Clonal Rootstocks Research Articles

Structural Disparity of Avocado Rootstocks In Vitro for Rooting and Acclimation Success

Improving clonal rootstock propagation of avocado has been a major industry/research challenge globally for many decades. Tissue culture has been a focus for clonal propagation with substantial advancements in recent years. In the process of tissue culture, avocado rootstocks display differences in rooting and acclimation capacity. Such differences may relate to the specific structural characteristics of the rootstock. This study aimed to investigate the structural difference during tissue culture in two rootstocks ‘Reed’ and ‘Velvick’, with differing rooting and acclimation capacity. Histological investigations were carried out of stem vasculature, leaves and roots of tissue cultured plantlets. Quantitative parameters; stomatal index, stomatal density, trichome density, vein-islet density and vein termination density were also analysed. Prominent fascicular cambium and fewer phloem fibres in stems positively correlated with rooting capacity. Acclimation success positively correlated to the presence of fully differentiated secondary xylem in root. Presence of smaller epidermal cells, high stomatal density and reduced vein termination density was associated with reduced acclimation success. These findings will support optimisation strategies for micropropagation of not only difficult-to-root and difficult-to-acclimate avocado rootstocks, but also, other woody perennials experiencing similar problems.

Early detection of graft-incompatibility in hawthorn (Crataegus azarolus L.) trees on apple, pear, and quince rootstocks

Aim of study: This study was conducted to determine the usability of some clonal rootstocks of apple (MM 106 and MM 111), pear (Fox 11), and quince (Quince A) for hawthorn trees propagation. Area of study: Fruit Research Institute, Isparta and Hatay Mustafa Kemal University, Hatay, Türkiye. Material and methods: ‘Sultan’ hawthorn cultivar was budded on the following clonal rootstocks: pear Fox 11, quince A, and apple MM 106 and MM 111. Plants of hawthorn seedlings (Crataegus azarolus L.) budded with ‘Sultan’ cv. were used as control. External visual diagnosis of the scion-rootstock graft combinations was performed by observing visual symptoms in budded trees growing in nursery conditions, as well as anatomic and histological investigations of the incompatibility in the laboratory. Main results: In this study, healthy scion development and callus tissue in the graft region were formed in the seedling rootstock as well as on Fox11 and Quince A clonal rootstocks. In contrast, MM 106 and MM 111 apple rootstocks showed incompatibility symptoms, with insufficient scion vigor and unstructured callus tissue development. Research highlights: ‘Tanslocated’ and ‘located’ graft incompatibility symptoms were observed in Sultan/MM 106 and Sultan/MM 111 combinations. Further studies are necessary to confirm the early good compatibility found in nursery conditions, testing the effect of those clonal rootstocks from different species (Fox11 and Quince A) on vigor, yield, and fruit quality traits in orchard conditions.

Evaluation of Different Rootstocks and Cultivars on Pruning Weight in Young Pear Trees

This study was carried out to evaluation of the effects on pruning weight (kg plant-1), cumulative pruning weight per plant (kg plant-1), and cumulative pruning weight per hectare (kg ha-1) of 3 quince rootstocks [Quince BA29 (BA29), Quince A (QA), Quince C (MC)] and 3 pear clonal rootstocks (Fox11, OHxF333, Farold 40) and pear seedling rootstocks grafted with 4 standard pear cultivars (‘Abate Fetel’, ‘Deveci’, ‘Santa Maria’, ‘Williams’) between 2019-2021 years. Rootstocks, cultivars, research years and their interactions significantly affected all examined parameters in the study, except for the interaction of year x rootstock x cultivar. Regarding rootstock averages, the highest pruning weight (kg plant-1) was observed from Fox 11, the lowest was in the BA29, QA, and MC quince rootstocks. Regardless of the cultivar averages, the highest pruning weight was in the ‘Deveci’, the lowest was in the ‘Santa Maria’ pear cultivar. The highest pruning weight (kg plant-1) was observed from ‘Deveci’/Fox11, and the lowest was in the ‘Williams’/QA, ‘Williams’/BA29, ‘Abate Fetel’/MC, and ‘Santa Maria’/MC combinations in terms of rootstock x cultivar interaction. The highest cumulative pruning weight per plant (kg) was determined in the ‘Deveci’/Fox11, the lowest was in the ‘Williams’/QA combination in terms of rootstock x cultivar interaction. Furthermore, the highest cumulative pruning weight per hectare (kg) was determined in the ‘Deveci’/Fox11, the lowest was in the ‘Williams’/QA, ‘Williams’/BA29, ‘Abate Fetel’/MC, ‘Santa Maria’/MC, and ‘Santa Maria’/Seedling combination in terms of rootstock x cultivar interaction. Except for the pear seedling rootstock, quince clone rootstocks generally had lower all pruning weight traits than pear clone rootstocks in the study. It can be said that the weaker development of quince rootstocks compared to pear rootstocks causes this situation. According to the results of this study carried out on young pear trees, it can be said that quince rootstocks are somewhat advantageous due to less pruning labor and cost.

Performance of Various Apple Clonal Rootstocks under Temperate Environment using Different Rooting Media and Propagation Techniques

Performance of Various Apple Clonal Rootstocks under Temperate Environment using Different Rooting Media and Propagation Techniques

The influence of four rootstocks on the growth, yield and fruit quality of two plum cultivars

The influence of three clonal rootstocks (‘Pixyʼ, ‘Fereleyʼ and ‘St. Julien Aʼ) along with seedlings of Myrobalan(control) on growth, yield and fruit quality of plum cultivars ‘Čačanska Najboljaʼ and ‘Čačanska Lepoticaʼ was studied in the Belgrade region (Serbia) for the six year-period (2013–2018). In comparison to control, clonal rootstocks have shown a significant effect on the decrease of trunk cross-sectional area. The lowest vigor was found in trees on the ‘Pixyʼ rootstock, then on ‘Fereleyʼ and ‘St. Julien Aʼ. Yield per hectare on trees grafted on clonal rootstocks was higher for 62–82% in ‘Čačanska Najboljaʼ, and for 26–27% in ‘Čačanska Lepoticaʼ compared to Myrobalan. In cultivar ‘Čačanska Najboljaʼ significantly higher fruit weight compared to control was obtained in the trees on the ‘Fereleyʼ and ‘St. Julien Aʼ rootstocks. The effects of rootstocks on the contents of soluble solids and total acids in the fruit were not significant. All three studied clonal rootstocks showed better results than standard Myrobalan, and can be recommended for establishing intensive plum plantations with higher planting density.

METHODS FOR DETERMINING THE COMPATIBILITY OF SCION-ROOTSTOCS COMBINATIONS OF APRICOT AND PEACH

The article presents the results of studies to determine the compatibility of scion-rootstock combinations of apricot and
 peach at the stage of growing planting material in the nursery fields by using different methods. When growing planting material of apricot and peach in the field, three forms of incompatibility are determined to exist: localized disease, starvation of the root system, weak cohesion between the scion and rootstock.
 Initially during laboratory based testing the content of RNA and DNA was determined (using the “ArtRNA MiniSpin” reagent kit) as well as their ratio for 3 clonal rootstocks and 18 scion-rootstock combinations of apricot and peach, on the basis of which the compatibility coefficients were calculated, which made it possible to distinguish three groups: good compatibility (K = 0.01–0.17); medium compatibility (K = 0.18–0.20) and poor compatibility (K > 0.20), coinciding with groups according to the results of agrobiological evaluation in the field. Apricot varieties Znakhodka and Pamyat Loiko, incompatible with the stock VPK-1, were established.

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.

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.

Effects of seedling and clonal West Indian rootstocks irrigated with recycled water on ‘Hass’ avocado yield, fruit weight and alternate bearing

ABSTRACT In modern avocado orchards, ‘Hass’ scions are grafted on selected rootstocks. Avocado rootstocks can be propagated via seeds (seedling rootstocks) or by vegetative propagation (clonal rootstocks). As choice of the proper rootstock influences productivity during the orchard's entire life span, it is critical to evaluate the effects of rootstocks on production parameters of the ‘Hass’ scion. We examined the effects of different rootstocks on fruit yield, fruit weight and alternate bearing of ‘Hass’ scions grafted on nine different West Indian rootstocks. The experiments were conducted from 2009–2019 in two commercial plots located in northwestern Israel irrigated with recycled water. Multiyear mean yield and alternate bearing index (ABI) in Afek orchard ranged from 11,032–15,214 kg ha−1 and 0.26–0.5, respectively. Multiyear mean yield and ABI in Gesher Haziv orchard ranged from 12,746–15,047 kg ha−1 and 0.34–0.57, respectively. Results revealed no significant differences in the multiyear production parameters of the examined rootstocks. However, a non-significant advantage was shown for the vegetative rootstocks, most of which had lower ABI values than the seedling rootstocks. Therefore, because vegetative rootstocks are more expensive to produce, it is practically recommended to use the seedling rootstocks. In the future, it is suggested to examine additional vegetative rootstocks.

Th e eff ect of Osmocote pro mineral fertilizer and plant growth regulators on the biometric parameters of clonal rootstocks 54-118

Obtaining a standard planting material with a closed root system for establishing a basic mother plantations of clone apple clone processes using intensive technology was carried out in protected soil. During the growing season, modern mineral fertilizers and plant growth regulators were used. The aim of the research was to establish the effect of the combined use of plant growth regulators and a complex mineral fertilizer of prolonged action Osmocote Pro on plants of clonal rootstocks 54-118 with a closed root system when cultivated in protected soil. The factors of the experiment were doses of mineral fertilizer (0, 2, 4, 6, 8 gL-1 substrate) and plant growth regulators (IBA, gibberellic acid). It was established that the mineral fertilizer of prolonged action contributes to the realization of the genetic potential of the improved planting material of clonal rootstocks of apple trees to a greater extent than plant growth regulators. Plants with smaller sizes of the aboveground part gave the maximum increase (from 10 to 300 %), with an increase in the initial height of the aboveground part, the increase decreased, which allowed at the end of the season to obtain a leveled source material necessary for establishing basic mother plantations. The maximum increase, 310 % of the initial height of the aboveground part, was observed when Osmocote Pro mineral fertilizer was introduced into plant containers, a dose of 6 gL-1 of substrate and root treatment with plant growth regulator IBA. For plants with an initial height of the aboveground part of 21-40 cm, the greatest increase was obtained with the use of Osmocote Pro mineral fertilizer, a dose of 6 gL-1 of substrate, and treatment with IBA and gibberellic acid. The application of a dose of mineral fertilizer of 8 gL-1 of the substrate caused chlorosis of individual leaves and did not contribute to an increase in the height of the aboveground part of the plants. The maximum height-aligned planting material of clone rootstocks 54-118 was obtained with the combined use of Osmocote Pro mineral fertilizer 4 gL-1 of substrate by treatment plants of gibberellic acid, the coefficient of variation within the variant was 11.4 %.

Infl uence of interference silencing of the gene of translation initiation factors <i>eIF(iso)G</i> and <i>eIF(iso)E</i> on the resistance of the clone stone fruits rootstock 146-2 and commercial plum variety Startovaya to the Plum pox virus

The method of RNA interference gene expression silencing was used to obtain Plum pox virus (PPV) resistant rootstock and commercial variety Startovaya.For this purpose, a vector with self-complementary sequences of the 578 bp eIF(iso)4G and eIF(iso)E genes fragment was created. The eIF(iso)4G and eIF(iso)E genes encodes factors of initiation of translation involved in the life cycle of a Plum pox virus. A strong promoter of the ribulose-1.5-bisphosphate carboxylase/oxygenase (RuBisCo) gene was chosen to drive the expression of RNA interference hairpin in full and truncated variants. Successful genetic transformation of the 146-2 rootstock and variety Startovaya were carried out by A. tumefaciens CBE21 strain. Whole leaves from in vitro cultured shoots were used as an explant source. The nptII and hpt genes coding for neomycin II and hygromycin phosphotransferase were used as a plant-selectable markers. In our experiments, 5 independent transgenic lines of clonal rootstock and variety were obtained and acclimatized to greenhouse conditions. Th eir status was confirmed by PCR and Southern blot analyses. The transformation efficiency was 0.3-0.4 %. One of these lines was grafted with PPV-infected plum buds and its resistance was verified by ELISA. The use of a full-length gene promoter of the small subunit of ribulosobiephosphate carboxylase (RBCS) in the transformation of plants of the Starter variety led to a decrease in plant viability in the case of suppression of the eIF(iso)4E gene and ensured stability at least in the first year after inoculation in the case of suppression of the eIF(iso)4G gene.

Generation of transgenic rootstock plum ((<i>Prunus pumila</i> L.×<i>P. salicina</i> Lindl.)×(<i>P. cerasifera</i> Ehrh.)) using hairpin-RNA construct for resistance to the Plum pox virus

The use of Prunus rootstocks that are resistant to plum pox virus (PPV) is an important agronomic strategy to combat the spread of the Sharka disease in nurseries and orchards. Despite remarkable progress in developing stone fruit rootstocks to adapt to various stresses, breeding that ensures durable virus resistance has not yet been achieved. For this reason, the engineering of PPV resistant plants through genetic transformation is a very promising approach to control sharka disease. The aim of the present study is to produce transgenic plants of the clonal rootstock `Elita`, which is resistant to PPV using ribonucleic acid interference (RNAi) technology. The genetic construct containing the self-complementary fragments of the Plum pox virus coat protein (PPV-CP) gene sequence were used to induce the mechanism of post-transcriptional gene silencing to ensure virus resistance. Transgenic plants have been produced after agrobacterium-mediated transformation of in vitro explanted leaves. The results of polymerase chain reaction (PCR) and Southern blotting analyses confirmed the stable genomic integration of the PPV-CP sense and antisense intronhairpin-RNA sequence. Th e functionality of the introduced expression cassette was confirmed by the activity of including the uidA gene into the transferring T-DNA. To our knowledge, this is the first interspecific plum rootstock produced by genetic engineering to achieve PPV resistance.

Influence of clonal rootstocks on the production process of plum variety Stanley in arid conditions of the Astrakhan region

Relevance. The article presents the results of a three-year study of the economic and biological characteristics of the Stanley plum variety (growth and development of plants, the time of fruiting, productivity, yield, marketable qualities of fruits) when grown on medium-sized clonal rootstocks Evrika-99 and Druzhba, bred at the Crimean experimental breeding station named after N.I. Vavilov, in the acutely arid conditions of the Astrakhan region.Methods.The purpose of the research was to study the influence of medium-sized clonal rootstocks on the production process of the Stanley plum variety in the natural and climatic conditions of the Astrakhan region and to substantiate the possibility of their use for laying intensive plum plantations in the arid conditions of the Northern Caspian Sea.Results. In the course of the research, the influence of the rootstock genotype on the main indicators of productivity was revealed: precocity, yield, commercial qualities of fruits. The early fruiting of the variety was most influenced by the medium-sized rootstock Evrika-99, on which already in the first year of growth in the garden 60-80% of plum trees were noted to bloom. Among the studied rootstocks, the highest rates of yield increase in the Stanley variety were noted on the medium-sized rootstock Evrika-99, in combination with which the variety was characterized by the maximum values of the average yield of 7.6 t/ha, with the values of this indicator on the rootstock Druzhba — 6.7 t/ha , which is 11.8% higher. According to the marketability of the fruit, the rootstock Druzhba was noted, the average weight of which was 48.2 g, which is 18.1% more than on the stock Eureka-99 (40.8 g). In the extremely dry conditions of the Astrakhan region, the Stanley variety is recommended to be grown in an intensive garden on the rootstocks Evrika-99 and Druzhba, which ensure regular and stable yields.

Genetic transformation of clone rootstock of stone fruits 146-2 using the green fluorescent protein reporter gene

For the form of dwarf winter-hardy clonal rootstocks of stone crops146-2 (Prunus pumilaL.xP.tomentosaThunb.), system of regeneration and genetic transformation using green fluorescent protein (GFP) has been developed. For eff ective regeneration of accessory shoots, no pre-treatment with 6-benzylamine-purine (BA) and auxin was required. Stimulation of the regeneration of shoots from leaf explants required 2-3 weeks of a dark period. Th e best percentage of regeneration (greater than 75 %) was observed with a combination of 3 mg/L BA and 0.75 mg/L IBA. The achieved regeneration effi ciency made it possible to develop a protocol for genetic transformation, mediated byAgrobacterium, for rootstock 146-2. Whole leaves from in vitro-cultured shoots were used as explants for transformation by theA. tumefaciensstrain CBE21, with the binary vector pBINmGFP5ER containing thenptIIencoding neomycin phosphotransferase II as a plant-selectable marker under the control of the NOS promoter (nopalin synthase) and the reportergfpgene encoding a green fluorescent protein under the control of the cauliflower mosaic virus (CaMV) promoter 35S. Th e integration ofnptIIandgfpinto transgenes was confirmed by PCR. Expression of the green fluorescent protein was observed using fluorescence microscopy. The efficiency of transformation based on PCR analysis of independent lines resistant to kanamycin was 0.41-0.83 %. All transgenic lines showed resistance to kanamycin at a concentration of 40 mg/L. They were rooted and acclimatized to greenhouse conditions. Th e developed protocols will be used to producePlum pox virus(PPV) resistant plants.

Effect of Weed Management Approaches on Weed Density and Weed Control Efficiency in Apple Nursery Plants Grafted on Clonal Rootstock

Aims: The study aimed to evaluate the influence of different weed management approaches on weed density and weed control efficiency in apple nurseries.
 Study Design: The experimental method used in this study was a Randomized Complete Block Design with seven treatments, each replicated three times.
 Place and Duration of Study: The experiment was set up at the Experimental Farm, Division of Fruit Science, Faculty of Horticulture, Sher-e-Kashmir University of Agricultural Sciences and Technology of Kashmir, Shalimar Campus, Srinagar, Jammu and Kashmir, India during the year 2020.
 Methodology: Seven weed management treatments i.e. manual weeding, pendimethalin @ 1 kg a.i. ha-1, pendimethalin @ 1 kg a.i. ha-1 + manual weeding, paddy straw mulch – 6 cm thick, black polyethylene mulch - 200 micron, weed-free and weedy check were tested in apple nursery (Apple cv. Silver) Spur grafted on M-9 T337 was used as plant material for the study. Weed flora, density, dry weight, and weed control efficiency were all observed and recorded.
 Results: Among different weed management approaches tested, black polyethylene mulch (200 micron) resulted in the lowest weed density and weed dry weight, and the highest weed control efficiency followed by paddy straw mulch (6 cm thick) and pendimethalin @ 1 kg a.i. ha-1 + manual weeding.
 Conclusion: In apple nurseries on clonal rootstock M9-T337, black polyethylene (200 micron) was determined to be the most effective weed control strategy for reducing weed density while increasing overall control efficiency.

Horticultural performance of ‘Hass’ avocado grafted onto seedling and clonal rootstocks under tropical wet-dry climate conditions

In Brazil, avocado nursery trees are traditionally grafted onto seedling rootstocks obtained from chance seedling trees of unknown origin, which results in great tree variability within the commercial orchards. This study aimed at comparing the horticultural performance of ‘Hass' avocado trees grafted onto seedling rootstocks and onto ‘Dusa’ clonal rootstocks, a well-known root-rot tolerant cultivar. Both rootstocks were studied in an ‘Hass’ avocado orchard between year 4 to 8 after planting, by assessing individual fruit yield (number of fruit and kg plant−1), tree size, yield efficiency, Phytophthora cinnamomi presence in the soil under the canopy and fruit quality variables, such as weight, length (L), diameter (D) and L:D ratio. Postharvest fruit quality was evaluated under cold storage at 5°C and ± 85% relative humidity (RH) during a 28-day period. Along a 5-year period,‘Hass’ avocado trees grafted onto ‘Dusa’ clonal rootstock yielded a larger number of bigger and more elongated fruits per tree, which were classified within the most valued fruit size classes in the market, as compared to ‘Hass’ trees grafted onto seedling rootstocks. No significant differences were found between rootstocks regarding postharvest fruit quality or the abundance of P. cinnamomi in the soil under tree canopy.

Efficiency of growing planting material of Russian plum in the conditions of the Moscow region

The results of four-year studies on the reproduction of Russian plum on clonal rootstocks are presented. The purpose of the work was to select the optimal clone rootstocks for replication of the most adaptive varieties of Russian plum. In 2017-2020, in the conditions of the Leninsky district of the Moscow region in the nursery of the Federal Horticultural Research Center for Breeding, Agrotechnology and Nursery, the objects of research were 2 varieties of Russian plum (Shatyor, Cleopatra), grafted on 5 clone rootstocks (SVG-11-19, OD-2-3, 13-113, VVA-1 and Vesennee Plamya). It has been established that the most promising for propagation of Russian plum varieties Cleopatra and Shatyor are clonal rootstocks OD-2-3, 113-113, Vesennee Plamya. The annuals grafted on these rootstocks were characterized by the best biometric parameters of the aboveground system and the number of lateral branches of more than 13 pcs. On the SVG-11-19 and VVA-1 rootstocks, the seedlings were more compact and with fewer lateral branches (6-9 pcs.). The survival rate of the eyes and the yield of annuals of the studied varieties on medium-sized clonal rootstocks Vesennee Plamya and OD2-3 were above 80 %. The maximum yield of standard planting material (40 thousand pieces/ha) was noted in Cleopatra scion/rootstock combinations/ Vesennee Plamya, Shatyor/ OD-2-3 and Shatyor/ Vesennee Plamya. The profitability of growing seedlings of these scion/rootstock combinations was 103.3-109.5 %, which is 1.7 times higher than when grafting these varieties on the VVA-1 rootstock.

The effect of a pulsed magnetic field on the processes of adaptation and vegetative development of microplants of apple clonal rootstocks (<i>Malus</i> Mill.)

Adaptation of microplants to non-sterile conditions is the final stage of clonal micropropagation, which determines the yield of plants and the effectiveness of the entire method as a whole. To increase the survival of microplants, various methods are used, including the use of physical factors, which include exposure to a pulsed magnetic field. The objects of research were microplants of apple clonal rootstocks 54-118 and 57-490. Magnetic pulse processing (MPT) was carried out using the AMIS-8 magnetic pulse stimulation apparatus developed at the Horticulture Federal Research Center. At the stage of adaptation of microplants, MPT had a positive effect on the survival rate and biometric parameters of adapted plants of apple clonal rootstocks 54-118 and 57-490. Under the influence of MPT, the survival rate of microplants of the rootstock of the apple tree 54-118 increased by 50 %, 57-490 — by 25 % compared with the variant without treatment. The trunk diameter on average for 2 forms of apple clonal rootstocks after MPT was 13.3-21.5 % higher than the diameter of the trunk in plants without treatment. Plants of apple clonal rootstocks after MPT formed a more developed leaf apparatus with the number of leaves 1.4-1.6 times more than in control plants.

Survival Rate of Young Pear Trees in Different Rootstock and Cultivar Combinations under Field Conditions: Preliminary Results

This study was carried out to determine the effects of 7 different rootstocks on rootstock diameter (mm), stem diameter (mm), and plant survival ratio (%) of some pear cultivars between 2019-2021. Rootstocks, cultivars, research years, and their interactions significantly affected all examined parameters in the study, except for the interaction of year x rootstock x cultivar. The ‘Deveci’/BA29 and ‘Deveci’/OHxF333 had the largest rootstock and trunk diameters, while the 'Williams'/MC had the smallest. The Fox11 and OHxF333 rootstocks had the highest plant survival ratios, whereas the MC rootstocks had the lowest. In terms of cultivar, the maximum plant survival ratio was found in the ‘Deveci’. At the end of the first 3 years after planting, there was a decrease in the survival ratio of the plants. ‘Williams’ had the lowest rootstock diameter, trunk diameter and survival ratio. The highest trunk diameter was in the OHxF333, BA29, Fox11 and Farold40 rootstocks, and the cultivar was in the ‘Deveci’. Plant survival ratios in quince clonal rootstocks were slightly lower than in pear rootstocks. This is due to the graft incompatibility between quince rootstocks and some pear cultivars. Compatible inter-stock with rootstock and cultivar should be employed to overcome this incompatibility problem caused by localized graft incompatibility. According to the findings of this study on young plants, it is required to extend the research and conduct additional observations in order to give more precise recommendations.

The growing peculiarities of pear tree planting material in conditions of Her-Her community of Vayots Dzor region

The current work pursues production goals, particularly from the prospect of expansion of pear tree nurseries. In our republic the great part of pear tree nurseries dries out due to the bacterial leaf blight, improper selection of rootstock and scion (grafter) varieties, as well as to the random selection of rootstocks. Analyses on the planting stock quality have been conducted during the work implementation in the nursery farm of Herher community considering the inosculation results of various rootstocks. Application of different rootstocks in the nursery farms promotes the establishment of saplings with high survival rate and productivity. It is impossible to develop the branch of horticulture in the Republic of Armenia without the operation of nuresery farm system and sustainable production of healthy, purebred, reliable and high quality planting material. It is relevant to use the seed plants of Willow-leaf pear tree and quince tree rootstock for the pear tree varieties investigated by our research group. Propagation via shrubs has been singled out as an efficient method for clonal rootstock propagation.