Japanese Plum Cultivars Research Articles

Evaluation of different deficit irrigation strategies in the late-maturing Japanese plum cultivar 'Angeleno'

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.

Rootstocks modulate the physiology and growth responses to water deficit and long-term recovery in grafted stone fruit trees

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.

Using Soil Moisture Sensors for Automated Irrigation Scheduling in a Plum Crop

The growing scarcity and competition for water resources requires the urgent implementation of measures to ensure their rational use. Farmers need affordable irrigation tools that allow them to take advantage of scientific know-how to improve water use efficiency in their common irrigation practices. The aim of this study is to test under field conditions, and adjust where required, an automated irrigation system that allows the establishment of regulated deficit irrigation (RDI) strategies in a stone fruit orchard. For this, an automated device with an algorithm which combines water-balance-based irrigation scheduling with a feedback adjustment mechanism using 15 capacitive sensors for continuous soil moisture measurement was used. The tests were carried out in 2016 and 2017 in Vegas Bajas del Guadiana (Extremadura, Spain) on an experimental plot of ‘Red Beaut’, an early-maturing Japanese plum cultivar. Three irrigation treatments were established: control, RDI and automatic. The control treatment was scheduled to cover crop water needs, a postharvest deficit irrigation (40% crop evapotranspiration (ETc)) strategy was applied in the RDI treatment, while the Automatic treatment simulated the RDI but without human intervention. After two years of testing, the automated system was able to “simulate” the irrigation scheduling programmed by a human expert without the need for human intervention.

Morphological characteristics and germination of pollen in European and Japanese plum cultivars

Morphological characteristics and germination of pollen in European and Japanese plum cultivars

Differences and similarities between some European and Japanese plum cultivars

Differences and similarities between some European and Japanese plum cultivars

Rosehip oil coating delays postharvest ripening and maintains quality of European and Japanese plum cultivars

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.

Phenotypical characterization and molecular fingerprinting of natural early-flowering mutants in apricot (Prunus armeniaca L.) and Japanese plum (P. salicina Lindl.)

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 Pasión Precoz’ and ‘Búlida 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.

Quantification of lenticels in Japanese plum cultivars and their effect on total fruit peel permeance

Fruit peel vapour permeance is an indicator of the propensity of fruit to lose moisture. Permeance is affected by cuticle composition, as well as stomata, lenticels and cracks in the cuticle. Stomata play a significant role in controlling the transpiration of leaves. Since lenticels on fruit often form from non-functional stomata, this study determined whether lenticels contribute to peel permeability in Japanese plums and whether this varies between cultivars. In 2015/16 as well as 2016/17, ‘Laetitia’ and ‘Songold’ were investigated and in 2016/17, ‘African Delight™’ and ‘Sapphire’ were added to the study. Fruit were sampled from three weeks before commercial harvest until the commercial harvest date. On each sampling date, the peel permeability of individual fruit was determined and the number of open lenticels quantified. Lenticel numbers and peel permeability of fruit both differed significantly between fruit of different cultivars and between seasons. Significant correlations between permeability and the number of open lenticels were found only in ‘Songold’, ‘African Delight™’, and ‘Sapphire’ fruit. The percentage of open lenticels are therefore not the determining factor of total fruit peel permeability or the tendency of plums to lose moisture. Cuticle composition seems to play a more important role in determining fruit moisture loss.

Ethylene Response of Plum ACC Synthase 1 (ACS1) Promoter is Mediated through the Binding Site of Abscisic Acid Insensitive 5 (ABI5).

The enzyme 1-amino-cyclopropane-1-carboxylic acid synthase (ACS) participates in the ethylene biosynthesis pathways and it is tightly regulated transcriptionally and post-translationally. Notwithstanding its major role in climacteric fruit ripening, the transcriptional regulation of ACS during ripening is not fully understood. We studied fruit ripening in two Japanese plum cultivars, the climacteric Santa Rosa (SR) and its non-climacteric bud sport mutant, Sweet Miriam (SM). As the two cultivars show considerable difference in ACS expression, they provide a good system for the study of the transcriptional regulation of the gene. To investigate the differential transcriptional regulation of ACS1 genes in the SR and SM, their promoter regions, which showed only minor sequence differences, were isolated and used to identify the binding of transcription factors interacting with specific ACS1 cis-acting elements. Three transcription factors (TFs), abscisic acid-insensitive 5 (ABI5), GLABRA 2 (GL2), and TCP2, showed specific binding to the ACS1 promoter. Synthetic DNA fragments containing multiple cis-acting elements of these TFs fused to β-glucuronidase (GUS), showed the ABI5 binding site mediated ethylene and abscisic acid (ABA) responses of the promoter. While TCP2 and GL2 showed constant and similar expression levels in SM and SR fruit during ripening, ABI5 expression in SM fruits was lower than in SR fruits during advanced fruit ripening states. Overall, the work demonstrates the complex transcriptional regulation of ACS1.

Reproductive behaviour of new South African cultivars of Japanese plum

Reproductive behaviour of new South African cultivars of Japanese plum

Floral biology of some European and Japanese plum cultivars for phenological properties grown under temperate conditions of Kashmir

The studies on the floral biology of some European and Japanese plum cultivars for phenological characteristics were conducted in Sher-e-Kashmir University of Agricultural Sciences and Technology, Srinagar, Kashmir during the year 2016–17. The present study consisted of six plum cultivars viz. Burbank, Stanley, Friar, Wickson, Santa Rosa and Satsuma of uniform age replicated thrice in a Randomized Complete Block Design (RCBD). In the experimental year, swollen bud, bud burst, green cluster, white bud, initial bloom, full bloom, blooming period and petal fall were determined in terms of days after reference date (DARD). The data recorded revealed that the swollen bud and bud burst stage was recorded first in cultivar Satsuma (22.66 DARD and 28.33 DARD) which was statistically at par with Friar (22.67 DARD and 28.57 DARD) and late in cultivar Stanley (33.00 DARD and 51.67 DARD) respectively. The green cluster stage was observed earliest in cultivar Friar (40.33 DARD), while the earliest white bud stage was recorded in cultivar Satsuma (51.67 DARD). The initial bloom (54.23 DARD) and full bloom (59.53 DARD) was recorded earliest in cultivar Friar which was statistically at par with Satsuma, while as late green cluster (57.20 DARD), white bud (68.33 DARD), initial bloom (72.43 DARD) and full bloom (75.43 DARD) stage was recorded in cultivar Stanley. The petal fall was found earliest in cultivar Satsuma (67.23 DARD) and late in cultivar Stanley (80.23 DARD) respectively. The study concluded on the note that cultivars Satsuma and Friar were earliest to bloom and Stanley was late to bloom.

Development and applicability of GBS approach for genomic studies in Japanese plum (Prunus salicina Lindl.)

ABSTRACTGenotyping 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.

Hormone balance in a climacteric plum fruit and its non-climacteric bud mutant during ripening

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.

Long-term graft compatibility study of peach-almond hybrid and plum based rootstocks budded with European and Japanese plums

The introduction of some new rootstocks requires knowledge of the potential ‘translocated’ and ‘localized’ graft incompatibilities before releasing these rootstocks into the market. Trials were established at the Aula Dei Experimental Station (Zaragoza, Spain) to assess graft compatibility between five European plum (Prunus domestica L.) and six Japanese plum (Prunus salicina L.) cultivars with thirty-eight rootstocks belonging to peach × almond hybrids, as well as slow-growing, fast-growing and interspecific hybrid plum groups. Some of these rootstocks are under process of selection and others are commercial rootstocks already introduced into the European market. External visual diagnosis of the scion-rootstock graft combinations was performed by observing symptoms of the ‘translocated’ incompatibility in the nursery. Visual symptoms of ‘translocated’ incompatibility were only found on the Japanese plum cv. ‘Golden Japan’ budded on the plum-apricot hybrid AP-45. The ‘localized’ graft incompatibility was assessed after internal macroscopically examination of graft unions. In the case of the European plum cvs., ‘President’ and ‘Reine Claude Tardive of Chambourcy’ exhibited good graft compatibility with all the tested rootstocks, with the exception of ‘President’ budded on the pentaploid plum hybrid rootstock Damas GF 1869. ‘Reine Claude Verte’ cv. showed ‘localized’ incompatibility with Myrobalan B and Myrobalan GF 3-1 since the second year after budding. ‘Stanley’ cv. showed ‘localized’ incompatibility with the six evaluated peach × almond hybrid rootstocks, although it was compatible with all plum based rootstocks. In the case of Japanese plums, four cultivars (‘Angeleno’, ‘Black Amber’,’ Delbarazur’ and ‘Songold’) did not show any graft incompatibility, but ‘Friar’ showed ‘localized’ incompatibility on Myrobalan B. In the case of peach-almond and P. cerasifera based rootstocks (Adarcias, GF 677, Damas GF 1869, Myrobalan B, Myrobalan 29 C, Myrobalan GF 3-1 and Marianna GF 8-1), ‘Golden Japan’ trees showed similar symptoms to those caused by TomRV in Myrobalan and peach rootstocks and ‘localized’ incompatibility. Finally, this study confirmed the interest of P. insititia specie as well as several interspecific Prunus hybrids as a good source of rootstocks for the plum industry.

Peel water vapour permeance of Japanese plums as indicator of susceptibility to postharvest shriveling

Abstract 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.

Chilling and heat requirements of Japanese plum cultivars for flowering

Abstract 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.

Leaf nutrient content on seven plum cultivars with grafted by budding or own-rooted trees

Abstract Several studies have been conducted in Brazil with rooting of plum scion cultivars, however, it is not known the performance and benefits of own-rooted trees at field. This study aimed to evaluate the leaf nutrient content (N, P, K, Ca, Mg, Fe, Mn, Zn, Cu and B) in seven Japanese plum cultivars (Prunus salicina) on the 2nd and 3rd year after field planting, whose nursery trees were produced by “T-inverted” budding method over ‘Capdeboscq’ peach (P. persica) or by own-rooted hardwood cuttings. The experimental design was in randomized blocks, factorial 7 x 2 (cultivars x nursery tree types), with five replicates of one tree per plot. We conclude that leaf nutrient content of Japanese plums varies among cultivars; however there is no cultivar that stands out in all macro and micronutrients evaluated. K, Ca and Mn leaf contents, when affected by nursery tree types tested, were always higher in own-rooted trees. However, Mg leaf contents, when affected by nursery tree types tested, were always higher in budded trees on ‘Capdeboscq’ peach. Own-rooted plum trees of ‘Amarelinha’, ‘Blood Plum’, ‘Pluma-7’ and ‘Reubennel’ presented higher Mn leaf contents, in relation to budded trees of these cultivars on ‘Capdeboscq’. Own-rooted ‘Cerejinha’ plum trees have highest K leaf content and also increase the agronomic interpretation class in relation to the budded trees of this cultivar on ‘Capdeboscq’.

The effects of anthocyanins on body weight and expression of adipocyte’s hormones: Leptin and adiponectin

The purpose of the study was to assess the effects of anthocyanin-rich Queen Garnet plum juice (QGPJ) on body weight and expression of leptin and adiponectin. Queen Garnet plum is a Japanese plum (Prunus salicina) cultivar developed through a Queensland Government breeding program with very high levels of anthocyanins (272 mg/100 g). Twenty healthy volunteers were supplemented with 200 ml/day of QGPJ and placebo drink for 4 weeks. Supplementation with QGPJ significantly reduces body weight and BMI (p < 0.05) with the average decrease of 0.6 kg in body weight and 0.2 units in BMI over the period of 4 weeks. Furthermore, consumption of QGPJ significantly increases adiponectin blood levels (p < 0.05) (average increase of 3.83 µg/mL) and decreases leptin blood levels (average decrease of 1.31 ng/mL). QGPJ may have potential to be used as a functional food for preventing obesity and obesity related disorders.

Genomic Sequencing of Japanese Plum (Prunus salicina Lindl.) Mutants Provides a New Model for Rosaceae Fruit Ripening Studies.

It has recently been described that the Japanese plum “Santa Rosa” bud sport series contains variations in ripening pattern: climacteric, suppressed-climacteric and non-climacteric types. This provides an interesting model to study the role of ethylene and other key mechanisms governing fruit ripening, softening and senescence. The aim of the current study was to investigate such differences at the genomic level, using this series of plum bud sports, with special reference to genes involved in ethylene biosynthesis, signal transduction, and sugar metabolism. Genomic DNA, isolated from leaf samples of six Japanese plum cultivars (“Santa Rosa”, “July Santa Rosa”, “Late Santa Rosa”, “Sweet Miriam”, “Roysum”, and “Casselman”), was used to construct paired-end standard Illumina libraries. Sequences were aligned to the Prunus persica genome, and genomic variations (SNPs, INDELS, and CNV's) were investigated. Results determined 12 potential candidate genes with significant copy number variation (CNV), being associated with ethylene perception and signal transduction components. Additionally, the Maximum Likelihood (ML) phylogenetic tree showed two sorbitol dehydrogenase genes grouping into a distinct clade, indicating that this natural group is well-defined and presents high sequence identity among its members. In contrast, the ethylene group, which includes ACO1, ACS1, ACS4, ACS5, CTR1, ERF1, ERF3, and ethylene-receptor genes, was widely distributed and clustered into 10 different groups. Thus, ACS, ERF, and sorbitol dehydrogenase proteins potentially share a common ancestor for different plant genomes, while the expansion rate may be related to ancestral expansion rather than species-specific events. Based on the distribution of the clades, we suggest that gene function diversification for the ripening pathway occurred prior to family extension. We herein report all the frameshift mutations in genes involved in sugar transport and ethylene biosynthesis detected as well as the gene CNV implicated in ripening differences.

Carbohydrate and nitrogen reserves in two cultivars of Japanese plum grown under organic and conventional management

Nitrogen and carbohydrate (soluble sugars and starch) reserves were analysed in twig samples of ‘Red Beaut’ and ‘Showtime’ Japanese plum (Prunus salicina Lindl.) cultivars cultivated in two similar experimental orchards under organic and conventional management. ‘Red Beaut’ is a vigorous cultivar while ‘Showtime’ is a middle to low vigorous cultivar. Both cultivars exhibited delayed flowering and premature defoliation under organic management. In general, there were no differences in the concentration of reserves between the two types of management for either of the two plum cultivars, and, likewise, no differences were observed between cultivars, regardless of their vigor. Additionally, reserves were also analysed in plantlets of ‘Mariana 2624’ rootstock (Prunus cerasifera Ehrh × Prunus munsoniana W. Wight &amp;amp; Hedrick) grown in a growth chamber that simulated conditions of spring and autumn periods and subjected to organic or mineral fertilisation. Plants subjected to organic fertilisation were smaller and defoliated earlier, but the sizes of carbohydrate and nitrogen reserves were similar to that of plants grown with mineral fertilisation.