Columnar Apple Trees Research Articles

Construction of new genomes of columnar apple trees in the Russian research institute of fruit crop breeding

Relevance. The article presents data on the creation of new genotypes of columnar apple trees based on interval crossings of the 2x × 4x type using traditional breeding methods and elements of accelerated assessment of hybrid forms using cytoembryological and molecular genetic methods.Results. Cytological assessment of seedlings obtained from the studied interval crossings of six columnar apple varieties and the selected columnar form 29-35-123 with tetraploid forms 30-47-88 and 25-37-45, which are donors of diploid gametes, showed that seedlings with a triple set of chromosomes prevail and their share is 83.0%. The share of diploids accounts for 17.0%. A comparative assessment of the ploidy of offspring showed that the difference between the yield of triploid seedlings in the offspring of families where different donors of diploid gametes (25-37-45 and 30-47-88) were taken as paternal forms is insignificant. From the tetraploid 30-47-88, 81.7% of triploid offspring were obtained, from 25-37-45 — 91.3%.The data of molecular genetic analysis confirm that in combinations where both parents have the scab immunity gene, the yield of immune seedlings is high (70,7%) and corresponds to the splitting on this basis in a ratio of 3:1. n families where only one of the parents carries the Rvi6 gene in its genotype (Garland × 25-37-45, 29-35-123 × 25-37-45, Moscow necklace × 30-47-88 and Constellation × 25-37-45) immune seedlings were less common (52%). A unique combination of columnarity, the Rvi6 gene and a triple set of chromosomes in one genotype is characteristic of 23.1% of seedlings.

Effect of Bacillus subtilis – based microbiological preparations on the numerical composition of cultured forms of endophytic bacteria, content of mineral nutrition elements, photosynthetic pigments, as well as on chlorophyll fluorescence indices in leaves of columnar apple trees

The results of agrochemical field experiments conducted in an orchard of columnar apple tree (Malus domestica Borkh.) in the Moscow Oblast during the period of 2021–2022 are presented. The research objects were the ‘Valuta’, ‘Triumph’, and ‘President’ varieties. The effect of foliar treatments of plants with Bacillus subtilis (strain V167) and Bacillus subtilis (strain V417) strains, as well as Bacillus subtilis – based microbiological preparations “Extrasol” (strain Ch13) and “Phytosporin-M” (strain 26D) on such indicators as the microbiological and chemical composition of leaves, the content of photosynthetic pigments in leaves, and chlorophyll fluorescence indices was studied. Plant samples were analyzed using standard methodology. When applying strains and microbiological preparations based on Bacillus subtilis, the taxonomic composition of endophytic bacterial forms cultured on dense nutrient media and isolated from leaves was represented by the Bacillus genus. For comparison, when treating plants with Bacillus subtilis strain V417 and “Phytosporin-M”, the Pseudomonas genus was also detected. The number of cultivated forms of endophytic bacteria in the treated plants was consistently growing, having reached the maximum value of 406800 CFU/g in the “Extrasol” variant. Notably, the content of photosynthetic pigments in leaves depended on both the plant variety and the strain used. High values of maximal efficiency of PSII photochemistry (Fv/Fm) were observed both in experimental and control variants. A consistent increase in leaf N content was detected when applying “Extrasol”. In this respect, the ‘President’ variety showed the greatest response, i.e., a 16.1 % increase compared to the control. The ‘President’ and ‘Triumph’ varieties demonstrated an increase in leaf K content under the influence of foliar treatment of plants with the studied strains and microbiological preparations. The greatest effect of 17.2 % above the control was observed in the ‘Triumph’ variety when treated with “Extrasol”. Foliar treatments of ‘President’ and ‘Valuta’ plants with microbiological preparations contributed to increased, compared to the control, Mg contents in their leaves.

Different crop load management on columnar apple trees: first year results

Different crop load management on columnar apple trees: first year results

Influence of mineral, organic, organomineral fertilization on winter hardiness components of columnar apple tree (<i>Malus domestica</i> Borkh.)

Intensive biological technologies of apple-tree cultivation with application of organic and mineral fertilizers form high nitrogen nutrition, thus leading to prolonged growth of fruit plants and reducing their winter hardiness. Columnar apple tree fail to demonstrate high potential for winter hardiness. Therefore, research into regularities and mechanisms behind the influence of nutritional status of columnar apple tree on indicators of plant winter hardiness is considered relevant. The research was aimed at establishing the influence of mineral, organic, organomineral fertilization on the components of winter hardiness of columnar apple trees grown on podzolic soil. Materials and methods. The research involved the ‘Triumph’, ‘President’, ‘Ostankino’ columnar apple varieties, as well as organic and mineral fertilizers. The experiment was conducted in 2016–2021 in the agrochemical experiment station of the Federal Horticultural Center for Breeding, Agrotechnology and Nursery (Moscow region) on podzolic soil of medium-loam particle size distribution. The experimental design included 4 variants: 1) control without fertilizers; 2) N90K90; 3) organic fertilizers 100 t/ha; 4) N90K90 organic fertilizers 100 t/ha. Naa (ammonium saltpeter), KCl mineral fertilizers were applied annually, organic fertilizer (horse manure with sawdust) was applied in 2014. Winter hardiness components and plant samples were analyzed according to generally accepted methods. According to the research into the influence of mineral, organic, organomineral fertilization on the components of winter hardiness of columnar apple tree (Malus domestica Borkh.) grown on podzolic soil in the conditions of the Moscow region, the fertilizer is found inefficient in terms of providing the optimal level of nitrogen nutrition of columnar apple tree plants, except for ‘Triumph’ variety when getting organic fertilizers at a dose of 100 t/ha. In January, fructose prevailed in the sugars of annual shoots of columnar apple tree plants. The ‘Triumph’ and ‘President’ varieties showed a tendency to increase in the content of fructose and glucose as compared with the control when getting organic fertilizers and their combination with mineral fertilizers. The same tendency was observed in the ‘Ostankino’ variety for the content of ascorbic acid in annual shoots, whereas this indicator of the ‘Triumph’ and ‘President’ varieties demonstrated the opposite trend. The ascorbic acid content in annual shoots in winter appeared consistent with its content in August shoots and remained independent on the content in leaves in August. With a decrease in temperature to -40 °C (component II of winter hardiness), the ‘Triumph ‘and ‘Ostankino’ varieties suffered reversible damage to the vegetative buds from 0 to 2.0 points, the ‘President’ variety introduced with 100 tons/ha organic fertilizers demonstrated an increase in damage to the vegetative buds to 3.17 points. The greatest damage to reproductive buds in the ‘President’ and ‘Ostankino’ varieties (3.85-3.91 on the control) was observed in component II of winter hardiness. The application of mineral and organic fertilizers increased these damages to complete death of reproductive buds. Injuries to bark, cambium in all variants of the studied varieties did not exceed 2.0 points. Wood appeared more damaged in the ‘Ostankino’ variety (up to 4.03 points in the combined application of N90K90 and 100 t/ha of organic fertilizers) as well as in the Triumph variety (up to 3.80 points in the N90K90 variant). As for component III of winter hardiness, an irreversible damage was noted for reproductive buds of the studied varieties in all variants of the experiment. In terms of component IV of winter hardiness, irreversible changes occurred in reproductive buds to the greatest extent (complete death in the ‘Triumph’ and ‘President’ varieties); in the tissue under reproductive buds, to the greatest extent in the ‘President’ variety (3.07 points in the variant of 100 tons/ha of organic fertilizers) and in the ‘Ostankino’ variety (2.76 points in N90K90), at the core, the maximum damage was noted in the N90K90 variant in the ‘Triumph’ (3.22 points) and ‘Ostankino’ (2.76 points) varieties.

Method of Precise Irrigation and Fertilization Using a Group of Autonomous Robotic Agents

Today, climate change, the limited availability of natural resources, coupled with an increase in total consumption, constantly increase the requirements for agricultural facilities. One of the urgent tasks in the field of robotic agricultural automation systems is the task of developing methods and approaches to precise irrigation and fertilization, characterized by a high level of autonomy, a wide working area and the ability to perform tasks in a continuous mode. Thus, within this study, a method of precise fertilizer application was proposed, based on the use of a group of heterogeneous robotic means. The heterogeneous composition of the system provides the possibility of replacing batteries and replenishing the solution tanks of the robotic means, which carry out the application of fertilizers in the areas of operations through the use of specialized ground robots. Approbation of the proposed method was carried out in the Gazebo virtual environment on the example of a garden of columnar apple trees with an area of several hectares, which includes more than 8000 trees. The final consolidated assessment of the proposed solution, averaged over all selected groups of tasks, was 74.6 %. The average proportion of trees missed in the experiment was: 7.8 %. According to the results of the experiment, the proposed solution allows not only to successfully carry out the tasks of fertilizing large agricultural facilities in a continuous mode of operation, but also to carry out autonomous identification of potential zones where fertilization is required.

FROST RESISTANCE OF THE COLUMNAR APPLE TREE THE METHOD OF DIRECT FREEZING

Frost stress strongly affects the spatial distribution of plants. Among various weather hazards, frost causes the greatest economic losses in agriculture. Among various environmental hazards, it is frost that causes the greatest economic losses in agriculture. Although frost severely limits life forms and creates enormous economic losses, it has not been studied as thoroughly as other biotic or abiotic stresses. Frost resistance can be affected by many factors, including microclimate, soil condition, plant height, but they must be studied in a complex. The purpose of the research was to select frost-resistant cultivars and hybrids of the columnar apple tree under the conditions of the Forest Steppe of Ukraine. The research was carried out during 2021–2022 at the V.L. Symyrenko Department of Horticulture of the National University of Life and Environmental Sciences of Ukraine. The experimental basis for conducting research was the columnar apple tree plantations of the Training Laboratory «Fruit and Vegetable Garden». Frost resistance was determined during the period of deep rest by the method of direct freezing of one-year increments. Freezing was performed in the laboratory of plant physiology and microbiology of the National Academy of Sciences of Ukraine. In the researched plantations, when the test samples were frozen at temperatures of -25 and -30 °C during deep rest, different resistance of varieties and shoot parts to low temperatures was found. In all cultivars and hybrids of columnar type apple trees, the apical bud and generative buds were the most vulnerable, and the tissues of the middle and upper part of the shoot were the most resistant to frost. The damage index during general freezing was the lowest in the cultivars Valuta’, Sparta’, Favoryt’, Bilosnizhka’, as well as in the hybrids 9/110 Mykhailivske’, 11/15(2)’ and 9/78 Viktoriia’; it was the largest in the Bolero’ cultivars. Freezing of experimental samples at temperatures of -25 and -30 °C did not result in frostbite, critical for plants. All studied cultivars and hybrids of columnar apple trees are recommended for further research and production. The obtained results will be interesting for both experienced gardeners and amateur gardeners who plan to grow columnar apple trees in their garden.

Influence of Variety on Total Polyphenols Content and Antioxidant Activity in Apple Fruits (Malus domestica Borkh.)

Recently, an increasing interest in fruits and vegetable eating has been noticed in particular through epidemiological and biochemical studies pointing to their health benefits for human health. Specifically, apples (Malus domestica Borkh.) are one of the most frequently consumed fruits. Therefore, the current study aimed to compare the total polyphenols content (TPC) and antioxidant activity (AA) of apple fruits from different columnar apple trees growing in experimental conditions. For this purpose, fruits of 7 apple cultivars obtained from the Botanic Garden (Slovak University of Agriculture, Slovakia; vegetative season 2019/2020) were analysed. Among them, four green-yellow cultivars: Golden Delicious, Granny Smith, Goldcats, Rondo; one green cultivar with red spots: Kordona; one red cultivar: Redcats, and one pink cultivar: Pompink, were used. Method using the Folin-Ciocalteu reagent was applied to quantify TPC, and radical scavenging activity of the samples was measured with 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavengers. Total polyphenols content (mg GAE.g-1 dry weight) ranged from 2.92 ±0.31 (cv. Pompink) to 9.02 ±0.32 (cv. Granny Smith), whereas statistically significant differences (p <0.05) were recorded between all analysed cultivars except for Rondo (5.07 ±0.44) and Kordona (4.18 ±0.35) cultivars as compared to Redcats (4.96 ±1.06) one. As with TPC, the lowest values for AA were observed in the Pompink cultivar (35.03 ±3.49 %) and, conversely, the highest ones in the cultivar Granny Smith (88.55 ±4.25 %). These results suggest that the values for TPC and AA in apple fruits are strongly influenced depending on the apple cultivars. From this aspect, upon achievement of this survey, and employing more samples, it will be possible to create a comprehensive overview of the antioxidant properties of apple fruits with the possibility of their application in the food industry to develop innovative products with added value.</p&gt

Evaluation of Priokskoe columnar apple variety from All-Russian Research Institute of Fruit Crop Breeding

The use of adaptive, scab-immune, stable-fruiting columnar apple tree varieties of domestic selection enhances profitability of commercial horticulture for a higher competitive power of national agricultural market. The diversity of columnar varieties remains little, yet offering a promising line of selection given a rising interest in this form of apple tree. The research aimed to comprehensively assess the economic and biological potential of the Priokskoe columnar variety to produce recommendations on its introduction in home and industrial gardening. A number of promising selected and elite genotypes, as well as five cultivars (Priokskoe, Poeziya, Vostorg, Orlovskaya Yeseniya, Girlyanda) have been identified from the extensive hybrid fund of columnar apple trees established at the All-Russian Research Institute of Fruit Crop Breeding for over 40 years. Priokskoe was the Institute’s first early-fruiting columnar variety starting at the third year post-inoculation on low-medium vigour rootstock. Average yield at planting density 14,000 plants/ha on dwarf stock 62-396 makes 49.1 t/ha and 78.3 t/ha — in the crown of skeleton-forming stock 3-17-38 at planting density 3,333 plants/ha. Priokskoe is a strong-vigour category among columnar varieties. A 7-year tree height on dwarf rootstock 62-396 was 217.3 cm, a crowned tree height on stem stock 3-4-98 — 281.7 cm. The variety’s winter hardiness is sufficient for its cultivation in the Middle Chernozem zone at no risk of irreversible winter loss. The Rvi6 gene-conditioned scab immunity enables improvement of the orchard phytosanitary situation via reduced chemical burden. The adaptability, economic and biological traits of the Priokskoe columnar variety ensure it a worthy rating among the current apple tree assortment recommended for intensive industrial horticulture.

Influence of mineral fertilizers on potash nutrition and productivity of columnar apple

The columnar form of apple tree is promising for growing in super-intensive orchards. The mineral nutrition study of apple tree with columnar crown is relevant due to high density of tree planting. The article presents the study results on the effect of mineral fertilizers on potash nutrition and the yield of columnar apple tree. The experiments were carried out in an experimental orchard located in the forest-steppe zone of the Central Russian Upland (Oryol region). The soil of the orchard is loamy haplic Luvisol with a high content of organic matter. Fruit plantations are represented by columnar apple trees of Poezia variety on 62-396 rootstock planted in 2016. Urea ((NH2)2CO) and potassium sulfate (K2 SO4) were used as fertilizers in doses of N60K80; N90K120; N120K160 which were introduced in early spring. The content of exchange potassium in the soil was determined annually in layers (0-20 cm and 20-40 cm), the concentration of potassium in leaves and fruits, yield. The use of fertilizers contributed to an increase in the exchange potassium content in the soil both in the 0-20 cm layer (45 - 53%) and in the 20-40 cm layer (18-31%). The amount of potassium in leaves and fruits also increased. However, potassium concentration in the leaves (0.77 … 0.95% dry matter) remained significantly below the optimum (1.5% dry matter). A significant increase in the average fruit weight was revealed in options N90K120 and N120K160.

The assessment of field resistance to scab and winter resistance of columnar apple trees in the Samara Region

The research was conducted from 2006 to 2019 in the garden of Research Institute of Horticulture and Medicinal Plants Zhigulevskie Sady in the village of Malaya Tsarevshchina of Krasnoyarsk District of the Samara Region on 14 (0,432 ha), 43 (0,1 ha), 44 (0,05 ha) and 47 (6,8 ha) areas. On the 14th area, to accelerate flowering, fruiting, pollen collection and hybridization, in the springs of 2007, 2009 and 2012, parent varieties-donors of immunity were grafted to scab of domestic and foreign selection in the crown of young fruit-bearing trees of the Northern synapsis. Hybrid seeds obtained by crossing these varieties with local varieties were sown on the seedling plot (in a new plantation) and tested for scab resistance at an early age (from 2 years old). Scab-resistant hybrids were culled, and resistant hybrids were replanted in the breeding garden on the 47th area and tested for winter resistance separately after low-temperature stress in the freezer and in the field. The authors have identified columnar elites resistant to scab, which are superior in winter resistance to the local zoned coastal variety Kutuzovets, zoned variety Northern synapsis and common Antonovka. Apple trees with a columnar crown type of local selection in Research Institute of Horticulture and Medicinal Plants Zhigulevskie Sady with a high field resistance to scab, immunity, winter resistance and other varietal advantages will contribute to the improvement of orchards (amateur, farm, industrial) and import substitution of fruit products in the Samara Region of Russia.

The apple columnar gene candidate MdCoL and the AP2/ERF factor MdDREB2 positively regulate ABA biosynthesis by activating the expression of MdNCED6/9.

MdCoL, which encodes a putative 2OG-Fe(II) oxygenase, is a strong candidate gene for control of the columnar growth phenotype in apple. However, the mechanism by which MdCoL produces the columnar trait is unclear. Here, we show that MdCoL influences abscisic acid (ABA) biosynthesis through its interactions with the MdDREB2 transcription factor. Expression analyses and transgenic tobacco studies have confirmed that MdCoL is likely a candidate for control of the columnar phenotype. Furthermore, the ABA level in columnar apple trees is significantly higher than that in standard apple trees. A protein interaction experiment has showed that MdCoL interacts with MdDREB2. Transient expression and electrophoretic mobility shift assays have demonstrated that MdDREB2 binds directly to the DRE motif in the MdNCED6 and MdNCED9 (MdNCED6/9) gene promoters, thereby activating the transcription of these ABA biosynthesis genes. In addition, a higher ABA content has been detected following co-overexpression of MdCoL-MdDREB2 when compared with the overexpression of MdCoL or MdDREB2 alone. Taken together, our results indicate that an interaction between MdCoL and MdDREB2 promotes the expression of MdNCED6/9 and increases ABA levels, a phenomenon that may underlie the columnar growth phenotype in apple.

Screening of apple genotypes with the columnar growth habit using control markers

One of the approaches to intensify horticulture is to introduce cultivars with an unusual canopy into commercial production. Such plants can be columnar Apple trees. In modern breeding, there is a trend to create cultivars with a compact canopy. In such orchards, it is reduced to a minimum the cost for pruning, harvesting, and protection against pest and disease, which are the main expenses in apple orchards with a traditional canopy. The use of molecular markers linked to columnar growth habit allows us to identify a physiological sign at an early stage of growth: in the juvenile period. The assessment of apple cultivars and hybrids was carried out at the I. V. Michurin Federal Scientific Centre in 2015-2018. Four markers were used in the research: Mdo. chr 10.12, C18470-25831, 29f1, and jwlr to identify plants with the columnar growth habit gene (Co). The use of various DNA markers made it possible to establish that not all of them are well linked to the Co gene. In the research process, primers were identified for markers 29f1 and jwlr, which reliably allowed us to identify plants with columnar growth habit at the juvenile stage, which will significantly reduce the breeding process.

Діагностика функціонального стану рослин колоноподібних сортів яблуні

Study of the function al the apparatus state of plants of six sorts of columned apple-tree was undertaken an in the Laboratory of Plant Physiology and Microbiology of the Institute of Horticulture of the National Academy of Sciences of Ukraine by means of portable device of " Floratest". Indexes that represent motion of process of photosynthesis in the letter of plants are certain.By change of IFH (fluorescence induction of chlorophyll) leaves characterized the efficacy of passing light phases of photosynthesis and photochemica l processes of the dark phase; for changes in the parameters of IFH, their small variability in time in the leaves of the columnar apple trees was established.A comprehensive analysis of functional parameters showed a high stability of photosynthetic proce sses in the leaves of all colonic apple varieties. The comparative analysis of the parameters of IFH leaves did not reveal the negative influence of the complex of external environmental factors on the activity of reaction centers and the effectiveness of dark photochemical processes.A decrease of 8-35% of inactive reactive centers of FS2 in the third decade of July was detected compared to the beginning of this month. The efficacy of the light phase of photosynthesis in the third decade of July in the leav es of colonic apple varies not significantly with respect to similar indicators obtained in the first decade.The stability of the light phase of photosynthesis in relation to the dark photochemical processes in plants and the sufficiently high adaptive pot ential of the investigated varieties to the conditions of cultivation, as well as their high potential of productivity, were noted.

Constitutive Expression of an Apple FLC3-like Gene Promotes Flowering in Transgenic Blueberry under Nonchilling Conditions.

MADS-box transcription factors FLOWERING LOCUS C (FLC) and APETALA1 (AP1)/CAULIFLOWER (CAL) have an opposite effect in vernalization-regulated flowering in Arabidopsis. In woody plants, a functional FLC-like gene has not been verified through reverse genetics. To reveal chilling-regulated flowering mechanisms in woody fruit crops, we conducted phylogenetic analysis of the annotated FLC-like proteins of apple and found that these proteins are grouped more closely to Arabidopsis AP1 than the FLC group. An FLC3-like MADS-box gene from columnar apple trees (Malus domestica) (MdFLC3-like) was cloned for functional analysis through a constitutive transgenic expression. The MdFLC3-like shows 88% identity to pear’s FLC-like genes and 82% identity to blueberry’s CAL1 gene (VcCAL1). When constitutively expressed in a highbush blueberry (Vaccinium corymbosum L.) cultivar ‘Legacy’, the MdFLC3-like induced expressions of orthologues of three MADS-box genes, including APETALA1, SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1, and CAL1. As a consequence, in contrast to the anticipated late flowering associated with an overexpressed FLC-like, the MdFLC3-like promoted flowering of transgenic blueberry plants under nonchilling conditions where nontransgenic ‘Legacy’ plants could not flower. Thus, the constitutively expressed MdFLC3-like in transgenic blueberries functioned likely as a blueberry’s VcCAL1. The results are anticipated to facilitate future studies for revealing chilling-mediated flowering mechanisms in woody plants.

A root-localized gene in normal apples is ectopically expressed in aerial parts of columnar apples

The columnar apple ‘McIntosh Wijcik’, which is a mutation of ‘McIntosh’ shoots, has short internodes, thick stems, upright growth, poor lateral branches, and increased spur density. These columnar traits are controlled by a single dominant gene known as Co. We previously identified a putative dioxygenase gene (designated as 91071) as a promising Co candidate (expressed in the shoot apices of ‘McIntosh Wijcik’). However, tissue expression and function of the 91071 gene in noncolumnar apples is still not clear. In this study, we used reverse transcription polymerase chain reaction to demonstrate that the 91071 gene is mainly expressed in the roots of noncolumnar apples, whereas it is also expressed in shoot apices and leaves of columnar apples. In situ hybridization revealed that the 91071 gene is expressed at the primordium of lateral roots and root tips of both noncolumnar and columnar apple trees and in the shoot meristem and leaf primordium in the columnar apple ‘McIntosh Wijcik’. Grafting experiments of noncolumnar scion onto columnar rootstocks revealed that the columnar growth phenotype is not transmissible from rootstock to scion. These results indicated that ectopic expression of the 91071 gene in aerial parts causes columnar growth, whereas the expression of the 91071 gene in roots does not produce columnar growth. Furthermore, transgenic apples overexpressing the 91071 gene showed larger median adventitious root length and higher median number of lateral roots than control apples. Our result suggests that the 91071 gene may be related to root development.

TOWARDS IDENTIFICATION OF THE GENE RESPONSIBLE FOR THE COLUMNAR PHENOTYPE OF 'MCINTOSH 'WIJCIK'' APPLE

The 'Wijcik' mutant of the apple cultivar 'McIntosh' shows columnar-type growth, characterized by altered branching and a thick stem. Instead of normal branches, spur-like branches are produced on 'Wijcik' trees, leading to apples produced close to the stem. Columnar-type growth is a desirable trait, as columnar apple trees need considerably less pruning compared to standard trees. Furthermore, apple picking and the application of chemicals is much easier on columnar trees. The genetic basis for columnar growth is a somatic mutation that results in dominant inheritance of the columnar growth trait. The columnar gene (Co) has been previously mapped on apple linkage group 10. Three adult segregating populations, with a total of 301 F1 plants, and two three-year old populations of 1,250 F1 plants were used for fine mapping of the Co region, using newly developed simple sequence repeat (SSR) markers that were designed based on the 'Golden Delicious' apple genome sequence. Co was found to cosegregate with SSR marker Co04R12 and the Co region was found to be delimited by SSR markers Co04R11 and Co04R13 corresponding to a genetic region of 0.56 cM and a genomic region of 393 kb in the 'Golden Delicious' genome. By using BAC libraries, we could identify the clones covering the Co region in 'McIntosh' and 'Wijcik'. This enabled us to sequence the complete Co region in both cultivars. Sequence comparison between 'McIntosh' and 'Wijcik' lead to the identification of a 1,956 bp insertion in 'Wijcik'. This work resulted in the development of a perfect marker for columnar growth for application in breeding, and, in the future, will result in better understanding of the physiological background of columnar growth and the availability of the Co gene for biotechnological applications to manipulate tree architecture.

Use of molecular markers for identification of genotypes of columnar apple trees

This paper presents the results of identification of columnar habit in apple trees using molecular markers 29f3 and 29f1. In the genome of varieties Strela, Teleimon, Kaskad, Geizer, Zelenyi Shum, Priok-skoe, and Gotika, an insertion determining the columnar crown habit in apple trees was identified in the near-gene region of the Co locus. This insertion is absent in the genome of noncolumnar apple tree varieties.

Predicting apple tree (Malus × domestica Borkh.) canopy architecture: phytohormone balance in juvenile hybrids

Apple tree (Malus × domestica Borkh.) is one of the most widespread and economically important fruit trees. Productivity and economic effect of apple orchards depend on many strongly related factors, one of them being tree canopy architecture, which determines fruit bearing and demand for pruning. Main apple canopy architecture topics are related to application of growth regulators, fertilizers, studies of shoot development and pruning, and environmental influence while physiologic aspects are studied less. Phytohormones play a major role in controlling many physiological processes of plant growth and development. Different amounts of phytohormones are found in the shoots of apple trees depending on their canopy architecture. However, information about phytohormones and their ratio in juvenile orchard plants is insufficient. Our goal was to identify phytohormones related to apple canopy architecture and to evaluate their usage as biochemical markers in predicting future canopy ideotype of apple seedlings in the first year of growth. It was established that large amount of auxin and high auxin to zeatin ratio are specific to columnar apple trees and they can be used as biochemical markers in juvenile phase. These amounts and ratios are similar in juvenile and cropping columnar apple trees, so phytohormone amount and ratio is independent of tree development stage. It is possible to select columnar apple hybrids in the first year of growth, thus reducing breeding expenses.

Evidence for regulation of columnar habit in apple by a putative 2OG‐Fe(II) oxygenase

Understanding the genetic mechanisms controlling columnar-type growth in the apple mutant 'Wijcik' will provide insights on how tree architecture and growth are regulated in fruit trees. In apple, columnar-type growth is controlled by a single major gene at the Columnar (Co) locus. By comparing the genomic sequence of the Co region of 'Wijcik' with its wild-type 'McIntosh', a novel non-coding DNA element of 1956 bp specific to Pyreae was found to be inserted in an intergenic region of 'Wijcik'. Expression analysis of selected genes located in the vicinity of the insertion revealed the upregulation of the MdCo31 gene encoding a putative 2OG-Fe(II) oxygenase in axillary buds of 'Wijcik'. Constitutive expression of MdCo31 in Arabidopsis thaliana resulted in compact plants with shortened floral internodes, a phenotype reminiscent of the one observed in columnar apple trees. We conclude that MdCo31 is a strong candidate gene for the control of columnar growth in 'Wijcik'.

Tracing a key player in the regulation of plant architecture: the columnar growth habit of apple trees (Malus × domestica)

Plant architecture is regulated by a complex interplay of some key players (often transcription factors), phytohormones and other signaling molecules such as microRNAs. The columnar growth habit of apple trees is a unique form of plant architecture characterized by thick and upright stems showing a compaction of internodes and carrying short fruit spurs instead of lateral branches. The molecular basis for columnar growth is a single dominant allele of the gene Columnar, whose identity, function and gene product are unknown. As a result of marker analyses, this gene has recently been fine-mapped to chromosome 10 at 18.51-19.09Mb [according to the annotation of the apple genome by Velasco (2010)], a region containing a cluster of quantitative trait loci associated with plant architecture, but no homologs to the well-known key regulators of plant architecture. Columnar apple trees have a higher auxin/cytokinin ratio and lower levels of gibberellins and abscisic acid than normal apple trees. Transcriptome analyses corroborate these results and additionally show differences in cell membrane and cell wall function. It can be expected that within the next year or two, an integration of these different research methodologies will reveal the identity of the Columnar gene. Besides enabling breeders to efficiently create new apple (and maybe related pear, peach, cherry, etc.) cultivars which combine desirable characteristics of commercial cultivars with the advantageous columnar growth habit using gene technology, this will also provide new insights into an elevated level of plant growth regulation.