Search

Consumption of anthocyanins from fruit sources may exert protection against hypertension and improve cognition. However, the effect of dose timing in studies is rarely considered. We hypothesized that timed-dose consumption of juice from an anthocyanin-rich Japanese plum variety (Queen Garnet plum, QGP) will have acute and dose-timing effects on cardiovascular responses, cognition, and urinary anthocyanin excretion profiles. Our study objective was to investigate the impact of plum juice on these health parameters. Twelve older (65+ years) and 12 younger (18-45 years) adults participated in an acute crossover study. Participants received, randomly, either 1 × 300 mL or 3 × 100 mL plum juice over 3 hours on 2 different occasions with a 2-week washout period. A battery of cognitive tasks was administered at 0 and 6 hours on each study day. Blood pressure (BP) and urinary anthocyanin/metabolite excretion profiles were measured over 24 hours. Area under the curve for BP was calculated (0-6 hours). A significant reduction in BP and cardiovascular responses was observed in both age groups which was more obvious in the older age group on the single dose for systolic BP, diastolic BP, mean arterial pressure, and heart rate (P values = .035, .028, .017, and .006, respectively). No significant difference was observed between dose-timing regimens for either age group. There was no observed effect on cognition. Native QGP anthocyanins, as well as methylated/glucuronidated metabolites, were detected in urine with no significant differences between age groups or dose timing. High-anthocyanin plum juice significantly reduced BP, but dose timing did not appear to be a significant factor in the potential acute BP-lowering effect of QGP juice.

4 Figuras; 2 Tablas; 25 Páginas, Although several chlorophyll metabolites have been shown to exert prominent benefits to human health when consumed, the battery of linear chlorophyll derivatives (phyllobilins) presents in fruits is poorly understood. Yellow chlorophyll catabolites (YCCs) are a new kind of phyllobilins recently identified in senescent leaves, probably arising from an oxidative process of the terminal chlorophyll catabolites, NCCs (non-fluorescent chlorophyll catabolites). This work deals with the characterization by first time of this kind of phytochemicals in edible fruits. Two YCCs have been identified in yellow Japanese plums, one (Ps-YCC1) previously described in the senescent leaves of Cercidiphyllum japonicum Siebold & Zucc. and Ps-YCC2, a chlorophyll catabolite structure described by first time in the edible parts of Japanese plum fruits. These YCCs were characterized by high-resolution MS/MS, describing the specific fragmentation (ring A) and the absence of the typical cleavage of phyllobilins (ring D), as a consequence of the unsaturated bond at C15–16 typical of YCCs, allowing the differentiation from NCCs. To the already known array of phenolic acids, anthocyanins and carotenoids, NCCs and YCCs may contribute to the antioxidant potential of these fruits, a potential that deserves attention and future research, considering the photochemical and photophysical behaviour of this group of tetrapyrrolic breakdown products., This work was supported by the Comisión Interministerial de Ciencia y Tecnología (CICYT-EU, Spanish and European Government, AGL 2015-63890-R).

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.

Iran is amongst the countries in the world widely known for cultivation of Prunus spp. (or stone fruits). It is both a centre of origin and diversity of the stone fruits. Numerous wild species as well as many cultivars and landraces of these fruit crops are important genetic resources today in Iran and can be used for improvement and breeding of scion and rootstock cultivars which are resistant to many biotic and abiotic stresses through modern genomics and genetic technologies. This paper discusses the distribution, ethno-botany, diversity and utilization of wild and domesticated genetic resources of stone fruits including almond (Prunus dulcis (Miller) D. A. Webb.), peach and nectarine (P. persica Batsch), European and Japanese plum (P. × domestica L., and P. salicina L., respectively), sweet and sour cherry (P. avium L., and P. cerasus L., respectively), and apricot (P. armeniaca L.), all of which are members of the Rosaceae family. The goal of this paper is to highlight the importance of Iran as a main contributor to the diversity of Prunus genetic resources in the world, as well as, present major achievements regarding identification, collection, evaluation, conservation and utilization of this valuable genetic resource in Iran.

In order for the Japanese Plum to reach distant markets with adequate consumption quality, it is necessary to determine not only the best harvesting time but also the most appropriate postharvest technologies that allow the correct ripeness after the distribution process. This paper addresses the combined effect of the harvesting time (H1, H2 and H3) with or without 1-MCP (T and C) treatment and the postsharvest storage in different temperature regimes (0 °C, 8 °C and dual temperature regime, 0/8 °C). The ‘Songold’ plum was kept for 30 and 50 days in cold storage and at 20 °C for 5 days after that (shelf-life, SL). For each analysis date, physical and chemical quality parameters were established (weight loss, firmness, colour, total soluble solids and acidity), together with postharvest damage (chilling injuries and decay). In general, the 1-MCP reduced the firmness loss and colour changes (L* and b*), maintaining the acidity of the fruit at rates close to those of the ones at harvest. The use of 1-MCP allows us to market the fruit at a more advanced ripening stage and to store it at a higher temperature without quality loss. Chilling injuries (CI) were the most relevant damages, mainly in H2 at 8 °C after 50 + 5 days. 1-MCP appears to reduce the impact of CI but not decay.

Growth and productivity characteristics including: initial and final fruit set, yield per tree, trunk cross-sectional area, yield efficiency and fruit weight were studied in ten cultivars of Japanese plums in the Belgrade area for the period of three years (2013-2015). Initial fruit set ranged from 5.6 to 44.4%, and the final fruit set from 2.6 to 23.36%. The high yield per tree (over 10 kg) was obtained in cultivars ‘Obilnaja’ and ‘Morettini 355’, whereas the low yield (under 5 kg) was obtained in cultivars ‘Strival’, ‘Black Amber’, ‘Early Angeleno’ and ‘Autumn Giant’. The lowest vigor was observed in the cultivar ‘Golden Plum’, and the highest in the cultivar ‘Strival’. The majority of cultivars had a very large fruit (over 50 g). The yield was strongly positively correlated with initial and final fruit set (r = 0.84**; r = 0.92**, respectively). Fruit weight was moderately negatively correlated with initial and final fruit set (r = -0.67*; r = -0.63*, respectively). U periodu od tri godine (2013-2015) kod deset sorti japanske šljive na području Beograda proučavane su karakteristike rasta i rodnosti: inicijalno i finalno zametanje plodova, prinos po stablu, površina poprečnog preseka debla, koeficijent rodnosti i masa ploda. Inicijalno zametanje plodova je variralo u rasponu 5,6−44,4%, a finalno zametanje 2,6−23,3%. Visok prinos po stablu (preko 10 kg) imale su sorte Obilnaja i Morettini 355, dok su nizak prinos (ispod 5 kg) imale sorte Strival, Black Amber, Early Angeleno i Autumn Giant. Najmanju bujnost je imala sorta Golden Plum, a najveću Strival. Većina sorti je imala krupan ili vrlo krupan plod (preko 50 g). Prinos je bio u jakoj pozitivnoj korelaciji sa inicijalnim i finalnim zametanjem plodova (r = 0,84**, odnosno r = 0,92**). Masa ploda je bila u srednje jakoj negativnoj korelaciji sa inicijalnim i finalnim zametanjem plodova (r = -0,67*, odnosno r = -0,63*).

VIII International Symposium on Irrigation of Horticultural Crops., The response of fruit growth to irrigation depends on the cellular processes which form the fruit. We compared plum mesocarp (pulp) growth and development under two irrigation regimes: full irrigation (FI) that provided 100% of estimated crop evapotranspiration (ETc) and regulated deficit irrigation (RDI) without irrigation from 56 to 120 days after full bloom (DAFB) and full irrigation for the rest of the season. The experiment was performed in 2012 in a high-density plum (Prunus salicina 'Angeleno', on Mariana 2624 rootstock) orchard in La Orden regional experimental station (Extremadura, southwest Spain). Fruit central transverse mesocarp sections were observed by microscope, and mesocarp area, mesocarp cell number and mesocarp cells area determined at the onset of the deficit period (70 DAFB), the end of that period (120 DAFB) and at harvest (180 DAFB). Following the deficit period, fruit fresh weight in the deficit treatment was 68% of fully irrigated and mesocarp area, mesocarp cell number and mesocarp cells area were 31, 17 and 18% less, respectively. At harvest the deficit irrigated fruits had partially recovered, reaching 80% fresh weight of the control, and all cellular parameters and tissue sizes were similar to the fully irrigated fruits. These results confirm the capacity for plum fruit growth recovery following mid-season water stress, and that both cell and tissue processes contribute to recovery.

The genetic diversity of 14 Japanese plum (Prunus salicina Lindl) landraces adapted to an ecosystem of alternating flooding and dry conditions was characterized using neutral simple sequence repeat (SSR) markers. Twelve SSRs located in six chromosomes of the Prunus persica reference genome resulted to be polymorphic, thus allowing identification of all the evaluated landraces. Differentiation between individuals was moderate to high (average shared allele distance (DAS) = 0.64), whereas the genetic diversity was high (average indices polymorphism information content (PIC) = 0.62, observed heterozygosity (Ho) = 0.51, unbiased expected heterozygosity (uHe) = 0.70). Clustering and genetic structure approaches grouped all individuals into two major groups that correlated with flesh color. This finding suggests that the intuitive breeding practices of growers tended to select plum trees according to specific phenotypic traits. These neutral markers were adequate for population genetic studies and cultivar identification. Furthermore, we assessed the SSR flanking genome regions (25 kb) in silico to search for candidate genes related to stress resistance or associated with other agronomic traits of interest. Interestingly, at least 26 of the 118 detected genes seem to be related to fruit quality, plant development, and stress resistance. This study suggests that the molecular characterization of specific landraces of Japanese plum that have been adapted to extreme agroecosystems is a useful approach to localize candidate genes which are potentially interesting for breeding. Instituto de Biotecnología Fil: Acuña, Cintia Vanesa. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Biotecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Rivas, Juan Gabriel. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Biotecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Brambilla, Silvina Maricel. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética; Argentina Fil: Cerrillo, Teresa. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Delta del Paraná; Argentina Fil: Frusso, Enrique. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Recursos Biológicos; Argentina Fil: Garcia, Martin Nahuel. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Biotecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Villalba, Pamela Victoria. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Biotecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Aguirre, Natalia Cristina. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Biotecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Sabio Y Garcia, Julia Verónica. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Biotecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Martinez, Maria Carolina. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Biotecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Hopp, Horacio Esteban. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Biotecnología; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Marcucci Poltri, Susana Noemi. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Biotecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

The effects of the application of the chemical thinner Armothin® on fruit set, yield and quality of Japanese plum (Prunus salicina Lindl.) cv. ‘Fortune’ were studied during two seasons in Central Chile (34.56°S, 71.5°W). Trees were sprayed with Armothin® at 0.5%, 1% and 2% concentrations. All thinning treatments reduced the fruit set and fruitlet number (fruitlets/50 cm of branch). Armothin® at 2% conc. was the most aggressive treatment, drastically reducing the fruit set from 85.9% and 82.9% of the control and crop load to unprofitable levels during both seasons. Chemical thinning treatments at the two lowest concentrations (0.5 and 1%) did not significantly alter the crop load compared with the unsprayed control during both study seasons. Thinning costs were reduced (Armothin® 0.5%, 25.0% and 21.5% of the control treatment and Armothin® 1%, 24.6% and 24.1% of the control, during the first and second season, respectively). In general, chemical thinning increased the fruit size and total soluble solids content (TSS). Taking into account the ef- fects on thinning, crop load, fruit quality and thinning costs, Armothin® 1% and Armothin® 0.5% are the most advantageous treatments in the case of this study.

Monilinia fructicola, causal agent of brown rot, is one of the most important fungal pathogens of stone fruit. In the summer of 2011, Japanese plum fruit of ‘Larry Ann’ (Prunus salicina Lindl) showing symptoms of fruit rot disease were detected and collected from trees in an experimental field at Alcalá del Río (Seville), southwestern Spain. Fruit rot lesions were brown, sunken, and covered with grayish brown tufts or pustules. The majority of infected fruit became dry and mummified on the trees after 30 days. Symptoms were similar to those caused by three Monilinia species, M. laxa, M. fructigena, and M. fructicola (2). Pieces of infected tissue, previously disinfested in 0.6% NaOCl, were placed on potato dextrose agar (PDA) amended with 50 μg of streptomycin per liter and incubated at 22°C with a 12-h photoperiod for 15 days. The isolates produced abundant, grayish white mycelium, which after sporulation became hazel in color, and colonies displayed concentric rings. Colonies produced scarce conidia, which were arranged in branched, monilioid chains. Conidia were one celled, hyaline, ellipsoid to lemon shaped, and measured 15.42 ± 1.91 × 8.02 ± 0.9 μm. The morphological data and growth rates match the description of M. fructicola (Winter) Honey (2–4). Fungal identification was confirmed by PCR using genomic DNA extracted from the mycelia of pure cultures. The DNA was amplified with a common reverse primer and three specific forward primers obtained from a sequence-characterized, amplified region that distinguishes between M. fructicola, M. fructigena, and M. laxa. The size of the amplified fragment (a product of 535 bp) fit with the one described for M. fructicola (2). To confirm the pathogenicity of the isolate, mature ‘Larry Ann’ and ‘Sungold’ plum fruits (six fruits per cultivar) were inoculated by placing an agar plug from the edge of an actively growing colony on PDA directly on the fruit surface. After 5 days of incubation, typical brown rot symptoms developed on inoculated fruit and the fungus was successfully reisolated, thus fulfilling Koch's postulates. No symptoms appeared on control fruit. To our knowledge, this is the first report of M. fructicola on plums in southwestern Spain. M. fructicola is a quarantined pathogen in Europe and has been reported on imported apricot and nectarine (1) and peach in several European countries (3,4). References: (1) E. Bosshard et al. Plant Dis. 90:1554, 2006. (2) M. J. Côté. Plant Dis. 88:1219, 2004. (3) A. De Cal and I. Gell. Plant Dis. 93:763, 2009. (4). C. Pellegrino et al. Plant Dis. 93:668, 2009.

Dapple plum and peach fruit is a widely distributed disorder of plum and peach resulting in significant economic losses (4). During a survey for the presence of Hop stunt viroid (HSVd) on stone fruit trees in Greece, samples from 30 European plums (Prunus domestica L., cvs. President, Tuleu Grass), 45 Japanese plums (Prunus salicina Lindl., cvs. Angeleno, Diamond, Santa Rosa), 12 cherry plums (Prunus domestica L. var. insititia (L.) Fiori & Paoletti of unknown cultivar), and 107 peaches (Prunus persica (L.) Batsch, cvs. Red Haven, Elberta, June Gold, Spring Crest, Lemonato) were collected in several orchards around Greece. Their fruit skin symptomatology indicated viroid infection (reddish dappling blotches and cracks in European and Japanese plum, green dappling in cherry plum, and light colored blotches and lines in peach). Samples were screened with tissue-print hybridization (TPH) for HSVd using a full length DIG-labelled riboprobe deriving from in vitro transcription of the positive control, a citrus isolate of HSVd (G. Vidalakis, CCPP, University of California, Riverside). In total, 44 out of the 194 trees surveyed were HSVd-positive with TPH. For a small number (40) of TPH-positive field samples, TNA phenol extraction from fruit skin, leaves, and bark and one-tube two-step reverse transcription (RT)-PCR assays followed, using a standardized protocol (3) with two different primer pairs, one new primer pair (this study) and a previously reported primer pair (2). RT-PCR analysis showed the presence of HSVd in peach and Japanese plum in prefectures Pella (Central Macedonia), Achaia, and Korinthia (Peloponnesus) and in cherry plum in Achaia (Peloponnesus). Six of 11 Japanese plums (cvs. Angeleno, Santa Rosa), 2 of 12 cherry plums, and 8 of 12 peaches (cvs. Spring Crest, Red Haven) examined were found HSVd-infected, but none of the five European plums were. Nucleotide sequence analyses of purified and cloned amplicons from peaches and Japanese and cherry plums revealed sizes of 297 to 308 nt and similarity to sequence variants of other HSVd isolates previously characterized: 95 to 97% identity with the Moroccan isolates apr.9, apr.10, apr.11, and apr.12 and the Spanish isolate apr.4 from apricot (1) (GenBank Accession Nos. AJ297825 to AJ297828 and Y09346, respectively). For confirmation of HSVd presence in field trees, 10 Japanese plums cv. Angeleno, 10 peaches cv. June Gold, and 10 peaches cv. Spring Crest, HSVd-negative (TPH), were bud- or chip-grafted from two of the aforementioned Japanese plums cv. Angeleno and two of the aforementioned peaches cv. Red Haven. Two years later, five Japanese plum trees (cv. Angeleno) and five peach trees (three cv. Spring Crest and two cv. June Gold) were found HSVd-positive with TPH; no fruits were observed to produce fruit symptoms as the grafted trees were kept in an insect-proof greenhouse (no bees for cross-pollination). To our knowledge, our investigation reports for the first time the occurrence of HSVd infecting Japanese plum, cherry plum, and peach in Greece, emphasizing the need for a certification program for the prevention of spreading stone fruit tree viroids in this country. References: (1) K. Amari et al. J. Gen. Virol. 82:953, 2001. (2) N. Astruc et al. Eur. J. Plant Pathol. 102:837, 1996. (3). F. Faggioli et al. Acta. Hort. 550:59, 2001. (4) T. Sano et al. J. Gen. Virol. 70:1311, 1989.

In autumn 2013, fruit of Japanese plum (Prunus salicina) cvs. Angelino and Black Kat developed an unusual brown and soft rot after 2 months in cold storage (0°C) on nearly 1% of the fruit. Fruit showed small, circular, light brown spots that eventually destroyed the entire fruit. Small sporodochia appeared on the fruit surface. Fruit was harvested from orchards located near San Francisco de Mostazal (33°59′ S, 70°41′ W), Chile. Small pieces of diseased tissue were selected from margins of lesions of surface disinfected (96% ethanol) fruit (n = 7) and placed on acidified potato dextrose agar (PDA) plates for 5 days at 20°C. Light brown colonies with even margins and concentric rings of spores were obtained. The conidia of five isolates were one-celled, hyaline, lemon-shaped, (min. 10.7) 14.9 ± 1.5 (max. 18.6) × (min. 8.1) 9.4 ± 0.8 (max. 10.8) μm (n = 30), and borne in branched monilioid chains. This fungus was identified as Monilinia fructicola (G. Winter) Honey (1). Identification was confirmed by amplifying and sequencing the ribosomal ITS1-5.8S-ITS2 region using ITS1 and ITS4 primers (3). BLAST analysis of Chilean plum isolates (GenBank Accession Nos. KF148610 and KF148611) were 99 to 100% identical to isolates of M. fructicola originating from the United States (DQ314727 and HQ846966, respectively) and 100% identical to the first Chilean isolate (JN001480) found in nectarines originating from California at the supermarkets in Santiago in June 2009. Koch's postulates were fulfilled by reproducing brown rot symptoms on mature wounded Japanese plums cv. Angelino (n = 8) inoculated with 10 μl of a conidial suspension (105 conidia/ml) or with a mycelium plug (5-mm diameter). After 2 days in humid chambers (>80% relative humidity) at 25°C, all inoculated fruit developed brown rot symptoms with necrotic lesion means of 15.8 and 21.5 mm in diameter in fruit inoculated with conidia and mycelium, respectively. Non-inoculated control fruit remained healthy. Re-isolations were performed on PDA and the presence of M. fructicola was morphologically confirmed in 100% of the symptomatic fruits. To our knowledge, this is the first report demonstrating the presence of M. fructicola causing brown rot in stored Japanese plums in Chile after its first interception in 2009 in Chile, suggesting that this pathogen has been established in the field. Currently, M. fructicola is a quarantine organism under official control, restricted to Prunus orchards between Santiago and Nancagua in central Chile (2). References: (1) EPPO. EPPO Bull. 39:337, 2009. (2) Servicio Agrícola y Ganadero, SAG, Ministerio de Agricultura, Gobierno de Chile. www.sag.cl , accessed 15 November 2013. (3) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al., eds. Academic Press, NY, 1990.

‘SU1 UNIBO’ is a new Japanese plum cultivar developed by the Department of Agricultural Sciences of Bologna University. The original ‘Black Amber’ × ‘Howard Sun’ cross dates to 1994 and was bred by S. Lugli, S. Sansavini, R. Correale, and M. Grandi at the Cadriano Experiment Station under a joint venture with New Plant (formed by Apo Conerpo, Apofruit, and Orogel Fresco) and Bologna University. ‘Black Glamour’ exhibits notably positive growth and fruit traits. It is early bearing, of high and consistent cropping, and picks 20-25 days after ‘Shiro’ in the Bologna area. Its fruit is a high-quality, black skin, yellow-flesh Japanese plum characterized by large fruit size, pronounced firmness and juiciness, good flavour, maintains ripeness on tree for nearly a month for flexible picking, and has good postharvest storability. Bologna University’s knowledge transfer office lodged an EU plant patent application for ‘SU1 UNIBO’ in 2015 and subsequently licenced the commercial rights to New Plant for distribution in Europe.

In six cultivars of European plum (Prunus domestica L.) and six cultivars of Japanese plum (Prunus salicina Lindl.), pollen morphological characteristics: length (L), width (W), length to width (L/W) ratio, and percentage of pollen grains of normal size and shape, small size, and irregular shape were examined using scanning electron microscopy. In addition, pollen germination in vitro was studied using the agar plate method in a medium containing 15% sucrose. It was found that European plum cultivars have larger pollen grains (53.4 μm in length and 28.3 μm in width on average) compared to Japanese plum cultivars (length and width of 41.0 μm and 22.9 μm, respectively). Besides, European plum cultivars had more elongated pollen grains (L/W ratio of 1.88) compared to Japanese plum cultivars (L/W ratio of 1.79). The percentage of pollen grains of normal size and shape was higher in European plum cultivars (69.3%), compared to Japanese plums (51.9%). Similarly, pollen germination in vitro was significantly higher in European plum cultivars (66.2%) compared to Japanese plums (35.6%). A significant correlation was established between the percentage of pollen grains of normal size and shape and pollen germination in vitro (Pearson's correlation coefficients of 0.896 and 0.822 for European and Japanese plums, respectively).

In plants, host factors encoded by susceptibility (S) genes are indispensable for viral infection. Resistance is achieved through the impairment or the absence of those susceptibility factors. Many S genes have been cloned from model and crop species and a majority of them are coding for members of the eukaryotic translation initiation complex, mainly eIF4E, eIF4G and their isoforms. The aim of this study was to investigate the role of those translation initiation factors in susceptibility of stone fruit species to sharka, a viral disease due to Plum pox virus (PPV)., For this purpose, hairpin-inducing silencing constructs based on Prunus persica orthologs were used to generate Prunus salicina (Japanese plum) 4E and 4G silenced plants by Agrobacterium tumefaciens-mediated transformation and challenged with PPV. While down-regulated eIFiso4E transgenic Japanese plums were not regenerated in our conditions, eIFiso4G11-, but not the eIFiso4G10-, silenced plants displayed durable and stable resistance to PPV. We also investigated the alteration of the si- and mi-RNA profiles in transgenic and wild-type Japanese plums upon PPV infection and confirmed that the newly generated small interfering (si) RNAs, which are derived from the engineered inverted repeat construct, are the major contributor of resistance to sharka., Our results indicate that S gene function of the translation initiation complex isoform is conserved in Prunus species. We discuss the possibilities of using RNAi silencing or loss-of-function mutations of the different isoforms of proteins involved in this complex to breed for resistance to sharka in fruit trees.

Prunus is an economically important fruit tree genus and includes many stone fruit trees such as peach (Prunus persica Batsch), apricot, Japanese apricot (Prunus mume), sweet cherry (Prunus avium L.), European plum (Prunus domestica L.), Japanese plum (Prunus salicina Lindl.) and almond [Prunus dulcis (Mill.) D. A. Webb.]. The characterisation of genes associated with agriculturally important traits such as fruit ripening, dormancy, self-incompatibility, fruit quality and various other developmental processes is important to improve Prunus breeding programmes. Based on high-density molecular genetic maps, many genes are located on the genome, and subsequently, most of them were fine-mapped and further identified by positional cloning. Currently, with the availability of the P. mume genome sequence, the identification of new genes is significantly accelerated.

European stone fruit yellows (ESFY) is the most destructive phytoplasmas disease of apricot and Japanese plum in Europe. All conventional preventive defence strategies have been ineffective in the past, however it has been demonstrated that individual plants can recover from the disease, behaving as completely tolerant to ESFY. The status of tolerance seems transmissible by grafting, so investigations about the possibility to transmit this status from visually recovered apricot to Japanese plums in the field, under high ESFY-infection pressure were carried out.

Cherry virus F (CVF) is a tentative member of the genus Fabavirus in the family Secoviridae, consisting of two RNA segments (Koloniuk et al. 2018). To date, CVF has been documented in only sweet cherry (Prunus avium) in the Czech Republic (Koloniuk et al. 2018), Canada, and Greece. In May 2014, we collected leaf samples from four symptomatic (leaf spots and dapple fruits) and two asymptomatic Japanese plum cultivars (Sun and Gadam) grown in an orchard in Hoengseong, South Korea, to identify viruses and viroids infecting plum trees. Total RNA from individual plum trees was extracted using two commercial kits: Fruit-mate for RNA Purification Kit (Takara, Shiga, Japan) and RNeasy Plant Mini Kit (Qiagen, Hilden, Germany). We generated six mRNA libraries from the six different plum cultivars for RNA-sequencing using the TruSeq RNA Library Preparation Kit v2 (Illumina, CA, U.S.A.) as described previously (Jo et al. 2017). The mRNA libraries were paired-end (2 X 100 bp) sequenced with a HiSeq 2000 system (Macrogen, Seoul, Korea). The raw sequence reads were de novo assembled by Trinity program v. 2.8.6, with default parameters (Haas et al. 2013). The assembled contigs were subjected to BLASTX search against the non-redundant protein database in NCBI. Of the two asymptomatic cultivars, the transcriptome of asymptomatic plum cv. Gadam contained five contigs specific to CVF. Two and three contigs were specific to CVF RNA1 (2,571 reads, coverage 42.15%) and RNA2 (2,025 reads, coverage 53.04%), respectively. The size of these five contigs ranged from 241 to 5,986 bp. Contigs of 5,986 and 3,867 bp in length, referred to as CVF isolate Gadam RNA1 (GenBank MN896996) and RNA2 (GenBank MN896995), respectively, were subjected to BLASTP search against NCBI's non-redundant protein database. The results showed that the polyprotein sequences of RNA1 and RNA2 shared 95.3% and 93.11% amino acid identities with isolates SwC-H_1a from the Czech Republic (GenBank acc. no. AWB36326) and Stac-3B_c8 from Canada (AZZ10055), respectively. To confirm the infection of CVF in cv. Gadam, RT-PCR was conducted using CVF RNA1-specific primers designed based on the CVF reference genome sequences (MH998210 and MH998216), including 5'-CCACCAAATAGGCAAGAGGTCAC-3' (position 3190-3212) and 5'-CACAATCACCATCAATGGTCTCTGC-3' (position 3742-3766), and CVF RNA2-specific primers, including 5'-CTGCTTTATGATGCTAGACATCAAGATG-3' (position 1015-1042) and 5'-ACAATAGGCATGCTCATCTCAACCTC-3' (position 1594-1619). We amplified 577-bp RNA1-specific and 605-bp RNA2-specific amplicons that were cloned and then performed Sanger sequencing. Sequencing of the cloned amplicons for isolate Gadam RNA1 (GenBank MN896993) and RNA2 (GenBank MN896994) revealed values of 99.48% and 99.17% nucleotide identity to that of RNA1 and RNA2 determined by high-throughput sequencing, respectively. Additionally, we tested five plants for each of the six plum cultivars grown in the same orchard. The detection of CVF was carried out through PCR using the primers and protocol described above. Of the 30 trees, CVF was detected in three trees of cv. Gadam by both primer pairs. To our knowledge, this is the first report of CVF infecting Japanese plum and the first report of the virus in Korea. However, its prevalence in other Prunus species, including apricot, European plum, and peach, should be further elucidated.

Plum (Prunus domestica L., Rosaceae) trees, like many stone fruit trees, are known to be infected by numerous plant viruses, predominantly as consequence of their clonal mode of propagation and perennial cultivation (Jelkmann and Eastwell, 2011). Apricot vein clearing-associated virus (AVCaV) is a member of the genus Prunevirus in the family Betaflexiviridae. AVCaV was first reported in Italy infecting apricot (P. armeniaca L.) associated with foliar vein clearing symptoms (Elbeaino et al. 2014). It has also been detected in various Prunus species, like plum, Japanese plum (P. salicina L.), sour cherry (P. cerasus L.), and Japanese apricot (P. mume L.), apricot and peach (P. persica L.) sourced from Asian and European countries (Marais et al. 2015), as well as in the ornamental Myrobolan plum (P. cerasifera L.) in Australia (Kinoti et al. 2017). In 2018, during the vegetative season, a survey was carried out in two different apricot and plum orchards in the southern region of Agdez (Agadir, Morocco) where stone fruit trees are grown. Five branches with leaves were sampled from three apricot and three plum trees of unknown cultivars, all asymptomatic. Total RNA was extracted from 100 mg plant tissue (leaves and cambial scrapping) using RNeasy Plant Mini Kit (QIAGEN, Hilden, Germany) and separate samples (one per species) were used for library preparation (NEBNext Ultra RNA library kit; New England BioLabs, MA, USA), and sequencing (Illumina NextSeq v2, totRNA sequencing) at Admera Health (New Jersey, USA). All generated reads (6,756,881) from the plum sample were quality filtered and submitted to the VirusDetect pipeline (Zheng et al., 2017). The plum cDNA library, a total of 20 viral contigs (68-1928 bp) mapped to several AVCaV accessions in GenBank. A reference mapping (CLC Genomics Workbench 12, Qiagen, Denmark) was conducted against all four available AVCaV full genomes (KM507062-63, KY132099 and HG008921), revealing 100% coverage of the full sequence (8358 nt) with 97-98 % nucleotide (nt) identities (BLASTn). Analysis of the derived sequences allowed to identify the location of the four predicted ORFs i.e. (ORF1: 6066 nt/2,021 aa), (ORF2: 1383 nt/460 aa), (ORF3: 666 nt/221 aa) and (ORF4: 420 nt/139 aa), previously described for the AVCaV genome (Elbeaino et al. 2014). The amino acid sequences of the encoded proteins of AVCaV isolate from Morocco also shared 97-98% identities with the corresponding sequences of complete genome AVCaV isolates in GenBank. To confirm the detection of AVCaV in the three plum samples, specific RT-PCR primers (VC37657s: 5'-CCATAGCCACCCTTTTTCAA-3' / VC28239a: 5'-GTCGTCAAGGGTCCAGTGAT-3') (Elbeaino et al. 2014) were used and the expected 330 bp fragment from the replicase gene was amplified in all three samples and subsequently sequenced (MT980794-96). Sanger sequences were 100% identical to corresponding HTS derived sequence. This is the first report of AVCaV infecting plum in Africa. The incidence of AVCaV in Moroccan Prunus species is unknown. Plum trees from the surveyed orchards were also confirmed to be co-infected with little cherry virus 1 (LChV-1) using HTS. Further investigation is required to determine the impact of AVCaV on these asymptomatic plum trees and other stone fruits species.

During a survey in May 2020, symptoms of blight were observed on apricot (Prunus armeniaca cv. undetermined) in an orchard (37°06´01.5″N 127°57´44.9″E) in Chungju, South Korea, where fire blight of apple occurred. Three apricot trees in the apple orchard were heavily diseased and showed severe shoot blight and stem canker symptoms. Bacterial isolates were recovered on King's medium B from leaves and twigs that were surface-sterilized with 70% alcohol. Colonies with uniform mucoid, smooth surfaces were collected. DNA from nine isolates did not yield an amplicon in a PCR assay for detection of Erwinia pyrifoliae using primer set CPS1/CPS2c (Kim et al. 2001). Each isolate was positive in PCR assays for E. amylovora using primer sets A/B (Bereswill et al. 1992) and AJ75/76 (Llop et al. 2000) that target pEA29. Sequencing of the PCR products resulted in 99.9% (929 bp out of 930 bp) and 100% (747 bp out of 747 bp) identity with sequences of E. amylovora FB20 (GeneBank: CP050240), respectively. Amplifications of the partial 16S rRNA (GeneBank: LC557153) and hrpN (GeneBank: LC575997) genes were performed, and the products were sequenced. The primers used to amplify 16S rRNA were 518F: 5'-CCAGCAGCCGCGGTAATACG-3' and 800R: 5'-TACCAGGGTATCTAATCC-3', and those for the hrpN genes were HRPN1: 5'-ATGAGTCTGAATACAAG-3' and HRPN3c: 5'-GCTTGCCAAGTGCCATA-3'. BLAST analyses showed 99.8% (1439 bp out of 1442 bp) and 100% (1136 bp out of 1136 bp) identities, respectively, to the sequences of E. amylovora FB20. The ability of the isolates to induce a hypersensitive reaction on tobacco (Nicotiana tabacum cv. Xanthi) leaves was also evaluated. Bacterial suspensions (1.5 ⅹ 108 CFU) of 2 isolates were injected into tobacco leaves, and after 48 h, both isolates caused a hypersensitive response. To confirm pathogenicity of isolates, 3-mm-deep holes in five immature apricot (cv. Goldcot) and five immature apple (cv. Fuji) fruits were inoculated with 10 µl bacterial suspension (1.5 ⅹ 108 CFU/ml). The inoculated fruits were placed in a humid plastic box. After 7 days at 27℃, severe necrosis and bacterial ooze were present at the inoculated sites in three repeated tests. No symptoms were observed on fruits inoculated with sterile water. To complete Koch's postulates, bacteria were reisolated from the inoculated apricot and apple fruits. PCR using the specific primer sets stated above confirmed the identity as E. amylovora. Thus, based on disease symptoms, sequences, and pathogenicity, the bacterium causing blight of apricot was identified as E. amylovora. Natural infections of E. amylovora on apricot trees have been reported in the Czech Republic and Hungary (Korba and Sillerova 2011; Vegh and Palkovics 2013). Fire blight was observed in the Czech Republic on apricot trees near pear seedlings, which are highly susceptible to E. amylovora (Korba and Sillerova 2011). Natural infections of E. amylovora on Japanese plum planted adjacent to an apple orchard with severe fire blight has been reported in the United States (Mohan and Thomson 1996). Moreover, susceptibility to fire blight has been reported for apricot and Japanese plum cultivars (Mohan and Bijman 1999). To our knowledge, this the first report of fire blight of apricot caused by E. amylovora in Korea. This report is important because it provides evidence that apricot may be an overlooked reservoir for E. amylovora, in addition to apple, pear, and other rosaceous plants, in Korea. An intensive survey for additional host plants for the fire blight pathogen will be continued in Korea. This work was supported by a grant from the Agenda program (PJ01530202) of Rural Development Administration, Republic of Korea.

Most Japanese plum cultivars are self-infertile. In commercial orchards, cross-compatible pollinisers have to be interplanted to ensure fruit set. The self-incompatibility is controlled by S-loci in the pistil and pollen, which are tightly linked to each other. The Prunus S-RNase-specific PCR primers Pru-C2 and PCE-R were used to study candidate compatible pollinisers for the cultivar 'Queen Garnet', known for its high nutritional value. A total of 13 genotypes, including 'Queen Garnet', three other cultivars and nine DAFF breeding lines, were tested. 'Queen Garnet', which possesses gh S-haplotypes, shares none or only one S-haplotype with the other three cultivars and five of the DAFF breeding lines. Not only must an ideal polliniser be cross-compatible in terms of S-haplotype, but it must also overlap in flowering with the main cultivar and produce sufficient quantities of viable pollen. Based on these three criteria, lines ARF25, ARF86, ARF95 and ARF98 were identified for interplanting one row in five to ensure pollination each year and for ease of harvesting. Implementation of this pollination strategy coincided with a 50-fold increase in 'Queen Garnet' fruit yield between 2012-2013 and 2013-2014. While this increase may be partially due to tree maturity and environmental conditions, there is an expectation of up to another 13-fold increase in the following years as trees develop and mature within this improved pollination environment.

Tarn Hoa plum is one of three hybrids of the Japanese plum (Prunus salicina), originating from southern China, and grown between 700 and 1000 m altitude in north-west Vietnam for the domestic market. Along with some leguminous crops grown in rotation with maize, plums are an important source of additional income for smallholders. The aim of the project was to develop competitive value chains for plums with high levels of smallholder engagement. The research design was both structured and adaptive, based on participative action research. In addition, sensory evaluation to determine optimum measurable indicators of ripeness (soluble solids and hardness) based on consumer preferences was conducted to adjust time of harvesting. The research found that Tarn Hoa plum production and marketing is a large, complex system that is interconnected with the marketing of green (immature) plums to China and other substitutable fruit such as lychees, longans and other plums. It is a highly opportunistic, low-input system the outputs of which depend on plum prices, the relative production capability of districts and local microclimates. The 40- to 45-day plum harvest season is highly variable regarding harvesting dates, harvest duration, plum quality and, consequently, market prices. It was established that there is sufficient profit margin for all chain participants to establish a sustainable niche value chain based on high-quality sweet plums if reliable and sufficient throughput can be achieved. It is recommended that future similar value chain projects pay particular attention to selecting large 'aggregators' and 'distributors' so as to achieve volume and stable market access.

Introduction. Plum cultivars exhibit differences in their fruit quality; however, very little is known about the changes in fruit growth and quality of plum cultivars maturing in different seasons. This study was conducted to contribute to a better understanding of the fruit growth and ripening behavior of Japanese plum (Prunus silicina Lindl.) varieties according to their maturing season. Materials and methods. Three Japanese plum cultivars were studied: early- [‘Black Amber’ (BA)], mid- [‘Amber Jewel’ (AJ)] and late-season [‘Angelino’ (AG)] maturing. The increase in fruit weight and diameter was determined from days after full bloom (DAFB) to harvest, whilst changes in fruit pulp, skin and seed dry weights, fruit firmness, soluble solid contents (SSC), and titratable acidity (TA) were studied during days after stone hardening (DASH). Ethylene production, respiration rate, activities of 1-aminocyclopropane-1-carboxylic acid synthase (ACS) and 1-aminocyclopropane-1-carboxylic acid oxidase (ACO) enzymes, fruit firmness, fruit color, SSC, TA, ascorbic acid, total antioxidant and carotenoid contents were determined at alternate days during fruit ripening. Results and discussion. All plum cultivars exhibited three distinct phases of fruit growth and development in the DAFB. The AG fruit exhibited the longest duration of phase-III, about 64 days and 12 days more, as compared with BA and AJ fruits, respectively. Fruit skin dry weight (%) was higher for AG fruit, whilst, AJ and BA fruits exhibited the highest increase in seed and pulp dry weight (%) during DASH. The BA and AJ fruits showed climacteric fruit ripening with a sharp rise in ACS and ACO enzymes; whereas AG fruit showed suppressed climacteric ripening. During the fruit ripening period AG fruit remained more firm with higher SSC, and SCC:TA ratio as compared with BA and AJ fruits. The level of ascorbic acid (24.8 mg 100 g-1 ) was higher in AG fruit. Whilst, total carotenoids (0.66 mg 100 g-1 ) and total antioxidants (215 ¯mol Trolox 100 g-1 ) were higher in AJ and BA fruit respectively. Conclusion. The physico-chemical changes during fruit ripening vary with cultivar and are associated with the level of endogenous ethylene production. Japanese plum cultivars exhibit varying levels of SSC, SSC:TA ratio, levels of individual and total antioxidants of their ripe fruits.

Fibre microparticles (MPCs) obtained from Japanese plum (Prunus salicina) skin and flesh through ethanolic extraction retained polyphenolic compounds, mainly proanthocyanidins, in 170–200 mg/100 g MPCs levels. Also, phenolics such as anthocyanins (cyanidin 3-galactoside and 3-rutinoside), responsible for red-purple colour, and flavonoids (quercetin derivatives), were found in significant proportions only in the skin MPCs. The MPCs-polyphenolic extract showed antioxidant capability (DPPH and FRAP assays) as well as protective effect against the oxidative stress induced by tert-butylhydroperoxide (t-BOOH) when biologically evaluated on kidney cells, joined to a low cytotoxicity (50%-cytotoxic concentration >100 µg/mL). This is important since health benefits of barely absorbed proanthocyanidins rest on their permanence into the intestine, interfering with oxidative stress implicated in inflammatory disorders. Higher proportions of pectins found in flesh MPCs and of lignin in skin MPCs can provide different fibre functionality. Plum MPCs obtained can be useful as antioxidant natural additives and ingredients for functional food preservation.

Flavonoids are responsible of different fruit sensorial properties. In Japanese plum (Prunus salicina L.) these compounds are variable in both type and quantity during the different stages of fruit growth and maturation. Here we present the first study which determines the expression profile of structural genes of the flavonoid pathway and accumulation profiles of total phenols, proanthocyanidins and anthocyanins during fruit development stages in contrasting cultivars in Japanese plum. The biosynthesis of these compounds is differentially regulated in different tissues and cultivars. Our result showed that all pigmented tissues increased the expression of the leucoanthocyanidin dioxygenase (LDOX) gene, while all tissues without anthocyanin accumulation presented a minimal expression of LDOX. In addition, the regulation of putative transcription factors PsMYB10 and PsMYB1 were correlated positively and negatively with the pigmented tissues respectively, suggesting a critical and coordinated mechanism involved in the change of the fruit color.

Virus-induced gene silencing (VIGS) has been used as a rapid and effective tool for functional analysis of genes in various plants, including woody fruit tree species. We previously reported the successful induction of VIGS of the endogenous PHYTOENE DESATURASE ( PDS ) gene in apricot ( Prunus armeniaca L.) using Apple latent spherical virus (ALSV) vectors. In contrast, our attempts to infect Japanese apricot ( Prunus mume Siebold & Zucc.) with ALSV vectors was unsuccessful, suggesting that species- and/or cultivar-dependent differences of ALSV susceptibility may exist in Prunus . In this study, we investigated whether this VIGS-based gene evaluation system using ALSV vectors was applicable to seven Prunus species, including apricot, sweet cherry ( Prunus avium L.), almond [ Prunus dulcis (Mill.) D. A. Webb.], peach ( Prunus persica Batsch), Japanese apricot, Japanese plum ( Prunus salicina Lindl.), and European plum ( Prunus domestica L.). ALSV vectors carrying part of the apricot PDS gene sequence were amplified in Nicotiana benthamiana , and inoculated into the cotyledons of Prunus seedlings by particle bombardment. Typical PDS -silenced phenotypes, characterized by uniform discoloration of the upper leaves, were observed in sweet cherry and some cultivars of apricot and almond several weeks after inoculation. The amounts of PDS mRNA in the infected leaves were significantly reduced, while a 21 nt antisense small RNA, which was assumed to play a central role as a guide RNA in PDS mRNA degradation, was highly accumulated. However, ALSV infection of Japanese apricot, Japanese plum, European plum, and the other cultivars of apricot and almond was unsuccessful. Furthermore, although the infection rate of ALSV in peach was high, severe pale spots (a viral infection symptom) were observed in the infected leaves. These results collectively suggested that the efficiency of ALSV infection and VIGS could vary depending on species and/or cultivar in Prunus . The possible use of the ALSV-mediated VIGS system for functional analysis of genes in Prunus is discussed.

Japanese plums are popular fruits since they are exceptionally nutritious with high fiber and antioxidant content. This work has aimed to analyze the most critical phenology, fruit quality and postharvest parameters from a genomic point of view to identify molecular markers closely linked to the most significant Quantitative trait loci (QTLs). A genetic linkage map of an F1 population of 151 individuals from the cross '98–99’ × 'Angeleno' was constructed using previously reported Single Nucleotide polymorphism (SNP) data and 25 additional Simple Sequence Repeat (SSR) markers. Twenty-three phenotypic traits evaluated during three harvest seasons were assayed to estimate best linear unbiased predictors by using two genomic association QTL analysis approaches: General Linear Model-based single marker-trait associations (GLM) and Multiple QTL Model analyses (MQM). In addition, loss of weight and chlorophyll degradation between days 1 and 7 as well as fruit softening for days 1, 4, and 7 were monitored during two consecutive seasons. The most significant identified QTLs were linked to fruit development period and fruit weight in Linkage Groups (LG) 4 and 2, respectively. Regarding postharvest parameters, the identified QTLs related to chlorophyll degradation and loss of weight showed lower significance than phenology or fruit quality traits. In contrast, minor QTLs for fruit firmness evolution using destructive and non-destructive methods were confirmed in LG 4 and 5.

In India as well as in other significant regions of the world, plum production is focussed on a very small pool of varieties that inhibits its expansion and limits the availability of fruits all year round. This situation emphasizes on the urgent requirement of evolving alternative cultivars of rootstock and scion, with better performance under local situation and contrasting spacing. Japanese plum cultivar ‘Satluj Purple’ (Fla 1–2) is known for its hardy nature, precocity, high productivity and regularity in bearing appropriate for both the juice manufacturing industry and fresh fruit marketplace. In spite of having good fruit quality under sub–tropical scenario and early market availability when other fruits are not accessible, only a few rootstock studies for ‘Satluj Purple’ have been executed in India. Consequently, a field study was conducted at Punjab Agricultural University, Ludhiana state, to assess the horticultural output of ‘Satluj Purple’ Japanese plum grafted on four rootstocks: ‘Kala Amritsari’ (Prunus salicina L.), ‘Kabul Green Gage’ (Prunus salicina L.), Sharbati (Prunus persica Batsch) and Flordaguard (Prunus persica Batsch) over two consecutive seasons. The experimental grove was planted in 2015 using a 6 × 6 m and 6 × 1.5 m spacing, in a randomized block design, with three replications and two trees per replication under climate conditions typical of a semi–arid and sub–tropical area. Fruiting, yield and fruit quality were assessed for each rootstock at different spacing. Reproductive growth (fruit set, fruit retention and fruit yield per tree) was found to be higher on ‘Kala Amritsari’ rootstock. Fruits harvested from trees grafted on ‘Kala Amritsari’ were superior in fruit quality (fruit weight, fruit colour, total soluble solids (TSS), titratable acidity (TA) and ripening index (TSS/TA). Irrespective of the rootstocks, the performance of plum trees in terms of fruiting, yield and fruit quality was better in 6 × 6 m planted trees as compared to trees planted at 6 × 1.5 m distances. Yield was found to be positively correlated with fruit weight, chroma, TSS, ripening index, fruit set and retention while it was negatively correlated with the TA values. Overall, the results from this study indicated that the rootstocks ‘Kala Amritsari’ and ‘Kabul Green Gage’ are the most suitable rootstocks for ‘Satluj Purple’ under the conditions investigated herein. Finally, the ‘Satluj Purple’ trees at spacing of 6 × 6 m performed better as compared to 6 × 1.5 m planted trees regardless of the rootstocks.

In stone fruits, the pit hardening period is usually one of slow fruit growth that is considered relatively insensitive to an imposed moderate water stress. For this reason, this period is commonly employed for a first phase of reduced water input in regulated deficit irrigation (RDI) strategies. However, in previous studies with the Japanese plum cv. 'Angeleno', the identification of a period of slow growth just before harvest suggested the need to reconsider the most suitable RDI strategy for this cultivar. In this 3-year study (2014, 2015 and 2016) three irrigation strategies were compared: Control (CON) designed to meet tree water requirements throughout the season; Regulated Deficit Irrigation (RDI) with two separate periods of water deficit, one preharvest with no irrigation inputs during an intermediate period of fruit growth (pit hardening period), and the other postharvest with a 30 % reduction of the CON inputs; and Preharvest + Regulated Deficit Irrigation (RDP) with a single period of deficit irrigation initiated before harvesting and extended until the end of the irrigation campaign. Both deficit irrigation treatments were found to be effective at controlling tree vigor, with lower trunk cross-sectional area growth and pruned wood weight than in the CON treatment. Average water savings with the RDI and RDP strategies over the three years of the study were 24 % and 18 %, respectively, compared to CON, with no impact on yield and no carry-over effect. Fruit size in the RDP treatment was similar to the CON. The differences in fruit firmness, soluble solids concentration (SSC), acidity, lightness (L), hue (ho) and chroma (C*) of the skin were only slight or inconsistent over the three years. Our results confirm the suitability of moderate pre- and postharvest water stress (RDP strategy) in this cultivar, with greater water productivity than the traditional RDI strategy., This research was supported by the National Institute for Agricultural and Food Research and Technology (INIA) [RTA2012-00034-C02-02] of the Ministry of Economy and Competitiveness of the Spanish Government and [CCESAGROS] by European Regional Development Fund and the Government of Extremadura. Fernando Blanco Cipollone received a PhD scholarship (CPR—2014-0148) from INIA.

Prunus salicina L., commonly called Chinese plum or Japanese plum, is a small deciduous tree native to China and widely distributed in the world. Since spring of 2018, an unknown disease has affected commercial plums grown in an orchard located in Dazhou, Sichuan Province, China (31°40′41″N, 107°43′57″E). Disease symptoms in plum trees include water-soaked lesions on immature fruits, brown necrotic spots, and holes with a yellow halo in leaves, as well as dark brown oily cankers on twigs. To isolate the causal agent, surface-disinfested tissues from three separate symptomatic fruits, leaves, and twigs were placed onto nutrient agar (NA) plates and were incubated at 28°C. Pale yellow colonies with smooth margins and mucoid texture appeared after 12 h of incubation. Individual colonies were transferred two times to NA plates using the conventional streak plate techniques to obtain pure cultures. Purified bacteria cells were rod shaped, 1.5 to 3.0 μm long, and 0.5 to 1.0 μm wide. Three isolates (named CdjP1, CdjP2, and CdjP3) were used for further characterization. Biochemical tests using Gram stain, MacConkey agar, and Kovacs’s indole kit (Solarbio, Beijing, China) indicated that the three isolates were gram negative, lactose positive, and indole negative. The 16s rDNA fragment was amplified for the three strains using universal primers 27F and 1492R (Lane 1991) and sequenced (GenBank accession nos. MN542182, MN542183, and MN542184). BLASTn analysis revealed the nearly full-length (about 1,400 bp) 16S rDNA sequences of CdjP1, CdjP2, and CdjP3 shared over 99% identity with Pantoea agglomerans (MH101508) (identities 1,400/1,406, 1,407/1,412, 1,405/1,413), P. vagans (CP038853) (identities 1,397/1,406, 1,403/1,412, 1,402/1,414), and P. ananatis (KC178592) (identities 1,399/1,406, 1,405/1,412, 1,404/1,414), respectively. Multilocus sequence analysis has been shown to be a powerful molecular method for delineation of Pantoea species (Deletoile et al. 2009; Tambong et al. 2014). To identify the species of CdjP1, CdjP2, and CdjP3, six housekeeping genes (fusA, gyrB, leuS, pyrG, rlpB, and rpoB) of each strain were amplified and sequenced (GenBank accession nos. MN549363 to MN549380). Then a phylogenetic tree was constructed using Bayes inference methods based on fusA-gyrB-leuS-pyrG-rlpB-rpoB concatenated fragments (2,997 bp), which showed that CdjP1, CdjP2, and CdjP3 are most closely related to P. agglomerans. To fulfill Koch’s postulates, pathogenicity tests were conducted on 3-year-old plum trees (cv. Qinba) grown in Sichuan Province, China (31°40′53″N, 107°44′2″E). Immature plum fruits, leaves, and twigs were wounded with a sterile toothpick and were inoculated with 20 µl of bacterial suspension (10⁸ CFU/ml) of each isolate. Plants inoculated with sterile water were used as a control. All treatments and the control were repeated three times. The trees were then grown under natural conditions (monthly mean maximum temperature 32°C, monthly mean minimum temperature 23°C). After 2 weeks, all test-isolate-inoculated plum fruits, leaves, and twigs developed symptoms similar to those of the natural infections observed. No lesions were observed on the controls. Bacteria reisolated from the infected plum fruits, leaves, and twigs were similar in colony appearance to the original isolates, and the 16s rDNA fragments were identical to their original isolate sequences, thereby fulfilling Koch’s postulates. Based on colony morphology, biochemical tests, 16S rRNA gene sequencing data, and phylogenetic analysis, the pathogen was identified as P. agglomerans. In China, P. agglomerans has been reported to infect cotton, walnut, Vigna angularis, and Ziziphus jujuba (Lu et al. 2015; Ren et al. 2008; She et al. 2019; Yang et al. 2011). To our knowledge, this is the first report of P. agglomerans causing bacterial necrosis of plum in China or worldwide. This report expands the host range of P. agglomerans and will help to develop effective disease control strategies, as the etiology is known.

The effects of climate change have forced to search quickly new strategies to achieve sustainable agriculture in the context of a growing demand for food. Rootstocks have shown to have a key role in the resistance and tolerance to biotic and abiotic stresses in horticultural and fruit trees species, being a way to incorporate these strengths to the cultivated varieties. Here, we report the assessment of physiological parameters and growth responses of two commercial interspecific hybrid Prunus rootstocks contrasting in their tolerance to water deficit: ‘ROOTPAC®40’ (tolerant) and ‘ROOTPAC®20’ (sensitive); grafted with the almond cultivar Non Pareil or the Japanese plum cultivar Angeleno. Plants were subjected during 35 days to two irrigation treatments, well-watered and water deficit (drought period), followed by a recovery period of 44 days. On each period, biomass accumulation, stomatal density, water-use efficiency at the whole plant level and root hydraulic conductivity were determined in both irrigation treatments. Also, in the drought period, the fraction of transpirable soil water when the relative transpiration drops and the expression of seven aquaporins belonging to plasma membrane intrinsic proteins subfamily was assessed. In the drought period, ‘ROOTPAC®20’ had a decrease in the aquaporin gene expression in roots and also had an early decline in transpiration, independent of the grafted scion. Also, on this rootstock, the biomass was more severely affected. On the other hand, ‘ROOTPAC®40’ induced a late decline in transpiration and increased the water-use efficiency, keeping less affected the biomass accumulation. Contrasting with the above, in the recovery period, ‘ROOTPAC®20’ improved the water-use efficiency, reaching higher biomass accumulation in the grafted plants. Also, we observed some interesting interactions between rootstocks and scions. ‘ROOTPAC®20’ induced a higher stomatal density in both, almond and plum scions, and ‘Angeleno’ plum induced a bigger root hydraulic conductivity in both rootstocks, in comparison to almond ‘Non Pareil’, in the drought period.

Japanese plum (Prunus salicina Lindl.) exhibits gametophytic self-incompatibility, a prezygotic reproductive barrier that inhibits the growth of self-pollen tubes in the style, preventing self-fertilization. This reaction of incompatibility is genetically controlled by a multiallelic locus (S). When the S allele in the pollen grain is the same as either of the two S alleles expressed in the pistil, the pollen tube arrests its growth in the style preventing fertilization. Most Japanese plum-type cultivars are self-incompatible and need cross-pollination with compatible cultivars coincident at flowering. In the last years, an important renewal of plant material is taking place, with the introduction of a number of new cultivars from breeding programs of different countries whose objectives include self-compatibility. In South Africa, the ARC Infruitec/Nietvoorbij program has released a series of new cultivars that are being introduced in the main producing countries. However, their adaptability to other areas with different climatic conditions is unknown. In this work, the pollination requirements of twelve cultivars from ARC-Infruitec program is determined, analyzing their behavior in Extremadura (Spain), one of the main producing areas in Europe. For this purpose, for each cultivar, pollen viability has been evaluated through in vitro pollen germination, self(in)compatibility has been determined by the observation of pollen tube growth in self-pollinated flowers under the microscope, and S-alleles have been identified by PCR analysis. The time of flowering has been monitored over five years. The selection of adequate pollinizers were done by assigning the cultivars to their corresponding incompatibility group and comparing their time of flowering. These results can be extrapolated to other areas where these cultivars are newly introduced, although additional data of flowering dates may be required for each zone.