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In vitro propagation can be explored to overcome the constraint of limited planting material in plum. Although it ensures the production of plants in large number, but there are chances of somaclonal variations using this technology. Thus, clonal fidelity of in vitro raised plants should be checked to obtain true to type planting material prior to transplantation in the field. Genetic fidelity of in vitro cultures of plum (Prunus salicina) cvs. Santa Rosa and Frontier multiplied for 5 years (60 passages) through enhanced axillary bud proliferation was tested and compared with 2 year old in vitro raised and mother plants of respective cultivars using RAPD, ISSR and SCoT markers. Out of twenty-eight RAPD primers, eighteen produced 29 and 27 distinct bands in Santa Rosa and Frontier whereas, all of the fifteen ISSR primers screened generated clear reproducible bands in both the cultivars. In SCoT assay, eight primers out of twenty-six generated reproducible bands in both the cultivars. Homogenous amplification was observed in all the samples thereby confirming the genetic fidelity of tissue culture raised plants, thus suggesting that in vitro propagation using axillary buds is the safest mode for the production of clonal planting material in plum.

‘lucía myrtea’ and ‘victoria myrtea’ are early-season cultivars of Japanese plum (Prunus salicina Lindl.) typology, both characterized by their low chilling requirements, so their adaptation is ideal for warm growing areas in the current context of climate change. High productivity, high-quality fruit and attractiveness are three characteristics common to both new cultivars. ‘lucía myrtea’ and ‘victoria myrtea’ stand out for their attractive dark purplish skin; their striking and intense red flesh; and their excellent taste qualities, with firm, juicy and aromatic fruit. Another remarkable characteristic is the floral self-compatibility in the case of ‘victoria myrtea’, uncommon in Japanese plum cultivars and especially interesting for farmers. These new cultivars will contribute to improve the availability of early, red-flesh plums for the fresh market.

In Montenegro, stone fruit species are grown on intensive and semi-intensive commercial plantations. However, almond production is mainly organized on family gardens and for household consumption. During two seasons (2017–2018), we surveyed apricot, peach, nectarine, sweet cherry, Japanese plum, and almond orchards for the presence of bacterial diseases at different geographical locations in Montenegro. From leaf, petiole and fruit lesions, branch or twig cankers, and necrotizing buds, a total of 29 isolates were obtained and subjected to identification based on their morphological, pathogenic, biochemical, and molecular characteristics. Pathogenicity of the isolates was confirmed by reproducing the symptoms on leaves, fruits, and twigs of the corresponding host plants. The biochemical tests indicated that the isolates belong to Pseudomonas syringae. However, isolates’ characterization showed variation in their phenotypic and molecular features. The presence of the syrB gene and ice nucleation activity grouped most of the isolates within pathovar syringae. The results of rep-PCR using the BOX primer revealed high genetic diversity of isolates. Multilocus sequence analysis (MLSA), using four housekeeping genes, showed that 27 isolates belong to the genomic species 1, P. syringae sensu stricto, corresponding to P. syringae phylogroup 2. However, isolates from the same phylogroup 2 did not form a monophyletic group. One strain isolated from apricot was most distinct and similar to members of genomic species 2, phylogroup 3. All tested isolates showed significant levels of resistance to copper sulfate and high level of sensitivity to streptomycin sulfate in vitro.

Aydın, erik üretiminde Can erikleri ve Japon erikleri çeşitleri ile ilk sıralarda yer almakta, ancak ilde verim düşüklükleri ile karşılaşılmaktadır. Bu çalışmada, Aydın ekolojisinde yetiştiriciliği yapılan Can erikleri grubundan Papaz ve tozlayıcısı Aynalı ile Japon erikleri grubundan Friar ve tozlayıcısı Black Diamond çeşitlerinde çiçek tozu canlılığı, miktarı, çiçek tozu çimlenme düzeyleri ve çim borusu uzunluklarının belirlenmesi amaçlanmıştır. Çimlendirme ortamları olarak, %1 agarla katılaştırılan %0, %5, %10, %15 ve %20’lik sakkaroz ortamları ile %15 sakkaroz + %1 agar içeren 25, 50 ve 100 ppm borik asit (H3BO3) ortamları eklenmiştir. Araştırmada, en yüksek canlılık oranı %90.68 ile Friar çeşidinde saptanmıştır. Papaz çeşidi, %15 ve %20 sakkaroz ortamlarında sırasıyla %34.15 ve %31.63 çimlenme göstermiştir. Bir çiçekteki ortalama anter sayısında en yüksek değeri (37.60) Black Diamond çeşidi, bir anterdeki çiçek tozu sayısında en yüksek değeri (284.21 adet) Papaz çeşidi vermiştir. Bir çiçekteki çiçek tozu sayısı ise 4365 (Aynalı) ile 7447.50 (Black Diamond) arasında değişmiştir. En uzun çim borusu (3347µm), Black Diamond çeşidinde %10 sakkaroz ortamında ölçülmüştür. Borik asit uygulama dozlarının çim borusu uzunluğu üzerine belirgin etkisi görülmemiştir. Black Diamond ve Friar çeşitleri daha uzun çim borusu sağlamışlardır.

To evaluate the effect of the management system on soil quality, chemical and biological properties were measured in soils (0–20 cm depth) from Japanese plum orchards managed under organic and conv...

The present investigation was carried with the aim to study the effect of time of grafting and rootstock on graft success and growth in low chill peach cv. Shan- e-Punjab under sub tropics of Haryana (India). Study comprising of three different rootstocks viz., Peach cv. Sharbati seedling and Japanese Plum cv. Kala Amritsari and European plum cv. Green Gage rooted cuttings grafted on 9th and 25th January with three replications. Results reveal that advanced grafting (9th January) had significantly higher graft success (64.75%) and sprouting (69.02%) over 25th January, whereas, all growth parameters viz., plant height, percent increase in scion diameter, fresh and dry weight of shoot and root, relative water content, leaf nitrogen and total chlorophyll contents were significantly superior when wedge grafting was done on 25th January. On the other hand, among different rootstock, Sharbati seedling as rootstock performed better as compared to Kala Amritsari and Green Gage cutting for all the above recorded parameters. This investigation additionally gives the chances for further research to explore whether this pattern proceeds in the productive year of the peach plant.

Santa Rosa and Frontier are the major Japanese plum cultivars grown throughout the world. The present investigation was performed to understand the genetic relatedness among in vitro propagated plum cultivars Santa Rosa and Frontier using PCR based molecular markers. For the study, three arbitrary markers viz. RAPD (Random amplified Polymorphic DNA), ISSR (Inter-Simple Sequence Repeats) and SCoT (Start Codon Targeted) were used. In RAPD analysis, 18 primers out of 28 amplified and generated 33 scorable bands. The allelic variations when analysed, revealed 84 percent similarity between these two cultivars with highest polymorphic information content of 0.78. Similarly, 15 ISSR primers produced 73 amplicons with an average of 4.86 amplicon per primer and similarity coefficient ranging from 62 to 67 percent. Seven SCoT primers out of 26 resulted in a total of twenty- six scorable bands with 24 polymorphic bands. Cluster analysis from all the three markers used broadly divided plum cultivars santa rosa and frontier into two major clusters containing in vitro shoots, their progenies and mother trees of respective genotypes. The study concluded that these three marker systems were found to be effective in revealing genetic relationship of these two commercially important plum cultivars.

Plums are climacteric fruits with reduced shelf life and they represent a very appreciated product for fresh consumption. European consumers can find several plum cultivars that offer different organoleptic characteristics, flavor and aroma. In this study, chemical properties, such as total soluble solids (TSS), pH, titratable acidity, total phenolic and anthocyanin contents, aroma profile and sensory evaluation of seven plum cultivars were investigated. Significant differences in chemical properties were found in ‘Settembrine’ and ‘Angeleno’, the late ripening European plums that showed the highest TSS content and the lowest acidity values. As expected, a high level of anthocyanins was detected in red pulp and red flesh plums such as ‘Dofi Giudy’ and ‘Black Diamond’, though significant differences in their total phenolic amount were observed. ‘Dofi Giudy’, ‘Black Diamond’ and ‘Laroda’ showed the highest aroma profile among the investigated cultivars. Finally, a discrimination among the cultivars was obtained by combining the volatile profiles with a back-propagation neural network analysis (BPNN). The results showed that C6 compounds such as esters and aldehydes were strongly related to flavor perception of the panelists. ‘Dofi Giudy’ was the mostly appreciated plum due to its juiciness, sweetness and flavor intensity; furthermore, when compared to the other cultivars, it also showed remarkable levels of total soluble solids, total phenolic and anthocyanin contents.

In the present research the effect of rosehip oil (RO) coating on postharvest ripening process and fruit quality parameters of `President´ and `Royal Rosa´ plums was evaluated. Results show that the ethylene production was significantly reduced in coated plums with respect to controls either during storage at 20 ᵒC or at 2 ᵒC + 2 d at 20 ᵒC, as well as respiration rate. The increase on free and total 1-aminocyclopropane 1-carboxylic acid (ACC) was also decreased in RO coated plums. The evolution of fruit quality parameters related with the plum ripening process, such as firmness, colour Hue and total soluble solid (TSS)/titratable acidity (TA) ratio, during storage at both temperatures was also delayed by the application of RO coating, as well as the increase in phenolic and carotenoid concentrations and the antioxidant activity due to hydrophilic and lipophilic compounds. Thus, RO coating could be considered as a new eco-friendly tool to be applied in the agro-food industry to preserve plum quality and extend its storability.

A total of 24 Colletotrichum isolates were isolated from diseased Japanese plum (Prunus salicina) fruits showing chlorotic regions with whitish-brown sunken necrotic lesions and phylogenetic relationships among the collected Colletotrichum isolates were determined. A subset of 11 isolates was chosen for further taxonomic study based on morphology and molecular characteristics identified using the internal transcribed spacer (ITS) and beta-tubulin (TUB2) genes. Isolates in the C. acutatum complex were analyzed using partial sequencing of five gene regions (ITS, GAPDH, ACT, TUB2, and CHS), and C. gloeosporioides sensu lato (s.l.) isolates were analyzed using seven gene regions (ITS, TUB2, GAPDH, ACT, CAL, CHS-1, and ApMat). Morphological assessments in combination with phylogenetic analysis delineated four species of Colletotrichum including C. gloeosporioides sensu stricto (s.s.), C. nymphaeae, C. foriniae, and C. siamense; these data identify Colletotrichum fioriniae and C. siamense two new species associated with plum anthracnose in South Korea. Finally, the pathogenicity of these four species in the development of plum anthracnose in South Korea was confirmed by inoculations of plum fruit.

Flowering time is one of the most important traits in temperate fruit trees. Flowering time correlates with chilling requirements and ripening time. The mechanism controlling flowering time in these species could be conserved as suggested by the co-localization of QTL and the candidate genes for flowering time in several Prunus species. Currently, the molecular mechanisms underlying the regulation of flowering time remain poorly understood. In this study, three promising natural early-flowering/low-chilling-requirement mutants were identified and characterized: ‘Rojo Pasion Precoz’ and ‘Bulida Precoz’ in apricot (Prunus armeniaca L.) and ‘Santa Rosa Precoz’ in Japanese plum (Prunus salicina L.). The advancement in flowering date with respect to the wild types was around one week in the case of ‘Rojo Pasion Precoz’ apricot cultivar, more than two weeks in ‘Bulida Precoz’ apricot cultivar, and between 9–27 days in the case of ‘Santa Rosa Precoz’ Japanese plum cultivar. In addition, they were fingerprinted using 44 SSR (Simple Sequence Repeats) and 21 SNPs (Single Nucleotide Polymorphism) markers. Fingerprinting analysis confirmed identical marker profiles between the wild types and their mutants. These results support the hypothesis that a somatic mutation or a stable epi-allele may underlay the early-flowering phenotype.

Root disease caused by Armillaria mexicana and/or A. mellea is associated with tree mortality in peach (Prunus persica) orchards within their primary production zone of the Mexican sub-tropics. To improve management options for this disease, the resistance/susceptibility reactions of three Prunus rootstocks to infection by A. mexicana (isolate MEX85) and A. mellea (isolate MEX100) were evaluated under greenhouse and field conditions. Greenhouse phase: A. mexicana and A. mellea were independently inoculated on 14 trees (10-month old) of each rootstock in polycarbonate containers: P. persica × P. davidiana ‘Nemaguard’, P. persica landrace ‘Criollos of La Goleta’ genotypes, and P. salicina Japanese plum ‘Mondragon’. Four non-inoculated trees of each rootstock were maintained as controls, and variables related to tree growth and disease incidence were monitored for all trees. At 22 months post-inoculation with A. mexicana in the greenhouse, ‘Mondragon’ showed the lowest (2.5%) incidence of infected roots (IRI), while ‘Criollos of La Goleta’ and ‘Nemaguard’ rootstocks showed the highest (21.6 and 24.6%, respectively) IRI. With greenhouse-grown plants inoculated with A. mexicana, the dry weights and volumes of roots, and dry weights of entire plants were greater (2.2–4.8 times higher) for ‘Criollos of La Goleta’; however, abundant mycelia were observed within the root collar and lateral roots of this rootstock. In contrast, A. mellea inoculation resulted in relatively low (17.5%) incidence of root infection. In a commercial orchard (field phase) with high (35.3% symptomatic and dead trees) incidence of A. mexicana, 21 plants of ‘Mondragon’ (propagated via stem cuttings), ‘Criollos of La Goleta’, and P. mume ‘Japanese apricot’ were inoculated with the A. mexicana isolate. In the field, ‘Mondragon’ showed the lowest (1.0 disease severity at 66 months post-inoculation, P

Silverleaf is an important trunk disease of fruit crops, like Japanese plum. It is known that Chondrostereum purpureum produces wood discoloration, leaves silvering and tree decline, however, the information about the effects on fruit production is scarce. Therefore, the objectives of this study were to determine C. purpureum pathogenicity on Prunus salicina and 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 plating wood sections from the necrosis margin on culture media. Isolates colonies morphological and molecular characteristics accorded to C. purpureum (98%). Representative isolates were inoculated on 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, water potential, and fruit yield and quality were measured in healthy and Silverleaf diseased plum plants cv. ‘Angeleno’. Water potential was altered on diseased trees, and their yield was reduced in 51% (2019) and 41% (2020), compared to fruit from healthy plants. 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.

Research on the resistance to frost, susceptibility to sharka, flowering biology, fruit setting, yield, and ploidy levels of 36 Japanese plum cultivars (mostly hybrids of Prunus salicina with Prunus cerasifera) were carried out in 2015–2020 at the Experimental Orchard located in Dąbrowice near Skierniewice. Relatively mild winters with sporadic temperature drops to nearly −21 °C in January of 2017 and 2018 caused slight damage to several cultivars of Japanese plum insufficiently resistant to frost. The trees of most cultivars remained healthy, with no signs of damage. ‘Barkhatnaya’ and ‘Tatyana’ cultivars turned out to be very susceptible to sharka. ‘Herkules’ trees were the most vigorous. ‘Barkhatnaja’, ‘Blue Gigant’, ‘Shater’, and ‘Tatyana’ trees were characterized by weak growth. The trees of Japanese plum started flowering early, usually in the first or second decade of April. Most of the cultivars belonged to early season cultivars, the fruits of which ripened in July. Based on the assessment of tree productivity, ‘Barkhatnaya’, ‘Inese’, ‘Shater’, ‘Tatyana’, and ‘Vanier’ are the best for growing in the climate of Central Europe. ‘Tsernushka’, ‘Chuk’, ‘Dofi Sandra’, ‘Early Golden’, ‘Ewierch Rannyj’, ‘Yevraziya’, ‘Gek’, ‘General’, ‘Kometa’, ‘Kometa Late’, ‘Maschenka’, and ‘Naidyona’ trees also yielded well. ‘Blue Gigant’, ‘Black Amber’, and ‘Herkules’ had the largest fruits, and ‘Chuk’ and ‘Inese’ cultivars produced the smallest fruits. Among the assessed Japanese plum cultivars, those with round fruit, dark skin with various shades of purple, yellow flesh, and A cytometric analysis showed that almost all cultivars are diploid, except for ‘Herkules’ (possibly pentaploid) and ‘Yevraziya’ (possibly hexaploid or aneuploid).

XV EUCARPIA Symposium on Fruit Breeding and Genetics., Japanese plum is a diploid fruit tree species, member of the Rosaceae family, generated by hybridization of Prunus salicina with diverse Prunus species. Japanese plum cultivars show great variability for fruit skin and flesh color, which are both major objectives in plum breeding. Subsequently, molecular markers for early selection of these traits in breeding programs are highly desirable. Despite candidate genes for fruit color have been identified in several Rosaceae species, no validated markers have been described for Japanese plum yet. In Rosaceae family, MYB10 transcription factor has been described as the main gene determining anthocyanin pigment accumulation in fruits, which is responsible for red, purple and black coloration. In order to design a useful marker for marker-assisted selection (MAS), we have explored the variability of the MYB10 gene group in Japanese plum and its association with fruit color. A set of primers were designed targeting conserved MYB10 domains using sequences from peach genome. Primer combinations were tested using a reduced set of P. salicina accessions. The primer pair amplifying more polymorphic alleles was selected and used to genotype a collection of 78 Japanese plum cultivars. One allele, present in all 51 skin-colored accessions and absent in the rest, was found associated with anthocyanin accumulation. This dominant marker can effectively predict the presence or absence of fruit skin coloration caused by anthocyanin pigments.

BACKGROUND Soluble solids concentration (SSC), dry matter concentration (DMC) and flesh firmness (FF) are important fruit quality parameters in stone fruits. This study investigated the ability of a commercial visible/near-infrared (NIR) spectrometer to determine SSC, DMC and FF in nectarine, peach, apricot and Japanese plum cultivars at harvest. The work was conducted in summer 2019/2020 on 14 stone fruit cultivars at Tatura, Australia. Two sub-samples of 100 fruit each were collected before and after commercial maturity (± 5 days) in order to maximize sample variability. RESULTS Partial least square (PLS) regression models based on the second derivative of the absorbance in the 729-975 nm spectral region proved accurate for the prediction of SSC and DMC (R2CV > 0.750). Only the model generated for SSC in 'Golden May' apricot was less precise compared to other cultivars. No visible/NIR models were accurate enough to predict FF in the cultivars under study (R2CV

Hormone balance plays a crucial role in the control of fruit ripening. We characterized and compared hormone balance in two Japanese plum cultivars (Prunus salicina Lindl.), namely Santa Rosa, a climacteric type, and Sweet Miriam, its non-climacteric bud-sport mutant. We assessed hormonal changes in gene expression associated with hormone biosynthesis, perception and signaling during ripening on-the tree and throughout postharvest storage and in response to ethylene treatments. Non-climacteric fruit displayed lower ethylene levels than climacteric fruit at all stages and lower auxin levels during the initiation of ripening on-the-tree and during most of post-harvest storage. Moreover, 1-MCP-induced ethylene decrease also resulted in low auxin contents in Santa Rosa, supporting the role of auxin in climacteric fruit ripening. The differences in auxin contents between Santa Rosa and Sweet Miriam fruit could be the consequence of different routed auxin biosynthesis pathways as indicated by the significant negative correlations between clusters of auxin metabolism-associated genes. Ethylene induced increased ABA levels throughout postharvest storage in both ripening types. Overall, ripening of Santa Rosa and Sweet Miriam fruit are characterized by distinct hormone accumulation pathways and interactions.

UMR BFP - Equipe A3C; International audience; The chilling requirements for dormancy release and heat requirements for flowering were studied for three successive years in eleven Prunus salicina L. cultivars that spanned the range of flowering times in this species. Different methods for estimating chilling requirements were evaluated and compared, and correlations between chilling requirements, heat requirements and flowering date were established. The cultivars examined showed a range of chilling requirements (chill units, CU), spanning from 334.3 CU (‘Pioneer’) to 987.5 CU (‘Songold’). The heat requirements for flowering ranged between 5990 and 9228 growing degree hours. The chilling requirements were significantly different among cultivars, whereas no cultivar effect was found for the heat requirement values. In addition, chill portions were the variable that correlated the most with flowering date in Japanese plum. The dissection of flowering date into chilling and heat requirements indicates that chilling requirements is the main variable driving the variation of flowering time within Japanese plum cultivars.

Moisture loss and postharvest shrivelling of some Japanese plum cultivars result in significant financial losses in the South African stone fruit industry. Even though fruit are stored at optimal temperatures and packaging solutions are implemented to reduce shrivel, the incidence of shrivel is still unacceptably high in susceptible cultivars. Fruit peel water vapour permeance (PH2O) can be calculated to determine the proneness of a cultivar to moisture loss. Knowledge of the status of the PH2O prior to harvest and the variation between cultivars, orchards and seasons could indicate whether newly developed cultivars are prone to postharvest shrivel. This could assist in determining the optimum handling protocols for susceptible cultivars to reduce potential moisture loss. The PH2O of various cultivars were determined during 2015/16 and 2016/17. In addition, to establish whether a relationship exists between postharvest fruit moisture loss and shrivel, weight loss and shrivel incidence was recorded on individual fruit of the cultivars Sapphire, Laetitia and African Delight™ during 2016/17. PH2O varied between seasons, cultivars and orchards. In ‘African Rose’, ‘Ruby Sun’ ‘Ruby Star’ and ‘Sapphire’, high PH2O corresponded with known shrivel susceptibility. ‘Songold’, ‘Fortune’ and ‘Angeleno’ are not prone to shrivel and these cultivars had a low PH2O. However, ‘Laetitia’ and ‘African Delight™’ had low PH2O, even though both cultivars are prone to shrivel. Pre-harvest moisture loss and PH2O could therefore not be used to predict shrivel susceptibility successfully for evaluated cultivars.

Genotyping by sequencing (GBS) provides a large quantity of useful data suitable for the identification of single nucleotide polymorphisms (SNPs), facilitating accurate genomic studies in plant species. In this study, GBS-based SNPs were used to characterise 11 Japanese plum cultivars and to explore their natural allelic diversity in relation to the most important phenology events (flowering date, ripening date and fruit development period) and fruit quality traits (weight, shape, skin and flesh colour, over colour, skin and flesh chlorophyll index, flesh firmness and soluble solids concentration). GBS-based SNPs were shown to be a powerful tool for genetic diversity and other genomic studies where SNP markers were related to several traits, particularly for flowering date, ripening date, fruit development period, skin chlorophyll degradation, flesh chlorophyll degradation and flesh colour. These results represent a preliminary approach using GBS as a possible breeding tool in current and new Japanese plum breeding programmes.

High irradiance and high temperatures decrease Japanese plum (Prunus salicina Lindl.) quality by causing sunburn. We manipulated orchard conditions to determine how resultant light and temperature affected fruit quality and sunburn. In the 2013/14 season, early summer pruning, late pruning and a no pruning control were applied in an ‘African Delight’ plum orchard trained to a staggered V trellising system in the Western Cape Province of South Africa. In 2014/15, 20% shade net was incorporated during the hottest part of the season in a split plot design. Shade net and a no shade net control formed the main plots while pruning treatments were subplots. Photosynthetic photon flux (PPF), fruit surface temperature (FST) and sunburn were progressively assessed on two hourly intervals on typically hot days for upper, mid and lower canopy positions. PPF and FST generally decreased from top to bottom of the canopy. Upper canopy positions had bigger and softer fruit with higher sunburn incidence and higher total soluble solids (TSS). Fruit that developed sunburn received >50% PPF of full sun on average while average FST exceeded 35°C. Early summer pruning improved early light penetration but enabled vegetative regrowth for filtered light during the hottest part of the season resulting in bigger and redder fruit with higher TSS and low sunburn. Delayed pruning increased sunburn with no increase in fruit size, while the control delayed fruit maturity and reduced fruit size. The shade net reduced sunburn caused by delayed summer pruning. While it was apparent that proper timing of orchard light manipulation is essential, the use of shade net still has to be evaluated over the entire growing season to ascertain its full value.

6 Pags.- 2 Tabls. The definitive version is available at: https://www.actahort.org/index.htm, Graft compatibility for new Prunus rootstocks recently introduced into the Spanish market or under selection in public and private programmes is assessed in nursery trials. Part of the evaluated material belongs to the Aula Dei Experimental Station (EEAD-CSIC) selection program in Zaragoza, Spain. Another group of rootstocks under test is from the private nursery Agromillora Iberia, S.L. Some of those rootstocks showed good adaptation to Mediterranean growing conditions and resistance to root-knot nematodes. As control, peach-almond (‘GF 677’), peach × P. davidiana (‘Cadaman’), other interspecific plum-based rootstocks (‘Damas GF 1869’, ‘Ishtara’) and different plum species (P. cerasifera: ‘Adara’; P. domestica: ‘Constantí 1’; P. insititia: ‘Adesoto’ and other ‘Pollizo de Murcia’ clones, ‘Saint Julien A’) are used. New evaluated rootstocks include: ‘Densipac R 20’ (P. besseyi × P. cerasifera), ‘Nanopac R 40’ (P. dulcis × P. persica), ‘Replantpac RR’ (P. dulcis × P. cerasifera), ‘AP 45’ [(P. besseyi × P. salicina) × P. armeniaca], ‘Aprimed AP 65’ [(P. armeniaca L. × P. cerasifera Ehrh) × P. pumila L. var. besseyi], and ‘LC 52’ (P. cerasifera × P. maackii), among others. To determine graft-compatibility, commercial cultivars of different Prunus species were budded on some of the evaluated rootstocks. They include: ‘Moniquí’ and ‘Portici’ (apricot); ‘Lauranne’, ‘Nonpareil’, ‘Penta’ and ‘Soleta’ (almond); ‘Angeleno’ and ‘Golden Japan’ (Japanese plum); ‘Big Top’ and ‘Sumergrand’ (nectarine) and ‘Aida’, ‘Carmen’, ‘Cordia’, ‘Ferrovia’, ‘Kovics’, ‘Krupnoplodnaja’, and ‘Sandor’ (cherries). Several degrees of graft incompatibility have been observed for the ‘translocated’ type of incompatibility. In general, peach-almond hybrids and slow-growing plums (P. domestica and P. insititia plums as ‘Adesoto’ and other ‘Pollizo de Murcia’ clones) were graft-compatible with peach, almond and Japanese plum tested cultivars. However, in the case of P. cerasifera, P. besseyi and interspecific hybrids with these species, performance differed substantially depending on the evaluated genotype., This study was funded by the Spanish Ministry of Economy and Competitiveness (MINECO) grants CDTI IDEI-20130949, AGL2011-24576, and AGL2014-52063-R and was cofunded by the FEDER and the Regional Government of Aragón (A44) with European Social Fund. Alex Salazar was supported by a fellowship from the Secretary of Education, Science and Technology (SENESCYT) of the Ecuadorian Government.

During the last two seasons, an unusual fruit rot was observed in four orchards of sweet Japanese plum (Prunus salicina) cultivars located in the Chilean Central Valley (30°00'S, 70°42'W). The incidence was 5% in Black Majesty, 4% in Red Lyon, and 6% in Sweet Mary cultivars in 2020. Fruits in the field showed a firm, dehydrated, and slightly sunken rot on the blossom end, along with rough and irregular epidermis in the affected area. Internally, the fruit flesh appeared light to dark-brown or olive-green. Symptomatic fruits (n=119) were superficially disinfected (75% ethanol) and, pieces of the pericarp (3 x 3 mm) were removed and placed on potato dextrose agar (PDA). Isolates of Alternaria spp. were obtained and 9 of these were selected for identification. Colonies were dark olive to gray-brown with white margins, small, catenulate and muriform conidia, produced in single or branched conidiophores. Isolates produced brown to golden-brown, ovoid, ellipsoidal to obclavate conidia with dimensions of 19.7 to 26.7 × 10.0 to 11.9 μm with two to four transverse and zero to three longitudinal septa on 0.05× PDA (Pryor and Michailides 2002) after 7 d at 20°C under 10/14 h light/dark cycles. A molecular analysis was performed by sequencing the nuclear genes RNA polymerase II subunit (RPB2), plasma membrane ATPase (ATP), and the calmodulin (Cal) gene using primers RPB2-5F2/fRPB2-7cR, ATPDF1/ATPDR1, and CALDF1/CALDR1, respectively (Lawrence et al. 2013; Woudenberg et al. 2013). A BLAST search revealed the presence of Alternaria spp. with a 99% to 100% identity with the reference sequences of A. alternata (JQ905182, JQ671874, JQ646208), A. arborescens (JQ646487, JQ671880, JQ646214), and A. tenuissima (JQ811961, JQ811989, JQ646209). Maximum parsimony phylogenetic analysis confirmed the identifications. Sequences were deposited in GenBank as numbers MW514249 to MW514257, MT872324 to MT872332, and MT872314 to MT872322 for RPB2, ATP, and Cal sequences, respectively. All these Alternaria isolates were deposited in the Coleccion Chilena de Recursos Geneticos Microbianos - INIA, Chillan Chile (RGM3069 to RGM3077). Pathogenicity of A. alternata (n=4), A. arborescens (n=3) and, A. tenuissima (n=2) was tested in Red Lyon plum fruits. Plums were disinfected in 1% sodium hypochlorite for 2 min, rinsed in sterile distilled water for 1 min and dried on absorbent towels in a laminar flow hood. Then, the plums were wounded on the blossom end with a sterile needle (1 x 0.5 mm), inoculated with 10 µl of a conidial suspension (106 conidia/ml), wrapped with Parafilm and maintained in a humid chamber (>95% relative humidity). An equal number of fruits wounded and inoculated with sterile water were used as a control. After 7 days at 20°C, all inoculated fruits developed a dark-brown firm rot with lesion lengths of 24.4 (±3.0) mm, 19.6 (±0.7) mm, and 16.8 (±2.4) mm for A. alternata, A. arborescens and A. tenuissima, respectively. A. alternata was the most aggressive species (P < 0.001). Control fruits remained asymptomatic. Koch's postulates were fulfilled after the re-isolating the causal agent from the border of the lesions. Leaf spots and fruit rots caused by Alternaria isolates have been reported in stone fruits, including plums (Kim et al. 2005; Long et al. 2021; Moosa et al., 2019; Yang et al. 2014). To our knowledge, this is the first report of A. alternata, A. arborescens, and A. tenuissima associated with fruit rot in sweet Japanese plum cultivars in the field, in Chile.

Prunus domestica (European plum) and Prunus armeniaca (apricot) are related species which can be hybridized. However, there are only very few reports on true interspecific hybrids between P. domestica and P. armeniaca. These hybrids must not be confused with the so called pluots or plumcots which are hybrids between P. salicina (Japanese plum) and P. armeniaca. In 2005, a program for breeding interspecific hybrids between P. domestica and P. armeniaca was initiated at Technische Universitat Munchen. As female parent, a P. domestica clone with hypersensitivity resistance to Plum pox virus (PPV) was used. As male parent, apricot cultivars with different degrees of susceptibility to PPV were chosen. Several interspecific hybrids were obtained. Leaves, shoots and fruits of the seedlings are intermediate between European plum and apricot. The seedlings were tested for their resistance to PPV. Interspecific hybrids with strong resistance to PPV could be obtained. To the best of our knowledge, this is the first report on the generation of PPV resistant hybrids between European plum and apricot. The hybrids could help to better understand the genes which are involved in hypersensitivity resistance to PPV. Moreover, the interspecific hybrid can be used for transferring the PPV resistance to the apricot genome by repeatedly backcrossing them with apricot. The interspecific hybrids represent a new kind of fruit species as the outer and inner fruit traits are intermediate between the parent species.

The Japanese plum ‘Black Doris’ (Prunus salicina) is a self-infertile early-flowering crop so insufficient cross pollination and lack of pollinators could be factors to explain reported poor fruit set. This project assessed the relative abundance of flower visitors within a plum orchard and their movements among three orchards, as part of a wider study on plum pollination. Insect surveys conducted over three days across one orchard in 2014 identified a total of 479 individual pollinators. Honey bees represented 94.6% of all pollinators observed. To assess pollinator movement across the crop, 140 individual flower visitors were followed over a five-day period in 2014 and again in 2015 across three orchards. Bumble bees moved further within the orchard and visited more trees per minute than foraging honey bees, while silvereyes visited more than twice as many flowers per minute than any other insect flower visitor.

Stone breakage causes significant financial losses for the South African Japanese plum export industry as affected fruit must be marketed as Class 2 according to OECD (Organisation for Economic Co-operation and Development) standards. While information exists on split pit in peaches no information could be obtained regarding the development and/or possible protocols to reduce broken stones in Japanese plums. The main aim of this study was, therefore, to determine when and why broken stones develop during fruit development in Japanese plums in an effort to find possible ways to reduce the incidence of the defect in Japanese plums produced in South Africa. X-ray micro computed tomography was used to compare the fruit growth characteristics and endocarp density of ‘Laetitia’ and ‘Sapphire’ (which are highly susceptible to stone breakage) and ‘Songold’ (which is less susceptible to stone breakage) plums during the stone hardening phase of fruit development. Similar to what was found in peaches, this study found that endocarp lignification in Japanese plums started at the stylar end of the stone and progressed towards the stem end between 28–63 days after full bloom. Lignification was accompanied by an increase in endocarp density. The inner lining of the plum stones started to harden first, after which lignification continued outwardly. Clear differences were observed between plum cultivars and seasons in the incidence of broken stones. In all instances broken stone manifestation coincided with the commencement of rapid fruit growth before the stones were completely hardened. Since the stones were not completely hardened by the time rapid fruit growth started, the stones were not able to resist the strong pulling forces of the growing mesocarp and were pulled apart.

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 Queen Garnet Plum (QGP), a cultivar of Japanese plum (Prunus salicina Lindl.), was developed as a high anthocyanin plum in a Queensland Government breeding programme. Anthocyanins have been associated with various health attributes, including diabetes control, cardiovascular disease prevention and anti-inflammatory activity. This study was aimed at identifying the changes in physiochemical properties and important phytochemicals of QGP when stored under two storage temperatures. QGP from two growers were stored at 4 and 23 oC for 0, 4, 7, 10 and 14 days. At the end of each storage period the peel, outer flesh (up to 7 mm from the peel) and inner flesh were separated and analysed for chroma, total soluble solids (TSS) and titratable acidity (TA). The grower source had a significant effect on the measured parameters when considered as a covariate. Chroma values of the peel, inner and outer flesh were significantly (P < 0.05) different at 4 and 23 oC, after 14 days. There was no significant difference in the inner flesh TSS (IF-TSS) and outer flesh TSS (OF-TSS) between the different storage temperatures, but compared to day 0, after 14 days IF-TSS and OF-TSS were significantly (P < 0.05) lower. TA of the inner and outer flesh were significantly (P < 0.05) different at the two storage temperatures, but only the inner flesh TA was significantly (P < 0.05) different after 14 days. Further analysis is in progress for anthocyanins, total phenolics, carotenoids, folates and vitamin C. The current study indicates that QGP is climacteric and grower source, storage temperature and time as well as tissue can significantly affect the studied physicochemical parameters.

The Japanese plum (Prunus salicinaLindl.) is one of the most important stone fruit crops in China. High-density linkage map is valuable resources which enhance functional genomics and genetic breeding studies. So far several Japanese plum linkage maps have been reported using different kinds of molecular markers; however, the marker numbers and chromosome coverage are limited. Recently, a newly developed strategy which genome sequencing towards specific-locus amplified fragments (SLAF) markers, has been proven to be powerful for rapid genotyping of genome-wide markers and for high-density genetic map construction. In this study, SLAF was used to genotype markers with 114 F1 seedlings from the ‘09–16’ × ‘Fortune’ cross. Suitable SLAF markers (160,344 out of 343,436,902 pair-end reads) were chosen to conduct genetic map construction, 16.31% of which were polymorphic. The overall integrated map contained 3,341 high quality SLAFs and 720 loci that were grouped in eight genetic linkage groups with a total length of 869.9 cM and an average distance of 1.21 cM, and only five gaps with a genetic distance > 5 cM between adjacent markers occurred in linkage group (LG) 3 and LG6. The number of markers with each LG ranged from 82.3 cM (LG3) to 138.3 cM (LG1). Aligning the map against the peach reference genome sequence (Prunus persica L.) indicated a strictly co-linear relationship between the LGs and peach genome, demonstrating the markers on ours LGs were well ordered. Overall, our studies identified large-scale of genetic markers and constructed high-density linkage maps for Japanese plum, which will obviously provide a solid foundation for marker-assisted selection and sequence assembly of the Japanese plum reference genome.