chr4.676 (PsSWEET2), could be closely related to the composition of soluble sugars, which was also confirmed in the ethylene treatment experiments. In addition, analysis of the TOP 20 pathways between different growth stages and the green stage, as well as transient overexpression in chili, suggested that capsanthin/capsorubin synthase (PsCCS) of the carotenoid biosynthetic pathway contributed to the color change of plum fruit. These findings provide an insight into the molecular mechanisms involved in the ripening and color change of plum fruit.

Integrated Cytological, Physiological, and Transcriptome Analyses Provide Insight into the Albino Phenotype of Chinese Plum (Prunus salicina).

Albino seedlings that arise during seed reproduction can have a significant impact on plant growth and breeding. In this research, we present the first report of albino occurrences in the seed reproduction process of Prunus salicina and describe the cytological, physiological, and transcriptomic changes observed in albino seedlings. The albino seedlings which were observed in several plum cultivars exhibited abnormal chloroplast ultrastructure and perturbed stomatal structure. Compared to normal seedlings, the photosynthetic pigment contents in albino seedlings decreased by more than 90%, accompanied by significant reductions in several chlorophyll fluorescence parameters. Furthermore, substantially changed photosynthetic parameters indicated that the photosynthetic capacity and stomatal function were impaired in albino seedlings. Additionally, the activities of the antioxidant enzyme were drastically altered against the background of higher proline and lower ascorbic acid in leaves of albino seedlings. A total of 4048 differentially expressed genes (DEGs) were identified through transcriptomic sequencing, and the downregulated DEGs in albino seedlings were greatly enriched in the pathways for photosynthetic antenna proteins and flavonoid biosynthesis. GLK1 and Ftsz were identified as candidate genes responsible for the impaired chloroplast development and division in albino seedlings. Additionally, the substantial decline in the expression levels of examined photosystem-related chloroplast genes was validated in albino seedlings. Our findings shed light on the intricate physiological and molecular mechanisms driving albino plum seedling manifestation, which will contribute to improving the reproductive and breeding efforts of plums.

Potential mitigation of environmental impacts of intensive plum production in southeast China with maintenance of high yields: Evaluation using life cycle assessment.

Introduction: Intensive plum production usually involves high yields but also high environmental costs due to excessive fertilizer inputs. Quantitative analysis of the environmental effects of plum production is thereby required in the development of optimum strategies to promote sustainable fruit production. Methods: We collected survey questionnaires from 254 plum production farms in Zhao'an county, Fujian province, southeast China to assess the environmental impacts by life cycle assessment (LCA) methodology. The farms were categorized into four groups based on yield and environmental impacts, i.e., LL (low yield and low environmental impact), LH (low yield but high environmental impact), HL (high yield but low environmental impact), and HH (high yield and high environmental impact). Results: The environmental impacts, i.e., average energy depletion, global warming, acidification, and eutrophication potential in plum production were 18.17 GJ ha-1, 3.63 t CO2 eq ha-1, 42.18 kg SO2 eq ha-1, and 25.06 kg PO4 eq ha-1, respectively. Only 19.7% of farmers were in the HL group, with 13.3% in the HH group, 39.0% in LL, and 28.0% LH. Plum yields of the HL group were 109-114% higher than the mean value of all 254 farms. Additionally, the HL group had a lower environmental impact per unit area compared to the overall mean value, with a reduction ranging from 31.9% to 36.7%. Furthermore, on a per tonne of plum production basis, the energy depletion, global warming potential, acidification potential, and eutrophication potential of HL farms were lower by 75.4%, 75.0%, 75.6%, and 75.8%, respectively. Overall, the total environmental impact index of LL, LH, HL, and HH groups were 0.26, 0.42, 0.06, and 0.21, respectively. Discussion: Excessive fertilizer N application was the main source of the environmental impacts, the potential to reduce fertilizer N rate can be achieved without compromising plum yield by studying the HH group. The results provide an important foundation for enhancing the management of plum production, in order to promote 'green' agricultural development by reducing environmental impacts.

Corrigendum: Isolation, identification, biological characteristics, and antifungal efficacy of sodium bicarbonate combined with natamycin on Aspergillus niger from Shengzhou nane (Prunus salicina var. taoxingli) fruit.

[This corrects the article DOI: 10.3389/fmicb.2022.1075033.].

First report of rot disease in Prunus salicina var. taoxingli fruit caused by Fusarium lateritium in China.

Shengzhou nane (Prunus salicina var. taoxingli) as main cultivated plum in Zhejiang province, China, ripened in summer and was susceptible to microbial infection during the maturation stages because of high ambient temperature. In July 2022, Shengzhou nane fruits were found with symptoms of dark skin and grey-white lesions on surface, and an average incidence of approximate 16% (data obtained from investigation of ten trees in each orchard, and fifty fruits in each tree) in four orchards in Shengzhou city, Zhejiang province, China. To isolate the pathogen, four symptomatic partially rotted fruits (about 25%) from four orchards were collected. The plum tissue from the margin of lesions was excised into small blocks (4×4×3 mm). Eight blocks were disinfested with 70% ethanol for 30 seconds and 2% NaClO for 3 minutes, rinsed at least twice with distilled water, and incubated on PDA medium supplemented with 30.0 µg/mL Chloramphenicol at 25°C for 5 days in darkness until sporulation. Using single-spore isolation, four uniform isolates were obtained. The purified mycelium of isolates on PDA were milky white, the reverse on agar was dark pink. Colonies grew with a mean mycelium growth rate of 4.62 ± 0.38 mm per day on PDA. Macroconidia was shaped like a sickle and the size was 27.27 ± 3.43×4.54 ± 0.39 µm (n=50) with 2 to 3 septate. No microconidia and chlamydospores were observed. These morphological characteristics were consistent with previous descriptions of Fusarium lateritium (F. lateritium) species (Yun et al. 2013). Molecular identification was performed by sequencing nuclear ribosomal internal transcribed spacer region (ITS) gene with ITS1/ITS4 (White et al. 1990) and translation elongation factor-1α (TEF) with EF1-728F/EF1-986R (Carbone and Kohn. 1999). The representative sequences were submitted to Genbank (Accession Nos. OP315081 for the ITS and OP394153 for the TEF-1α). Blastn result indicated that ITS and TEF-1a sequences shared 99.28% and 100% similarity with two strains of F. lateritium (GenBank Accession Nos. MK311296.1 and JF740854.1). To fulfill Koch's postulates, the isolated F. lateritium (TXL-IT5) with a conidial suspension (1×106 spores per mL) was inoculated on ten fresh harvested healthy mature Shengzhou nane fruits (20 µL per fruits) after surface sterilization. The control fruits were inoculated with 20 µL distilled water. The experiment was repeated three times. Fruits were kept in a sealed plastic boxes at 25 °C with 90% relative humidity in dark. Four days after inoculation, all inoculated fruits were infected and appeared the same symptoms which were found in naturally infected fruits while those in the control group remained symptomless. The pathogen was re-isolated from symptomatic rotten fruits using above-mentioned method and was identified as F. lateritium based on morphological characteristics as well as ITS and TEF gene sequences. In addition, this pathogen was reported to infect Dalbergia tonkinensis in north Vietnam (Nhung et al. 2018), causing shoot dieback of Acer negundo in northeast Poland (Patejuk et al. 2022), and rot of Chinese cherry during postharvest storage (Wang et al. 2020). However, to the best of our knowledge, this is the first report of F. lateritium causing rot on Shenshou nane fruits. Our findings serve as a warning for scientists and growers who should pay attention to this disease and take effective control strategies to reduce epidemics of this disease in China and other regions.

S-Locus Genotyping in Japanese Plum by High Throughput Sequencing Using a Synthetic S-Loci Reference Sequence.

Self-incompatibility in Prunus species is governed by a single locus consisting of two highly multi-allelic and tightly linked genes, one coding for an F-box protein-i.e., SFB in Prunus- controlling the pollen specificity and one coding for an S-RNase gene controlling the pistil specificity. Genotyping the allelic combination in a fruit tree species is an essential procedure both for cross-based breeding and for establishing pollination requirements. Gel-based PCR techniques using primer pairs designed from conserved regions and spanning polymorphic intronic regions are traditionally used for this task. However, with the great advance of massive sequencing techniques and the lowering of sequencing costs, new genotyping-by-sequencing procedures are emerging. The alignment of resequenced individuals to reference genomes, commonly used for polymorphism detection, yields little or no coverage in the S-locus region due to high polymorphism between different alleles within the same species, and cannot be used for this purpose. Using the available sequences of Japanese plum S-loci concatenated in a rosary-like structure as synthetic reference sequence, we describe a procedure to accurately genotype resequenced individuals that allowed the analysis of the S-genotype in 88 Japanese plum cultivars, 74 of them are reported for the first time. In addition to unraveling two new S-alleles from published reference genomes, we identified at least two S-alleles in 74 cultivars. According to their S-allele composition, they were assigned to 22 incompatibility groups, including nine new incompatibility groups reported here for the first time (XXVII-XXXV).

Anti-Inflammatory Effects of Polyphenols from Plum (Prunus salicina Lindl) on RAW264.7 Macrophages Induced by Monosodium Urate and Potential Mechanisms.

Acute gouty arthritis is an acute inflammatory reaction caused by the deposition of monosodium urate (MSU) crystals in joints and surrounding soft tissues. Controlling inflammation is the key to preventing acute gouty arthritis. Anti-inflammatory activities and the possible molecular mechanisms of plum (Prunus salicina Lindl cv. "furong") polyphenols (PSLP) on RAW264.7 macrophage cells induced by monosodium urate were investigated. PPSF significantly inhibited the activity of inflammatory factors such as tumor necrosis factor-α (TNF-α), interleukin-1ß (IL-1ß), and interleukin-18 (IL-18). In addition, PPSF exhibited excellent activation of superoxide dismutase (SOD) activity and reduction of intracellular reactive oxygen species (ROS) and malondialdehyde (MDA) levels in RAW264.7 macrophages. The results of global screening of all transcripts by RNA-seq revealed 8585 differentially expressed genes between the PSLP-treated group and the MUS group. From GO analysis, PSLP could affect the occurrence and development of RAW264.7 macrophage inflammation through biological processes, such as organic substance metabolism, intracellular organelles, and binding function. The regulation mechanism of PSLP on MSU-induced RAW264.7 macrophage inflammation may be achieved through the HIF-1 signaling pathway, renal cell carcinoma, the ErbB signaling pathway, and the FoxO signaling pathway. Therefore, PSLP has great prospects in the prevention of gout and similar inflammatory diseases.

Identification of Candidate Genes Associated with Pulp Color by Transcriptomic Analysis of 'Huaxiu' Plum (Prunus salicina Lindl.) during Fruit-Ripening.

The plum (Prunus salicina Lindl.) is one of the traditional and economically important stone fruit trees in China. Anthocyanins are important pigments in plums. However, little is known about the molecular mechanisms underlying anthocyanin accumulation in plum fruits, which has hindered research on the molecular mechanism of its utilization. Our research shows that the chlorophyll content was gradually decreased and the contents of anthocyanin and flavonoid increased during the coloring process of the pulp in 'Huaxiu' plums (P. salicina). Then, the RNA-Seq technique was used to analyze the transcriptome of pulp color changes with three different stages (yellow, orange, and red) in the 'Huaxiu' plum (P. salicina). A total of 57,119 unigenes with a mean length of 953 bp were generated, and 61.6% of them were annotated to public databases. The Gene Ontology (GO) database assigned 21,438 unigenes with biological process, cellular components, and molecular function. In addition, 32,146 unigenes were clustered into 25 categories for functional classification by the COG database, and 7595 unigenes were mapped to 128 KEGG pathways by the KEGG pathway database. Of these, 1095 (YS-versus-OS), 4947 (YS-versus-RS), and 3414 (OS-versus-RS) genes were significantly expressed differentially between two coloration stages. The GO and KEGG pathway enrichment analysis revealed that 20 and 1 differentially expressed genes (DEG) are involved in flavonoid biosynthesis and anthocyanin biosynthesis, respectively. Finally, we mainly identified three structural genes as candidate genes. The transcriptome information in this study provide a basis for further studies of pulp colors in plum and contribute to our understanding of the molecular mechanisms underlying anthocyanin biosynthesis in pulp.

Pollen-Pistil Interaction in Response to Pollination Variants in Subtropical Japanese Plum (Prunus salicina Lindl.) Varieties.

The Japanese plum (Prunus salicina Lindl.) is a fruit tree globally cultivated in temperate regions of the world. Its floral biology and yield are affected by several factors, with issues related to self- and cross- (in) compatibility among varieties being emblematic of the whole Rosaceae family. The aim of this work was to elucidate the fruit set, dynamics of pollen tube growth in pistil, and yield and other fruiting attributes, in 'Satluj Purple' and 'Kala Amritsari', probably the most popular subtropical Japanese plum varieties in northern regions of India. Specifically, we examined the response of six different pollination variants, namely to self-pollination, open-pollination with the two cultivars located in adjacent rows, open-pollination with the two cultivars located in distant rows, manual cross-pollination, supplementary pollination, and floral bouquet. During the two years of the investigation, both plum cultivars showed good in vitro pollen germination (on average, above 50%) at different sucrose concentrations, with the highest values for the 'Satluj Purple' and for the 15% concentration. In vivo, the analysis of the pollen growth in the various sections of the style indicated the best performance when pistils of 'Satluj Purple' were pollinated by pollen grains of cv. 'Kala Amritsari'. Cross-pollination also registered faster growth of pollen tube in pistil with the lowest number of incompatible pollen tubes compared to open- and self-pollination. From the productive point of view, cross-pollination showed the most pronounced results among the different pollination variants, with the highest initial fruit set (36.6%) and yield (28.0 kg/tree), and the shorter fruit development in 'Satluj Purple' (fruit set and yield in self-pollinated 'Satluj Purple' trees were 3.3% and 2.0 kg/tree, respectively). Conversely, the use of 'Satluj Purple' pollen for 'Kala Amritsari' showed poor results. Finally, in our study, 'Kala Amritsari' showed self-compatibility. We conclude that the main cause of poor fruit set in 'Satluj Purple' is self-incompatibility. The relevant genotypic-specific effects revealed by the analysis of the various pollination treatments also highlighted the importance of interplanting to increase fruit set and yield for subtropical Japanese plum varieties.

First report of mume virus A infecting Prunus salicina worldwide and Prunus mume in Korea.

Mume virus A (MuVA) of the genus Capillovirus in the family Betaflexiviridae was first isolated from a Japanese apricot tree (Prunus mume) exhibiting symptoms of diffuse chlorotic spots (Marais et al. 2018). MuVA infection has been reported in Japanese apricot trees in Japan as well as in peach (P. persica) and Japanese apricot trees in China (Marais et al. 2018; Zhang et al. 2021; Zheng et al. 2020). In the present study, the diversity of viruses and viroids infecting Chinese plum trees (P. salicina) was investigated using high-throughput sequencing (HTS). Ten flowers each from 50 trees without obvious symptoms related to virus and/or viroid infection were randomly collected from five orchards in Gimcheon, Korea, in April 2020. The samples from each Chinese plum tree were pooled, and the same amounts of 50 individual samples prepared in advance were pooled for the extraction of total RNA using the RNeasy Plant Mini Kit (QIAGEN, Hilden, Germany). Removal of ribosomal RNA and construction of cDNA library from the extracted total RNA were conducted using the TruSeq Stranded Total RNA with Ribo-Zero Plant kit (Illumina, San Diego, CA, USA). Paired-end RNA sequencing using Illumina NovaSeq 6000 System (paired-end reads of 101 bp and a total of 162,845,322 reads) and data analysis were performed at Macrogen (Daejeon, Korea). Adaptor and low-quality sequences of reads were removed using Trimmomatic program. Trimmed reads were assembled into contigs using Trinity program, and several databases including NCBI Nucleotide and Kyoto Encyclopedia of Genes and Genomes were used for functional annotation. HTS identified plum bark necrosis stem pitting-associated virus (PBNSPaV; four contigs ranging from 2081 to 3202 nucleotides) and hop stunt viroid (HSVd; one contig of 618 nucleotides). PBNSPaV and HSVd were also detected by RT-PCR (PBNSPaV det-F and PBNSPaV det-R for PBNSPaV [Al Rwahnih et al. 2007]; VP-19 and VP-20 for HSVd [Astruc et al. 1996]) and confirmed by Sanger sequencing of the amplified products. Interestingly, one contig derived from MuVA, which was not previously reported in Korea, was also detected. The contig was 7,618-nucleotide long (15,205 reads), and NCBI BLASTN search revealed 98.74% homology (100% query coverage) with the MuVA isolate pm14 (GenBank accession number MG783575). To design diagnostic primers for reverse transcription (RT)-polymerase chain reaction (PCR), the contig sequence and MuVA sequences available in NCBI GenBank (GenBank accession numbers MG783575 and MN412555) were aligned using CLC Main Workbench 6.9.1 (QIAGEN, Redwood, CA, USA). The following primer set (expected size of 1,143 bp) was prepared: MuVA-2F (5'-CAGCTTTGTGACTCYAACCC-3') and MuVA-2R (5'-AATGGCTTGAGGRCCTGCAG-3'). The primers target a partial region (nt position 1185 to 2327 on the basis of the reference genome sequence of MuVA, GenBank accession no. NC_040568) of the polyprotein gene (ORF1). Each of the 50 samples was tested for the presence of MuVA using the above-mentioned RT-PCR primers with SuPrimeScript RT-PCR Premix (GeNet Bio, Daejeon, Korea). MuVA was detected in three samples collected from the same orchard. The three amplicons were inserted into a T&A cloning vector (RBC Bioscience, Taipei, Taiwan) and sequenced at Macrogen. Three consensus sequences obtained by Sanger sequencing were registered in NCBI GenBank under accession numbers MW589492, MW589493, and MW589494. NCBI BLASTN search revealed that the Korean isolates of MuVA shared high homology with isolate pm14 [98.16%, 98.08%, and 98.16% (100% query coverage), respectively]. To confirm additional MuVA infections, leaf samples of Chinese plum trees were collected from orchards in Uiseong (70 trees) and Seongju (50 trees) as well as a Japanese apricot tree in Chuncheon, from April to July 2021. RT-PCR confirmed additional MuVA infections from Uiseong (one tree) and Seongju (one tree) as well as from the Japanese apricot tree in Chuncheon. NCBI BLASTN search of the three additional amplicons (GenBank accession numbers OM210030, OM210031, and OM210032) revealed high homology with isolate pm14 [98.25%, 98.08%, and 97.90% (100% query coverage)]. To the best of our knowledge, this is the first report of MuVA infecting P. mume in Korea and P. salicina worldwide. Further research is needed to investigate MuVA infections on various Prunus spp. including P. persica in Korea.

Phenotypic Variation and Peel Contribution to Fruit Antioxidant Contents in European and Japanese Plums.

Herein, we studied the variation in leaf and fruit morphological traits and antioxidant contents in 43 local and foreign cultivars (cvs) grown under the same experimental conditions in the widely cultivated plum species Prunus domestica and Prunus salicina. The peel contribution of fruit bioactive compounds in a serving portion, correlations among the examined parameters, and group patterns in each plum species were also studied. The species and cvs were sufficiently separated. Compared to Japanese cvs, European cvs had less elongated leaves and smaller and sweeter fruit with less total phenol and antioxidant capacities. The Japanese cvs 'Red ace' and the widely grown 'Black Amber', together with the European 'Tuleu Dulce', 'BlueFre', and the landrace 'Asvestochoriou' make up groups with rich dietary sources of phytochemicals. The peel tissue contained higher total phenols and antioxidant capacities compared to the flesh, while the peel/flesh ratios varied widely among the cvs (6.6-fold). The variation in the antioxidant contents was lower among the cvs calculated per serving portion (3.7-fold); yet the peel tissue contribution was equal to that of the flesh (48.6%), signifying its high nutritive value. We observed increased sweetness in the fruit in the later-harvested cultivars, while cvs with more blue- and red-colored peel generally contained higher antioxidant contents mainly in the European plums. Moreover, larger fruit sizes were positively correlated with larger and more elliptic leaf shapes. In conclusion, the significant role of the genotype and the peel tissue as a source of bioactive compounds in plums were outlined with prospects of utilization in future breeding programs.

Japanese plums behavior under water stress: impact on yield and biochemical traits.

This work investigates response to drought of nine local cultivars alongside two exotic varieties of Japanese plum (Prunus salicina L.) through their yield and fruit quality components. It was carried out at Sais plain, northern Morocco, over two consecutive years (2019-2020). Water stress was imposed by a deficit irrigation (DI) treatment of 50% ETc during the whole fruit growth period, compared to full irrigation of 100% ETc (CI). At their full ripening stage, the cultivars were assessed for their yield, fruit weight and fruit quality attributes, namely total soluble solids (TSS), pH, titratable acidity (TA), maturity index (MI), soluble sugars content (SSC), amino acids content (AAC), total phenolic compounds (TPC) and total antioxidant capacity (TAC). Results displayed significant decrease in yield and fruit weight since the first year of DI application. Owing to calculated stability indexes of the aforementioned traits along with water use efficiency, the local cultivar 'Fortu-43' was the most insensitive to drought, whereas 'Timhdit' and 'Black-D35' showed the lowest drought tolerability. The effects of water stress on fruit chemical and biochemical traits varied significantly among cultivars, exhibiting an overall significant improvement in fruit quality. Two-dimensional clustered heatmap analysis subdivided the cultivars into two distinct clusters, mainly discriminated based on stability indexes of SSC, MI, TPC and TAC. Among the latter, SSC stability index was probably the most significant drought tolerance marker for Japanese plum.

Isolation, Characterization, Antioxidant Activity, Metal-Chelating Activity, and Protein-Precipitating Capacity of Condensed Tannins from Plum (Prunus salicina) Fruit.

The type of polymeric condensed tannins from plum fruit (Prunus salicina) (PCT), the degree of polymerization and the distribution of polymers were characterized by MALDI-TOF MS and NMR spectroscopy. The metal-binding capacity of PCT with five metal ions (Cu2+, Zn2+, Al3+, Fe2+, and Fe3+) was characterized by a fluorescence quenching method. The results demonstrated the following: epicatechin was the basic unit occurring in PCT, and A-type and B-type linkages were the most common between the structural units of the polymers. The PCT have a strong antioxidant activity, which is comparable with that of the synthetic antioxidant BHA. The quenching mechanism of the PCT's fluorescence intensity by Zn2+, Cu2+, and Al3+ was different from that of Fe3+ and Fe2+. Fe3+, Al3+ and Fe2+ had much higher affinities for the PCT than Zn2+ and Cu2+. A simple UV-Vis spectra method was developed to determine the protein-precipitating capacity of tannins. Bovine serum albumin (BSA) was effectively precipitated by tannins isolated from plum fruits, Chinese gallnut, sorghum grain, and Platycarya strobilacea at pH values between 4.5 and 5.0. A statistically significant linear relationship (p < 0.0001 or p < 0.0003) existed between the amount of tannin−protein complex formed and the amount of tannins added to the reaction mixture. The slopes of these lines indicated the protein-precipitating capacity of tannins.

Cancer protective effects of plums: A systematic review.

Plums is one of the most cultivated stone fruits due to its fast growing popularity. It has various traditionally recognized health benefits. There are two main commercial types of plums: the European plum (Prunus domestica) and the Japanese plum (Prunus salicina), each having many varieties. Researchers are gathering further evidence of pharmacological effects for plums by scientifically studying its anti-inflammatory, antioxidant properties. A systematic review analysing the literature related to the effects of plums on prevention and treatment of cancer is warranted. This is the first review examining the cancer-related effects of plums. Antioxidation properties of the active constituents of plum were also compared. Scopus, Google Scholar, PubMed, Medxriv and Cochrane Library databases, from their date of inception until July 2021 were utilized. The risk of bias was assessed using CONSORT checklist. A total of 6639 studies were screened and eventually only 54 studies were included. Full-text review of included studies revealed that plum extracts were rich in antioxidants. Overall, most of the studies that fulfilled the eligibility criteria were in vitro and a few clinical studies involving in vivo work. Therefore, it would be beneficial to perform more studies on animals or humans, to confirm that the result obtained from these in vitro studies are able to be extrapolated in a wider range of applications. Further clinical and in vivo studies are warranted to validate plums as a functional food for treatment and prevention of cancer.

Isolation, identification, biological characteristics, and antifungal efficacy of sodium bicarbonate combined with natamycin on Aspergillus niger from Shengzhou nane (Prunus salicina var. taoxingli) fruit.

The fungi causing fruit rot were isolated from symptomatic Shengzhou nane (Prunus salicina var. taoxingli) fruit and were identified as Aspergillus niger by biological characteristics and molecular analysis of the internal transcribed spacer region (rDNA-ITS) and translation elongation factor-1α (TEF-1α) sequences. Optimal growth conditions for A. niger were 30°C, pH 5.0-6.0, and fructose and peptone as carbon and nitrogen sources. The effects of sodium bicarbonate (SBC), natamycin (NT), and combined treatments on A. niger inhibition were investigated. Treatment with 4.0 g/L sodium bicarbonate (SBC) + 5.0 mg/L natamycin (NT) inhibited mycelial growth and spore germination as completely as 12.0 mg/L SBC or 25.0 mg/L NT. SBC and NT treatments disrupted the structural integrity of cell and mitochondria membranes and decreased enzyme activities involved in the tricarboxylic acid (TCA) cycle, mitochondrial membrane potential (MMP), ATP production in mitochondria, and ergosterol content in the plasma membrane, thus leading to the inhibition of A. niger growth. Moreover, experimental results in vivo showed that the rot lesion diameter and decay rate of Shengzhou nane fruit treated with SBC and NT were significantly reduced compared with the control. The results suggest that the combination treatment of SBC and NT could be an alternative to synthetic fungicides for controlling postharvest Shengzhou nane decay caused by A. niger.

Biostimulants promote the accumulation of carbohydrates and biosynthesis of anthocyanins in 'Yinhongli' plum.

Biostimulants play an important role in promoting crop growth and development and improving fruit yield, but their influence on fruit quality in horticulture plants is still unclear. In this study, four types of biostimulants, Ainuo (AN), Aigefu (AG), Weiguo (WG), and Guanwu Shuang (GS) were applied to the fruit surface of 'Yinhongli' plum at 60 and 75 days after anthesis to investigate their effect on carbohydrates and biosynthesis of anthocyanins, and also analyze the relationship between sugar and anthocyanin accumulation during fruit color change to ripening. Results showed that all biostimulant treatments significantly improved fruit appearance quality, and increased single fruit weight and TSS/TA. Cyanidin 3-O-glucoside and cyanidin 3-O-rutinoside, are the most important anthocyanins in the red skin of the 'Yinhongli' plum, and no anthocyanin was detected in the green skin. In addition, WG and GS treatments significantly increased the expression of structural genes involved in anthocyanin biosynthesis compared with the control, especially chalcone synthase (CHS) and flavonoid 3-O-glucosyltransferase (UFGT) at 95-105 d after anthesis, leading to anthocyanin accumulation 10 days earlier than the control. Correlation analysis showed that there was a significant correlation between total sugar and anthocyanin content during fruit coloring and ripening.

Assembly of the Complete Mitochondrial Genome of Chinese Plum (Prunus salicina): Characterization of Genome Recombination and RNA Editing Sites.

Despite the significant progress that has been made in the genome sequencing of Prunus, this area of research has been lacking a systematic description of the mitochondrial genome of this genus for a long time. In this study, we assembled the mitochondrial genome of the Chinese plum (Prunus salicina) using Illumina and Oxford Nanopore sequencing data. The mitochondrial genome size of P. salicina was found to be 508,035 base pair (bp), which is the largest reported in the Rosaceae family to date, and P. salicina was shown to be 63,453 bp longer than sweet cherry (P. avium). The P. salicina mitochondrial genome contained 37 protein-coding genes (PCGs), 3 ribosomal RNA (rRNA) genes, and 16 transfer RNA (tRNA) genes. Two plastid-derived tRNA were identified. We also found two short repeats that captured the nad3 and nad6 genes and resulted in two copies. In addition, nine pairs of repeat sequences were identified as being involved in the mediation of genome recombination. This is crucial for the formation of subgenomic configurations. To characterize RNA editing sites, transcriptome data were used, and we identified 480 RNA editing sites in protein-coding sequences. Among them, the initiation codon of the nad1 gene confirmed that an RNA editing event occurred, and the genomic encoded ACG was edited as AUG in the transcript. Combined with previous reports on the chloroplast genome, our data complemented our understanding of the last part of the organelle genome of plum, which will facilitate our understanding of the evolution of organelle genomes.

Silverleaf (Chondrostereum purpureum) Effects on Japanese Plum (Prunus salicina).

Silverleaf is an important fungal trunk disease of fruit crops, such as Japanese plum (Prunus salicina). It is known that infection by Chondrostereum purpureum results in discolored wood, "silvered" foliage, and tree decline. However, effects on fruit yield and quality have not been assessed. Therefore, the objectives of this study were to determine C. purpureum pathogenicity on P. salicina and the effects on physiology, fruit yield, and quality, in Chile, in 2019 and 2020. Wood samples from affected plum trees were collected in the Chilean plum productive area. Fungi were isolated by plating wood sections from the necrosis margin on culture media. Morphological and molecular characteristics of the isolates corresponded to C. purpureum (98%). Representative isolates were inoculated from healthy plum plants and after 65-d incubation, wood necrotic lesions and silver leaves were visible. Fungi were reisolated, fulfilling Koch's postulates. To determine Silverleaf effects, xylem water potential and fruit yield and quality were measured in healthy and Silverleaf-diseased plum trees 'Angeleno'. Water potential was altered in diseased trees, and fruit yield was reduced by 51% (2019) and by 41% (2020) compared to fruit from healthy trees. Moreover, cover-colour, equatorial-diameter, and weight were reduced, and fruit were softer, failing to meet the criteria to be properly commercialized and exported to demanding markets.

Chromosome-scale genome assembly and population genomics provide insights into the adaptation, domestication, and flavonoid metabolism of Chinese plum.

Globally, commercialized plum cultivars are mostly diploid Chinese plums (Prunus salicina Lindl.), also known as Japanese plums, and are one of the most abundant and variable fruit tree species. To advance Prunus genomic research, we present a chromosome-scale P. salicina genome assembly, constructed using an integrated strategy that combines Illumina, Oxford Nanopore, and high-throughput chromosome conformation capture (Hi-C) sequencing. The high-quality genome assembly consists of a 318.6-Mb sequence (contig N50 length of 2.3 Mb) with eight pseudo-chromosomes. The expansion of the P. salicina genome is led by recent segmental duplications and a long terminal repeat burst of approximately 0.2 Mya. This resulted in a significant expansion of gene families associated with flavonoid metabolism and plant resistance, which impacted fruit flavor and increased species adaptability. Population structure and domestication history suggest that Chinese plum may have originated from South China and provides a domestication route with accompanying genomic variations. Selection sweep and genetic diversity analysis enabled the identification of several critical genes associated with flowering time, stress tolerance, and flavonoid metabolism, demonstrating the essential roles of related pathways during domestication. Furthermore, we reconstructed and exploited flavonoid-anthocyanin metabolism using multi-omics analysis in Chinese plum and proposed a complete metabolic pathway. Collectively, our results will facilitate further candidate gene discovery for important agronomic traits in Chinese plum and provide insights into future functional genomic studies and DNA-informed breeding.