Dwarfing Rootstocks Research Articles

Comparative physiological, metabolomic, and transcriptomic analyses reveal mechanisms of apple dwarfing rootstock root morphogenesis under nitrogen and/or phosphorus deficient conditions.

Nitrogen (N) and phosphorus (P) are essential phytomacronutrients, and deficiencies in these two elements limit growth and yield in apple (Malus domestica Borkh.). The rootstock plays a key role in the nutrient uptake and environmental adaptation of apple. The objective of this study was to investigate the effects of N and/or P deficiency on hydroponically-grown dwarfing rootstock 'M9-T337' seedlings, particularly the roots, by performing an integrated physiological, transcriptomics-, and metabolomics-based analyses. Compared to N and P sufficiency, N and/or P deficiency inhibited aboveground growth, increased the partitioning of total N and total P in roots, enhanced the total number of tips, length, volume, and surface area of roots, and improved the root-to-shoot ratio. P and/or N deficiency inhibited influx into roots, and H+ pumps played a important role in the response to P and/or N deficiency. Conjoint analysis of differentially expressed genes and differentially accumulated metabolites in roots revealed that N and/or P deficiency altered the biosynthesis of cell wall components such as cellulose, hemicellulose, lignin, and pectin. The expression of MdEXPA4 and MdEXLB1, two cell wall expansin genes, were shown to be induced by N and/or P deficiency. Overexpression of MdEXPA4 enhanced root development and improved tolerance to N and/or P deficiency in transgenic Arabidopsis thaliana plants. In addition, overexpression of MdEXLB1 in transgenic Solanum lycopersicum seedlings increased the root surface area and promoted acquisition of N and P, thereby facilitating plant growth and adaptation to N and/or P deficiency. Collectively, these results provided a reference for improving root architecture in dwarfing rootstock and furthering our understanding of integration between N and P signaling pathways.

4-methylumbelliferone (4-MU) enhances drought tolerance of apple by regulating rhizosphere microbial diversity and root architecture.

The dwarfing rootstocks-mediated high-density apple orchard is becoming the main practice management. Currently, dwarfing rootstocks are widely used worldwide, but their shallow root system and drought sensitivity necessitate high irrigation requirements. Here, the root transcriptome and metabolome of dwarfing (M9-T337, a drought-sensitive rootstock) and vigorous rootstocks (Malus sieversii, a drought-tolerant species, is commonly used as a rootstock) showed that a coumarin derivative, 4-Methylumbelliferon (4-MU), was found to accumulate significantly in the roots of vigorous rootstock under drought condition. When exogenous 4-MU was applied to the roots of dwarfing rootstock under drought treatment, the plants displayed increased root biomass, higher root-to-shoot ratio, greater photosynthesis, and elevated water use efficiency. In addition, diversity and structure analysis of the rhizosphere soil microbial community demonstrated that 4-MU treatment increased the relative abundance of putatively beneficial bacteria and fungi. Of these, Pseudomonas, Bacillus, Streptomyces, and Chryseolinea bacterial strains and Acremonium, Trichoderma, and Phoma fungal strains known for root growth, or systemic resistance against drought stress, were significantly accumulated in the roots of dwarfing rootstock after 4-MU treatment under drought stress condition. Taken together, we identified a promising compound-4-MU, as a useful tool, to strengthen the drought tolerance of apple dwarfing rootstock.

EVALUATION OF APPLE PLANT VARIETY COMBINATIONS IN THE CONDITIONS OF THE FOREST STEPPE OF THE RIGHT BANK OF UKRAINE

A study on the impact of varietal rootstock combinations on the productivity of apple trees was established at the research station of horticulture of the Institute of National Academy of Sciences of Ukraine in 2013-2014 with 17 new and promising clonal rootstocks for apple trees. At the same time, Amulet, Askolda, Renet Simyrenko, Revena, Ligol, Todes, Jonagored varieties were used as grafts. The growing season of fruit trees began and ended depending on weather conditions. The beginning of vegetation of apple varieties on rootstocks was observed in the first decade of April, and in 2017 and 2020 in the third decade of March. During 2016-2020, the difference between varieties in the rate of bud break was 1-4 days. Flowering of the trees began at the end of April at the beginning of May and lasted for 9-11 days, depending on weather conditions. Over the years of research, an earlier flowering period was characteristic of Askold and Ligol varieties, and in most varieties the flowering phase began on May 2-4. The characteristics of the growth processes of fruit trees of apple trees indicate a direct dependence of the strength of the growth of the tree and the rootstock. In the Revena variety, planted in 2013, the largest increase in the cross-sectional area of the stem was determined in combination with control rootstocks M 9 - 2.71 cm2, 54-118 - 8.32 cm2 and MM106 - 8.40 cm2. In the Askold variety, in the group of dwarf rootstocks, trees in combination with the control rootstock M 9 - 3.10 cm2, with the semi-dwarf rootstock K104 - 9.31 cm2, and on medium growth from the rootstock D 471 - 7.43 cm2 were stronger.According to the Jonagored variety, planted in 2014, a higher researched indicator was established in combination with the dwarf rootstock KD 4 - 3.56 cm2, on the semi-dwarf rootstock 54-118 - 5.58 cm2, medium-growing rootstock D1904 - 7.10 cm2. According to the indicators of the total growth of shoots and the average length of shoots, stronger growth was noted in the group of dwarf rootstocks in the varieties: Revena, Askolda, Renet Simyrenko, Amulet in combination with rootstock M9. Also, with the use of semi-dwarf rootstocks, a stronger growth of one -year shoots was noted in the varieties: Revena in combination with the control rootstock 54-118 – 53.2 cm, Amulet, Renet Simyrenko, and Askolda with rootstock K 104, respectively 60.9 cm, 67.5 cm, and 73.2 cm, on a medium-sized rootstock, the strongest growth was noted in all varieties of apple trees in combinations with D 1904 rootstock. The volume of the crown of the tree depended on the pomological variety and rootstock. From the use of dwarf rootstocks, a larger crown volume was noted in the varieties Amulet (5.0 cm3), Renet Simyrenko (8.4 cm3) with the control rootstock M 9, in the variety Revena (1.92 cm3) with the rootstock KD 4, in the variety Askolda (3.3 cm3) with rootstock D 3038 and on a semi-dwarf rootstock - in varieties Askolda (12.7 cm3), Renet Simyrenko (14.28 cm3) with rootstock K 104. In terms of yield, the highest indicator was the Revena variety on rootstocks M 9 - 15.7 t/ha, 54-118 - 11.5 t/ha and MM 106 - 9.8 t/ha. At the same time, a higher fruit yield of the Askold variety was obtained in combination with dwarf rootstocks D 1071 - 13.7 t/ha and D 3038 - 13.8 t/ha and in the variant with the M9 rootstock, where the value was 13.0 t/ha and with a medium-sized control rootstock MM 106. Thus, for the Renet Simyrenko apple variety, the highest yield was recorded in combination with the D 1071 dwarf rootstock - 11.1 t/ha, which was 21% higher than the M 9 rootstock, and in combination with the semi-dwarf Baturyn rootstock, the yield decreased and amounted to only 3, 5 t/ha, Slobozhanska - 3.3 t/ha and D 1161 - 6.8 t/ha. One of the indicators of marketability of the crop is the average fruit weight. The average weight of the fruits in the variety rootstock combinations was the largest in the trees of the control variety rootstock combination, namely: M 9, 54-118, MM 106, and already in the varieties planted in 2014, the highest average fruit weight was obtained with dwarf rootstocks D 1071, D 3038 . However, in combinations with Revena, Amulet, and Todes varieties with rootstocks Sambirska, D 1071, fruits of the highest and first varieties prevailed - 92.2-93.0%

Exogenous 24-epibrassinolide promoted growth and nitrogen absorption and assimilation efficiency of apple seedlings under salt stress.

High salinity significantly hampers global agricultural productivity. Plants typically undergo lower nitrogen utilization efficiency (NUE) under salt stress. As an active byproduct from brassinolide biosynthesis, 24-epibrassinolide (EBR) is involved in regulating the stress-treated plant N absorption and assimilation. However, the exogenous EBR application effects' on N absorption and assimilation in apple exposed to the salt-stressed condition remains unclear. We sprayed exogenous EBR (0.2 mg L-1) on apple dwarf rootstock (M9T337) seedlings (growing hydroponically) under salt (NaCl) stress in a growth chamber. We analyzed the seedling development, photosynthesis and its-mediated C fixation, N ( ) absorption and assimilation in reponse to exogenous EBR application under salt stress. The findings demonstrated that NaCl stress greatly hampered seedlings' root growth and that exogenous EBR application obviously alleviated this growth suppression. Exogenous EBR-treated plants under NaCl stress displayed the more ideal root morphology and root activity, stronger salt stress tolerance and photosynthetic capacity as well as higher C- and N-assimilation enzyme activities, ion flow rate and nitrate transporter gene expression level than did untreated plants. Furthermore, the results of isotope labeling noted that exogenous EBR application also enhanced 13C-photoassimilate transport from leaves to roots and 15 transport from roots to leaves under NaCl stress. Our findings imply that exogenous EBR application, through strengthening photosynthesis, C- and N-assimilation enzyme activities, nitrate absorption and transport as well as synchronized optimizing the distribution of seedlings' C and N, has a fundamental role in improving NUE in apple rootstock seedlings under salt stress.

Dwarfism in Fruit Plants: A Review

In this modern era, farmers are adopting high density planting (HDP) for most of the fruit crops. Dwarfing is based on the principle of making the optimal use of vertical and horizontal space per unit time and harnessing the highest potential returns per unit of inputs and natural resources. Dwarfing in fruit crops can be accomplished through a variety of methods, including the use of dwarfing rootstock, the selection of spur type scion cultivars, use of interstock, pruning, root pruning, various training systems, girdling, scoring, bark invasion and the application of growth retardants. One strategy for promoting early fruiting, less vigour and increasing production is to utilize dwarf root stocks. The mechanism underlying dwarfing involves anatomical, physiological and biochemical changes. It has been proposed that dwarfing rootstock or interstock control tree size by regulating the auxin that passes through the rootstock or interstock’s bark. Paclobutrazol retards growth, shoot elongation and reduced internodal length by inhibiting gibberellins synthesis. Dwarfness can be imparted by the using incompatible rootstock. Dwarfing can be induced by inducing viral infection, although, it is not commercially adopted. Recombinant DNA technology has recently expanded the gene pool that can be managed to cause dwarfism and maximize benefits in horticulture crops.

Effect of Drip Irrigation, N, K, and Zn Coupling on Pn of Densely Cultivated Apple on Dwarf Rootstock in Xinjiang, China

This study aimed to determine the effect of irrigation amount (W), nitrogen (N), potassium (K), and zinc (Zn) on the net photosynthetic rate (Pn) of closely planted apple trees on dwarf rootstocks in arid areas of Xinjiang. Taking the “Royal Gala” apple as the experimental material, a mathematical model for Pn was established using the principle of four-factor five-level quadratic regression with a general rotation combination design. The results show that: (1) The regression equations reached significant levels (F = 37.06 > F0.01(11.11) = 4.54). (2) The effect of W, N, K, Zn on Pn is significant with relative importance W > N > Zn > K. (3) The results of single factor analysis showed that with an increase in W, N, K, and Zn, Pn exhibits an n-shaped parabolic response. (4) The positive coupling between W and N is significant, and the positive coupling between W and Zn is also significant. (5) Analysis of the interaction between sets of three factors revealed that W, N, and Zn could be combined to best effect, with the maximum value reaching 12.77 μmol·m−2·s−1. Compared with W×K×Zn and W×N×K, the combination of W×N×Zn reduces W by 9.2% and 6.3%, respectively, which indicates its suitability for use in the dry and water deficient planting environment in Xinjiang. (6) Within the 95% confidence level, when W is 258–294.75 mm, N is 33.44–39.51 kg/hm2, K is 53.82–69.39 kg/hm2, and Zn is 6.46–7.84 kg/hm2, the net photosynthetic rate reaches 11 μmol·m−2·s−1.

Mutagenic-sensitivity and variability in the putative mutants of polyembryonic mango genotypes

Polyembryonic mango genotypes are considered the best resources for developing rootstocks owing tothe production of uniform, true-to-type nucellar seedlings with the deep tap root systems. However, their use inbreeding programmes is often limited by a narrow genetic base due to maternal inheritance. Hence, enhancementin or creation of variability for traits of interest becomes a pre-requisite, if rootstock breeding in mango has tobe undertaken. In this study, we attempted to induce variability in polyembryonic mango genotypes, Bappakkai,Nekkare and Kurukkan by treating their kernels with different doses of gamma rays ranging from 15 to 35 Gy.The results revealed delayed germination and a decrease in germination percentage with increasing dosageof gamma irradiation. The lethal dose (LD50) values for gamma radiation were determined, based on the seedgermination percentage using Probit analysis values, which were 22.39 Gy, 19.95 Gy, and 19.95 Gy for Bappakai,Nekkare and Kurukkan, respectively. Other traits like the number of seedlings emerging per kernel, plant height,inter-nodal length, and the number of leaves showed a gradual decrease in their mean values with increasingirradiation dosage. The results suggest the effectiveness of induced mutation in bringing about variability intraits like plant height for developing dwarf rootstocks to be used in high-density planting.

Physiological and Full-Length Transcriptome Analyses Reveal the Dwarfing Regulation in Trifoliate Orange (Poncirus trifoliata L.)

Dwarfing rootstocks are capable of high-density planting and are therefore urgently needed in the modern citrus cultivation system. However, little is known about the physiological relevance and molecular basis underlying citrus height. This study aimed to comprehensively analyze phytohormone, carbohydrate, and associated transcriptome changes in the stem of two weak growth rootstocks ('TO' and 'FD') relative to the vigorous 'CC' rootstock. The phenotypic observation revealed that the plant height, plant weight, and internode length were reduced in dwarfing rootstocks. Moreover, the contents of indole-3-acetic acid (IAA), trans-zeatin (tZ), and abscisic acid (ABA), were higher in TO and FD rootstocks, whereas the gibberellin 3 (GA3) content was higher in the CC rootstocks. The carbohydrate contents, including sucrose, fructose, glucose, starch, and lignin significantly decreased in both the TO and FD rootstocks. The full-length transcriptome analysis revealed a potential mechanism regulating dwarfing phenotype that was mainly related to the phytohormone signaling transduction, sugar and starch degradation, lignin synthesis, and cellulose and hemicellulose degradation processes. In addition, many transcription factors (TFs), long non-coding RNAs (lncRNAs), and alternative splicing (AS) events were identified, which might act as important contributors to control the stem elongation and development in the weak growth rootstocks. These findings might deepen the understanding of the complex mechanisms of the stem development responsible for citrus dwarfing and provide a series of candidate genes for the application in breeding new rootstocks with intensive dwarfing.

Analysis of the Small Auxin-Up RNA (SAUR) Genes Regulating Root Growth Angle (RGA) in Apple.

Small auxin upregulated RNAs (SAURs) are primary auxin response genes; the function of regulating root growth angle (RGA) is unclear in the apple rootstock. We firstly identified 96 MdSAUR genes families from new apple genome GDDH13 using the resequence database of 'Baleng Crab (BC)' and 'M9'. A total of 25 MdSAUR genes, regulating the formation of RGA, were screened for the expression profiles in stems and roots and the allelic variants of quantitative trait loci (QTL). Finally, through the joint analysis of network and protein-protein interaction, MdSAUR2, MdSAUR29, MdSAUR60, MdSAUR62, MdSAUR69, MdSAUR71, and MdSAUR84 were screened as the main candidate genes for regulating RGA. This study provides a new insight for further revealing the regulatory mechanism of RGA in apple dwarf rootstocks.

A Mini Review of Citrus Rootstocks and Their Role in High-Density Orchards.

Dwarfing is an important agricultural trait for intensive cultivation and effective orchard management in modern fruit orchards. Commercial citrus production relies on grafting with rootstocks that reduce tree vigor to control plant height. Citrus growers all over the world have been attracted to dwarfing trees because of their potential for higher planting density, increased productivity, easy harvest, pruning, and efficient spraying. Dwarfing rootstocks can be used to achieve high density. As a result, the use and development of dwarfing rootstocks are important. Breeding programs in several countries have led to the production of citrus dwarf rootstocks. For example, the dwarfing rootstocks 'Flying Dragon', 'FA 517', 'HTR-051', 'US-897', and 'Red tangerine' cultivated in various regions allow the design of dense orchards. Additionally, dwarf or short-stature trees were obtained using interstocks, citrus dwarfing viroid (CDVd) and various chemical applications. This review summarizes what is known about dwarf citrus rootstocks and the mechanisms underlying rootstock-scion interactions. Despite advances in recent decades, many questions regarding rootstock-induced scion development remain unanswered. Citrus rootstocks with dwarfing potential have been investigated regarding physiological aspects, hormonal communication, mineral uptake capacity, and horticultural performance. This study lays the foundation for future research into the genetic and molecular mechanisms underlying citrus dwarfing.

Incompatibility Selected Dwarf Rootstock and Scion of Citrus sp. regard to Abiotic Stress Tolerant

This study aims to determine the response’s incompatibility of selected dwarf citrus rootstock after treated by abiotic stresses such as drought, waterlogging, and acidity on a scion. The results of this study was selected seedlings for sub-optimal lands in Indonesia with dwarf growth characteristic and compatible with the grafted-scion. The preliminary study has shown that there were 3 (three) selected rootstock accessions with dwarf characteristics, namely Citromello (Cit), Volkameriana (Volk), and Cleopatra Mandarin (CM). The seeds of these accessions were treated with 8% Polyethylene Glycol (PEG), 150% FC; 9 mM Al2SO4 at eight months after planting. Each rootstock was grafted with Pontianak orange (C. nobilis var. microcarpa). The results showed that Citromello (Cit) and Volkameriana (Volk) are incompatible rootstock and dwarf potential seedling. However, Cleopatra Mandarin has a compatibility with the grafted scion and is tolerant of abiotic stress treatments. The effect of abiotic treatment on Citromello resulted in 15% higher root length higher than other accessions. Furthermore, this variety has 40% dry weight and 25% lateral root numbers, respectively, by Al2SO4 and PEG. Meanwhile, Volkameriana had the 40% higher number of leaves.

Interaction of MdWRKY24 and MdRGL in Response to Tree Dwarfing in Malus domestica

In apple cultivation, dwarf rootstocks are chosen for dense planting and intensive cultivation, which is beneficial to production management. Dwarf rootstocks are widely used in apple production in China. However, the dwarfing mechanisms of dwarf interstock are still unclear. Here, M9 and SH40 were selected as the dwarf interstocks for potted Fuji apples. The key transcription factor MdWRKY24 was screened via transcriptional sequencing. The open reading frame sequence of the MdWRKY24 gene was 657 bp in length, encoded 218 amino acids, and was located on the cell membrane. The MdWRKY24-overexpressing Arabidopsis line showed a dwarf phenotype and delayed flowering. The DELLA protein RGA-like (RGL) gene is a repressor of the gibberellin signaling pathway. Yeast two-hybrid analysis revealed that MdWRKY24 could interact with MdRGL1/2/3. The results indicated that MdWRKY24 might affect plant dwarfing through the synergistic effect of MdRGL1/2/3. The MdWRKY24-MdRGL may be an important pathway underlying the gibberellin-mediated regulation of apple dwarfing.

Evaluation of dwarf rootstocks for high-density and sustainable orchards in Latvia

Evaluation of dwarf rootstocks for high-density and sustainable orchards in Latvia

Phenotypes of Citrus Sp. As a Selected in Dwarf Rootstock Material Regard to Abiotic Stress Tolerance

Research on abiotic stress tolerant horticultural plants has been widely carried out. However, there has not been much research on the citrus phenotype with rootstock as planting material, which has advantages in overcoming abiotic stress and dwarf performance. This research provides citrus rootstock that is tolerant to some of the marginal land in Indonesia especially on drought, salinity, waterlogging, and acidity. This morphological research was conducted at Punten Experimental Garden in Batu city, Indonesia. Anatomical observations were carried out in the laboratories of Indonesian Balitjestro and Universitas Brawijaya. This has done pre-treatment selection lasted for 8 months and then abiotic stress treatment lasted for 2 months, from July to September 2021. This study consisted of 15 treatment combinations: three rootstock varieties, i.e., Citromello (Cit), Volkameriana (Volk), and Cleopatra mandarin (CM), and five abiotic stress treatments, i.e., control, PEG 10%, NaCl 3.5%, waterlogging 150% FC, and 9 mM Al2SO4. The results showed that abiotic stress, especially NaCl and waterlogging, caused phenotypic changes such as in leaf shape, i.e., leaf lamina shape, reduced leaf area, chlorophyll content, stomata density, and canopy diameter compared to other abiotic stresses. The best stomatal density and open stomata percentage were for Cleopatra mandarin (CM). This was also shown by the increase in proline content when plants are subjected to abiotic stresses, especially in Cleopatra mandarin under NaCl stress, Volkameriana under Al2SO4 stress, and Citromello under waterlogging (WL). The palisade size decreased, its vascular bundles in the leaves increased, and the pore distribution changed. The results showed all rootstock candidates were resistant to several abiotic stresses and had dwarf performance. It can be concluded that the best tolerant of abiotic stress rootstock variety of abiotic stress is Cleopatra mandarin, while Volkameriana and Citromello are better tolerant on acidic soil.

An Improved Apple Object Detection Method Based on Lightweight YOLOv4 in Complex Backgrounds

Convolutional neural networks have recently experienced successful development in the field of computer vision. In precision agriculture, apple picking robots use computer vision methods to detect apples in orchards. However, existing object detection algorithms often face problems such as leaf shading, complex illumination environments, and small, dense recognition targets, resulting in low apple detection rates and inaccurate localization. In view of these problems, we designed an apple detection model based on lightweight YOLOv4—called Improved YOLOv4—from the perspective of industrial application. First, to improve the detection accuracy while reducing the amount of computation, the GhostNet feature extraction network with a Coordinate Attention module is implemented in YOLOv4, and depth-wise separable convolution is introduced to reconstruct the neck and YOLO head structures. Then, a Coordinate Attention module is added to the feature pyramid network (FPN) structure in order to enhance the feature extraction ability for medium and small targets. In the last 15% of epochs in training, the mosaic data augmentation strategy is turned off in order to further improve the detection performance. Finally, a long-range target screening strategy is proposed for standardized dense planting apple orchards with dwarf rootstock, removing apples in non-target rows and improving detection performance and recognition speed. On the constructed apple data set, compared with YOLOv4, the mAP of Improved YOLOv4 was increased by 3.45% (to 95.72%). The weight size of Improved YOLOv4 is only 37.9 MB, 15.53% of that of YOLOv4, and the detection speed is improved by 5.7 FPS. Two detection methods of similar size—YOLOX-s and EfficientNetB0-YOLOv3—were compared with Improved YOLOv4. Improved YOLOv4 outperformed these two algorithms by 1.82% and 2.33% mAP, respectively, on the total test set and performed optimally under all illumination conditions. The presented results indicate that Improved YOLOv4 has excellent detection accuracy and good robustness, and the proposed long-range target screening strategy has an important reference value for solving the problem of accurate and rapid identification of various fruits in standard orchards.

SUITABILITY OF COMMERCIAL APPLE VARIETIES ON DWARF ROOTSTOCKS FOR GROWING ACCORDING TO DENSIFIED PATTERNS

In order to assess the suitability of apple varieties that differ in the type of fruiting and genetic potential for productivity
 of apple varieties on dwarf rootstocks for growing according to densified patterns and to identify the optimal placement
 pattern for each scion-rootstock combination in the experimental orchard of RUE “Institute of Fruit Growing”, an orchard
 was planted with annual seedlings of three commercial varieties on dwarf rootstocks: Belorusskoe Sladkoe on M-9 and PB-4,
 Imant on 62-396 and PB-4, Nadzejny on 62-396, M-9 and PB-4 in the spring of 2010. Planting schemes for all scion-rootstock
 combinations are 3.5 × 1.5 m (1904 trees/ha) and 3.5 × 1.0 m (2857 trees/ha). The full realization of the productivity potential of varieties was ensured by denser placement of trees according to the planting pattern of 3.5 × 1.0 m (2857 trees/ha) and dwarf rootstock 62-396 – for Imant and Nadzejny varieties, dwarf rootstock M-9 – for Belorusskoe Sladkoe and Nadzejny varieties. Rootstock PB-4 did not solve the problems of intensive commercial fruit growing.

REALIZATION OF GENETIC POTENTIAL AND DURATION OF THE PRODUCTION PHASE OF APPLE TREE VARIETIES IN INTENSIVE PLANTATIONS

Studies to determine the realization of the genetic potential and the duration of the productive phase of apple Alesya and
 Vesyalina varieties on two clonal rootstocks of different intensity of growth with two tree placement pattern were carried out
 in 2008–2021 in the garden of the Department of Fruit Growing Technology of RUE “Institute of Fruit Growing”, planted in the spring of 2006 with one-year-old seedlings. The productivity potential is more fully revealed in the variety Alesya on a dwarf rootstock 62-396 with a planting pattern of 4.0 × 1.5 m, in the variety Vesyalina on a semi-dwarf rootstock 54–118 with a planting pattern of 4.0 × 2.0 m. Relatively high productivity rate of the Alesya variety was also noted on the semi-dwarf rootstock 54–118 with a planting pattern of 4.0 × 2.0 m. We recommend these designs of apple plantations for laying and growing intensive orchards in the Republic of Belarus. The standard lifespan of apple plantations on a semi-dwarf (medium) rootstock can be reduced to 12 years, as well as for apple plantations on a dwarf rootstock. Fast depreciation with high yields allows for a faster replacement of orchards, and therefore varieties and methods of agricultural practices.

PbXND1 Results in a Xylem-Deficient Dwarf Phenotype through Interaction with PbTCP4 in Pear (Pyrus bretschneideri Rehd.).

Dwarfing is an important agronomic characteristic in fruit breeding. However, due to the lack of dwarf cultivars and dwarf stocks, the dwarfing mechanism is poorly understood in pears. In this research, we discovered that the dwarf hybrid seedlings of pear (Pyrus bretschneideri Rehd.), ‘Red Zaosu,’ exhibited a xylem-deficient dwarf phenotype. The expression level of PbXND1, a suppressor of xylem development, was markedly enhanced in dwarf hybrid seedlings and its overexpression in pear results in a xylem-deficient dwarf phenotype. To further dissect the mechanism of PbXND1, PbTCP4 was isolated as a PbXND1 interaction protein through the pear yeast library. Root transformation experiments showed that PbTCP4 promotes root xylem development. Dual-luciferase assays showed that PbXND1 interactions with PbTCP4 suppressed the function of PbTCP4. PbXND1 expression resulted in a small amount of PbTCP4 sequestration in the cytoplasm and thereby prevented it from activating the gene expression, as assessed by bimolecular fluorescence complementation and co-location analyses. Additionally, PbXND1 affected the DNA-binding ability of PbTCP4, as determined by utilizing an electrophoretic mobility shift assay. These results suggest that PbXND1 regulates the function of PbTCP4 principally by affecting the DNA-binding ability of PbTCP4, whereas the cytoplasmic sequestration of PbTCP4 is only a minor factor. Taken together, this study provides new theoretical support for the extreme dwarfism associated with the absence of xylem caused by PbXND1, and it has significant reference value for the breeding of dwarf varieties and dwarf rootstocks of the pear.

Developing New Cultivars of Prunus × Rossica Erem. And Clonal Rootstocks at the Krymsk Experiment Breeding Station

Abstract The paper considers the possibilities of expanding the assortment of plum cultivars in world production by hybridising large-fruited myrobalan plum (Prunus cerasifera Ehrh.) cultivars with those of Japanese plum (Prunus salicina Lindl.) and other diploid stone fruit species. Because of many years of breeding work in Russia, cultivars of a new hybridogenous species Prunus × rossica Erem. (Russian plum) have been created, which can ensure a stable supply of fresh fruit from late June to September and complement the assortment of common plum cultivars. A description is given for the best adaptive, high-yielding cultivars with good taste and high canning qualities — ‘Kubanskaya Kometa’, ‘Globus’, ‘Gek’, ‘Iyulskaya Roza’, ‘Dynnaya’, ‘Kolonnovidnaya’, and ‘Podarok Sad-Gigantu’. The efficiency of their cultivation using intensive technologies and own-rooted plants, as well as clonal rootstocks bred at the Krymsk Station, has been shown. It is recommended to carry out intensive cultivation of Russian plum using medium vigorous rootstocks like Kuban 86, Evrika 99, Zarevo, Fortuna and dwarf rootstocks VVA 1, Best, Upryamets and VSV 1.

Influence of Citrus Rootstocks on Scion Growth, Hormone Levels, and Metabolites Profile of ‘Shatangju’ Mandarin (Citrus reticulata Blanco)

Dwarfing rootstocks are a valuable genetic resource for managing high-density plantations. The selection of the appropriate scion/rootstock combination is key to improving crop performance and sustainable production in a particular environment and specific training systems. ‘Shatangju’ mandarin scion cultivar grafted onto ‘Flying Dragon’ rootstock tends to be dwarfing and develops short stature plants. To obtain insight into potential mechanisms underlying rootstock-induced dwarfing effects, we conducted a rootstock trial to examine the influence of 11 different rootstocks based on their growth vigor, antioxidants, and hormonal levels of the scion cultivar. The phenotypic observations revealed that size reduction in the ‘Flying Dragon’ rootstock is due to lower node number, shorter internodal length, and a reduced trunk diameter of the scion compared with more vigorous rootstocks. Antioxidant analysis showed that ‘Shatangju’ mandarin grafted onto ’Flying Dragon’ and ‘Trifoliate Orange’ rootstock had significantly lower peroxidase (POD) activity than other tested rootstocks. The hormonal analysis indicated that there were markedly lower amounts of abscisic acid (ABA) in ‘Shatangju’ mandarin grafted with ‘Flying Dragon’ rootstock. In addition, trees grafted with ‘Sour Pummelo’ and ‘Flying Dragon’ depicted minimum amounts of gibberellins (GA24). Moreover, several metabolites associated with organic acids, flavonoids, amino acids, and alkaloids responded differently in plants grafted with ‘Flying Dragon’ (dwarfing) and ‘Shatang Mandarin’ (vigorous) rootstocks. This study concluded that ‘Flying Dragon’ rootstock with a strong dwarfing effect has been proposed to improve high-density cultivation methods. These findings will provide useful insights for future research associated with rootstock-mediated dwarfing mechanisms of citrus rootstocks.