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Background The discovery of a plum tree isolate of plum pox virus (PPV, Potyvirus plumpoxi ), done in Eastern Albania in 2011 in the frame of an EU-funded survey, which represents a divergent strain named PPV-An, proved to be original and informative for the unraveling of PPV evolutionary history. Methods Maximum likelihood and Bayesian phylogenetic methods applied on full-length genomes or selected regions analyzed the affinities of the PPV-An with other PPV strains. Potential recombination events were also evaluated. A refined timeline of PPV evolutionary history integrating recombination events, strains migration and ancestral host state is proposed. Results Altogether, the analyses confirm previous hypotheses that PPV-An corresponds to an ancestral, non-recombinant PPV strain. PPV-An likely served as the origin of the PPV-M and T strains through recombination with isolate(s) of the D strain. Molecular clock analyses dated the most recent common ancestor (TMRCA) of PPV at 4546 years ago and phylogeny separated the main PPV strains from the cherry-adapted strains around 3100 years ago. Meanwhile, the recombination events that gave rise to the M and T strains are estimated to have occurred in the early sixteenth century of the common era (CE). Conclusions The characterization of the PPV-An strain enabled a comprehensive phylogenetic analysis of PPV. PPV-An is confirmed to be the previously unidentified progenitor, which, together with PPV-D led through recombination to the emergence of the currently prevalent and evolutionary successful recombinant strains of European origin (e.g., M, Rec, and T). The low representation of PPV-An in current PPV populations is likely the consequence of a population replacement phenomenon possibly linked to a higher fitness of the recombinant strains deriving from it. These results highlight the PPV-An strain as a key player in PPV evolutionary history and consolidate PPV as one of the promising models to study host-adaptive evolution processes and phylogeography among the most damaging viruses of agricultural systems.

Sharka, caused by plum pox virus (PPV), is by far the most harmful disease of stone fruits (genus Prunus). Although Italy is a major producer of stone fruits, and sharka has spread in most Italian regions since its first identification in the 1970s, information on the diffusion of the disease in Italy results still scattered and incomplete. To address this knowledge gap, the present review aimed to firstly provide a historical overview of sharka in Italy, summarizing outcomes on the disease achieved since the first identification of its causal agent PPV. Data retrieved from a variety of sources (i.e., published literature, official reports and personal communications) showed that (i) sharka spread across almost the whole Italian peninsula as only Liguria, Umbria and Aosta Valley regions officially result disease-free; (ii) the regions with higher rates of infected districts are not always those more dedicated to the production of stone fruits; (iii) only the three major PPV strains causing sharka, i.e., PPV-Dideron (D), PPV-Marcus (M), and PPV-Recombinant (Rec), have been reported in Italy; and (iv) only apricot, peach and plum (i.e., widespread and economically relevant species) are hosts of PPV, with different scenarios among regions. A focus on Tuscany (Central Italy) showed that, (i) sharka has been reported since the 1990s, but extensive PPV monitoring campaigns were run from 2013 to 2021, especially in nurseries; (ii) higher number of symptomatic and PPV positive samples were recorded in farms, mostly in the Arezzo and Florence districts; and (iii) only PPV-M and PPV-Rec strains seem still present. We believe that the present overview will benefit and encourage both researchers for future investigations on sharka and farmers that have to manage the disease.

Recent studies proposed that the negative strands of some single‐stranded, positive‐sense RNA viruses contain reverse open reading frames (rORFs) that encode functional peptides. Highly conserved rORFs were found in the negative strand of viruses within the Potyviridae family, including turnip mosaic virus (TuMV), where rORF2 was shown to be essential for infection and survival. In this study, we analysed the existence and potential functionality of rORFs in plum pox virus (PPV) using mass spectrometry and mutagenesis. Unbiased mass spectrometry analyses failed to identify any rORF‐encoded peptides and PPV mutants abolishing the expression of individual rORF‐derived peptides showed no significant difference in infection rates compared to the wild‐type virus in the experimental host Nicotiana benthamiana or in the natural host Prunus persica. Furthermore, competitive infection experiments revealed that neither the wild type nor the rORF2 knockout mutant, which had proven lethal when tested in TuMV, exhibited any competitive advantage over the other. Taken together, these findings suggest that rORFs in PPV are either not produced or are functionally irrelevant for infection, and they highlight the need to evaluate the role of rORFs in other potyviruses on a case‐by‐case basis. Plum pox virus produces two polyproteins from ORFs in the positive strand. This study explores the possible expression of peptides from negative‐strand ORFs (rORFs).

Plums are the predominant fruit crop in Serbia. In the period under consideration (2012–2021), the Serbian plum area accounted for, on average, 42.52 % of the total fruit area in the country, far surpassing all other fruit crops. The Republic of Serbia is one of the leading plum producers in the world. With an average annual plum production of 440.91 thousand tons, Serbia ranks third in the world (following only China and Romania), contributing 3.77% to the world’s total plum production. Nevertheless, the country faces challenges such as low yields per unit area, approximately 5.35 t/ha (FAO, 2023). Presently, the economic significance of plum production is not as high as in previous decades, and cultivation potential remains underutilized. To revitalize plum production in Serbia and reclaim its historical prominence, it is imperative to assess the current state of plum production both globally and regionally and implement appropriate measures to enhance economic performance in this traditional fruit sector.

Stone fruit trees of genus Prunus, like other temperate woody species, need to accumulate a cultivar-specific amount of chilling during endodormancy, and of heat during ecodormancy to flower properly in spring. Knowing the requirements of a cultivar can be critical in determining if it can be adapted to a particular area. Growers can use this information to anticipate the future performance of their orchards and the adaptation of new cultivars to their region. In this work, the available information on chilling- and heat-requirements of almond, apricot, plum, peach, and sweet cherry cultivars is reviewed. We pay special attention to the method used for the determination of breaking dormancy, the method used to quantify chilling and heat temperatures, and the place where experiments were conducted. The results reveal different gaps in the information available, both in the lack of information of cultivars with unknown requirements and in the methodologies used. The main emerging challenges are the standardization of the conditions of each methodology and the search for biological markers for dormancy. These will help to deal with the growing number of new cultivars and the reduction of winter cold in many areas due to global warming.

The amount of fruits and vegetables produced in Uzbekistan not only meets the demands of the republic's citizens, but also exports its high-quality goods to other countries. The work displays the findings of the thermogravimetric examination and computation of the kinetic parameters of fruits (apricots and plums) and vegetables (carrots and potatoes). When studying the kinetics of the process, the Wahuski-Voboril and Erofeev models were used, and a calculation program was given. For the first period, corresponding to the stage of drying fruits and vegetables, the best accuracy of 7.8% is given by the Wahuski-Voboril model. For the second and subsequent periods of the thermal decomposition process, the Erofeev model gives the largest error of 5.9.

Headspace gas chromatography–ion mobility spectrometry and partial-least-squares discriminant analysis (PLS-DA) were adopted to analyze the rule of change in flavor substances for different varieties of green plums at different levels of maturity (S1—immature, S2—commercially mature, and S3—fully mature). The results showed that 68 kinds of volatile flavor substances were identified in all green plum samples. The types and contents of such volatile substances experienced a V-shaped trend with an increasing degree of green plum maturity. During the S1 and S2 stages, aldehydes, ketones, and a small amount of alcohols were the main volatile flavor substances in the green plum samples. During the S3 stage, esters and alcohols were the most important volatile flavor components in the green plum pulp samples, followed by terpenes and ketones. YS had the most types and highest contents of volatile flavor substances in three stages, followed by GC and DZ. By using the PLS-DA method, this study revealed the differences in flavor of the different varieties of green plums at different maturity stages, and it identified eight common characteristic volatile flavor substances, such as ethyl acetate, 3-methylbutan-1-ol, and 2-propanone, produced by the different green plum samples during the ripening process, as well as the characteristic flavor substances of green plums at each maturity stage (S1–S3).

Aims We aimed to identify the optimal combination of selenium (from Na 2 SeO 4 ) and secondary elements required for obtaining the best nutritive characteristics and quality of 'Qingcui' plums. Methods Five treatments (Na 2 SeO 4 with MgSO 4 and CaSO 4 ) and a control treatment without Se, Mg, Ca, or S were applied to 2-year-old 'Qingcui' plum trees in a greenhouse. Plum leaves and fruit were analyzed for color, nutrient, and quality characteristics during the growing and deciduous seasons as well as the following year. Results Leaf color parameters, pigment content, and specific weight significantly improved by CaSO 4 addition during the growing and deciduous seasons. Ca and Mg contents during the growth, defoliation, and young leaf stages of the following year exhibited consistent trends under the different treatments, whereas Se and S contents differed according to the season and treatment. Thus, Mg and S showed high mobility and reutilization rates, whereas Ca and S showed poor mobility and reutilization rates. Leaf and fruit nutrient contents decreased in the order of Ca > Mg > S and S > Ca > Mg, respectively. The combination of 77 mg Na 2 SeO 4 , 10 g MgSO 4 , and 19 g CaSO 4 yielded optimal fruit quality in terms of fruit weight, hardness, and soluble solids and fruit Se content. A large amount of Ca was present in the cell wall, whereas S and Mg were mainly observed as soluble components. Conclusions Our study revealed the best combination of Se and secondary elements leading to optimal leaf nutrition and fruit Se content and quality in 'Qingcui' plums.

Sharka disease, caused by Plum pox virus (PPV) was first recorded in Bulgaria during the early twentieth century and since that first report, the disease has progressively spread throughout Europe and more recently to Asia, Africa, North and South America. Few PPV resistance genes have been found to naturally occur in Prunus and this has led to the investigation of biotech approaches to the development of resistance through genetic engineering (GE). A notable example of the utility of this approach is ‘HoneySweet’ plum. PPV protection in this case is based on RNA interference (RNAi) and resistance has been shown to be highly effective, stable, durable, and heritable as a dominant trait. Extensive testing and risk assessment of ‘HoneySweet’ in laboratory, greenhouse and in the field for over 20 years has demonstrated not only the effectiveness but also the safety of the technology. ‘HoneySweet’ has been cleared for cultivation in the USA. By the appropriate regulatory agencies. The development and regulatory approval of ‘HoneySweet’ demonstrate the ability of RNAi technology to contribute to the sustainability of stone fruit production in regions impacted by PPV. Although it has taken almost 100 years since the identification of sharka, we are now able to effectively protect stone fruit species against this disease through the application of GE.

Melatonin (MT) can improve plant resistance and fruit quality. The mechanism by which MT affects soluble sugar and organic acids accumulation in drupe fruits is not clear. In this study, 100 µmol/L MT was sprayed on the leaves of plum trees at the second stage of rapid fruit expansion (90 and 97 d after flowering), and the effects of MT on plum fruit quality and its effects on the soluble sugar-organic acid metabolism were investigated. At 28 d after MT treatment (at maturity), the longitudinal diameter, fruit weight, and vitamin C content of plum fruits were increased by 5.05%, 12.93%, and 56.09%, respectively, compared to the control. MT caused significant increase in the total soluble solids content and decreased the titratable acid content. MT increased the contents of total soluble sugar, sucrose, sorbitol, and citric acid after 21 and 28 days of treatment, while decreasing the contents of fructose, malic acid, quinic acid, and tartaric acid after 28 days of treatment. Additionally, MT increased the activities of sucrose synthase (catabolism direction), sucrose phosphate synthase, glucokinase, fructokinase, sorbitol oxidase, and NADP + -malic enzyme, and decreased the activities of soluble acid converting enzyme, cell wall insoluble converting enzyme, NAD + -sorbitol dehydrogenase, and NAD + -malic dehydrogenase after 21 or 28 days of treatment. Moreover, the differentially expressed genes (DEGs) after 21 and 28 days of treatment were accelerated starch and sucrose metabolism, galactose metabolism, fructose and mannose metabolism, as well as glycolysis, gluconeogenesis, and pentose phosphate metabolism pathways. In conclusion, exogenous MT increases soluble sugar content and decreases organic acid content in plum fruits by regulating various soluble sugar-organic acid metabolic pathways, thereby improving the fruit quality.