Evaluation of Estonian apple cultivars and hybrids in Latvia

Estonian apples have always been popular in Latvia. At present, ‘Tiina’ is widely grown commercially as well as in home gardens, and ‘Liivika’ is promising for organic and home orchards. A number of new Estonian apple cultivars and hybrids have been screened in 1990–2020. Several new selections by breeder Kalju Kask (Polli) are included in field trials at Institute of Horticulture - ‘Aule’, ‘Kastar’ and KK 201-2 (‘Karlote’) since 2011, ‘Kersti’ since 2014, KK 5-16 (‘Kelin’) with scab resistance gene Rvi6 and KK 2812 since 2015. Their trees were planted on dwarfing rootstock B.9 as one-year-old whips at distances 1.5×4 m, in 3 to 5 replications with 2 or 1 trees. Commercial cultivars ‘Auksis’, ‘Antei’ and ‘Zarya Alatau’ were used as controls. The highest productivity had ‘Aule’ and ‘Kastar’, the best fruit quality - ‘Aule’ and ‘Kelin’. ‘Aule’ has been highly esteemed also by some Latvian farmers. Fruits of ‘Kelin’ had the best storage, which is crucial for a cultivar’s commercial success in Latvia. On the other side, ‘Kersti’ proved to be unsuitable for Latvian conditions, having very strong tree vigour and low yields. ‘Kastar’ showed a high tendency to fruit cracking at calyx, while KK 201-2 and KK 2812 had irregular or low yields. Of newer acquisitions, scab resistant (gene Rvi6) ‘Virve’ and KK 4-11 show good preliminary results and have been propagated for trials on dwarfing rootstocks. Productivity, tree characteristics, fruit quality traits and taste panel evaluation of Estonian apples in Latvia are discussed

Evaluation of the main biological and production traits of Latvian apple cultivars in the conditions of Central Russia

Apple selections of Latvian breeding were evaluated in the Central zone of Russia since 1980, in total 32 cultivars and hybrids. After long-term evaluation, the following can be recommended for use in breeding of scab resistant cultivars with high quality fruits - ‘Dace’ (gene Rvi6), ‘Arona’, and good storage - ‘Edite’ (Rvi6), ‘Forele’, ‘Olga’, ‘Маdоna’, for breeding of early cultivars - ‘Roberts’ and DI-93-4-8, both resistant to scab (gene Rvi6) and fruit rots. Cultivars and hybrids with the best cold resistance of vital tissues were selected by artificially modelling winter-hardiness components − early colds (1st component) and mid-winter colds up to -38 °C (2nd component), showing reversible damages not exceeding 2.0 points: ‘Daina’, ‘Ella’, ‘Atmoda’, ‘Gita’, ‘Saiva’, of which the last 3 maintained high hardiness of bark, cambium and xylem with slight increase of bud damages also at -40 °C. Cultivars ‘Daina’ and ‘Ella’ showed resistance of buds and vital tissues on the level of ‘Antonovka’ after modelling a thaw with following freezing to -25 °С (3rd component), which suggests tolerance to fluctuating winter temperatures. These cultivars demonstrated good adaptation to different environment conditions and may be considered in breeding of new adaptive apple cultivars with high fruit quality

Prunus cerasifera Ehrh. un tas starpsugu hibridi ka jauns genu avots plumju selekcijai Latvija

Summary in English and RussianAvailable from Latvian Academic Library / LAL - Latvian Academic LibrarySIGLELVLatvi

Plum Research and Growing in Latvia

Plums have been commercially grown in Latvia since the 19th century. Plantations expanded especially in the 1920s–1930s. At that time, many cultivars were introduced, mostly from Western Europe. After the severe winters of 1939/40, 1941/42, 1955/56, and 1978/79, the plum orchard area significantly decreased because of a lack of winter-hardy cultivars. For this reason, cultivars from Russia, Belarus, and Estonia were introduced. Among the old landraces, highly winter-hardy ‘Latvijas Dzeltenā Olplūme’ is still important. Previously it used to be productive and had good fruit quality. Unfortunately, nurseries often propagated the hardiest clones, which lacked productivity. As Latvian consumers love yellow plums, at present breeding and propagation of productive clones from old orchards is ongoing. In the mid-20th century, active plum breeding started in Latvia, crossing hardy genotypes with high quality donors. From this period ‘Lāse’ and ‘Minjona’ are still grown. Since the 1980s, plum breeding has been undedrtaken at the Institute of Horticulture. The crossing work in plums concentrated on the hexaploid group, aiming to combine large fruit size with good flavour, different time of ripening (in particular, early to medium late) and and good winter-hardiness. New cultivars include ‘Sonora’, ‘Ance’, and ‘Adelyn’, which have good quality, and productivity 20–30 kg per tree, and in some years up to 70 kg per tree

Inheritance of Apple (Malus × domestica (L.) Borkh) Resistance against Apple Scab (Venturia inaequalis (Cooke) Wint.) in Hybrid Breeding Material Obtained by Gene Pyramiding

Apple scab caused by the pathogenic fungus Venturia inaequalis causes significant damage to apples. The creation of apple-scab resistant varieties is considered an alternative to pesticide-based management. To evaluate R gene inheritance, 862 apple hybrid samples were analyzed and divided into populations depending on the resistance genes (Rvi6 and Rvi5) present in the parents’ genotypes and their combinations. The field evaluation was carried out in 2016–2018 using the international VINQUEST scab evaluation methodology, but the genes were identified using specific scab resistance-gene molecular markers. Parent plants were genotyped using 22 SSR markers. The study determined that the field resistance of apple scab is influenced not only by the resistance genes present in the genotype but also by the genetic background of the apple cultivar, the tree’s general health status and resistance to other diseases. It was found that the apple scab resistance genes Rvi6 (Vf) and Rvi5 (Vm) are inherited according to Mendelian laws, and when both genes are pyramided in offspring, they are inherited as separate genes. In general, the inheritance of both genes in the offspring is not a determining factor for apple field resistance, as field resistance to scab is influenced by a combination of several factors

Inheritance of Apple (<i>Malus</i> × <i>domestica</i> (L.) Borkh) Resistance against Apple Scab (<i>Venturia inaequalis</i> (Cooke) Wint.) in Hybrid Breeding Material Obtained by Gene Pyramiding

Apple scab caused by the pathogenic fungus Venturia inaequalis causes significant damage to apples. The creation of apple-scab resistant varieties is considered an alternative to pesticide-based management. To evaluate R gene inheritance, 862 apple hybrid samples were analyzed and divided into populations depending on the resistance genes (Rvi6 and Rvi5) present in the parents’ genotypes and their combinations. The field evaluation was carried out in 2016–2018 using the international VINQUEST scab evaluation methodology, but the genes were identified using specific scab resistance-gene molecular markers. Parent plants were genotyped using 22 SSR markers. The study determined that the field resistance of apple scab is influenced not only by the resistance genes present in the genotype but also by the genetic background of the apple cultivar, the tree’s general health status and resistance to other diseases. It was found that the apple scab resistance genes Rvi6 (Vf) and Rvi5 (Vm) are inherited according to Mendelian laws, and when both genes are pyramided in offspring, they are inherited as separate genes. In general, the inheritance of both genes in the offspring is not a determining factor for apple field resistance, as field resistance to scab is influenced by a combination of several factors

Influence of Different Training Systems on the Beginning of Domestic Plum Production and Yield

All growers prefer to obtain a first harvest as soon as possible. The aim of this study was to identify an effective tree training system for new Latvian plum cultivars, which provides the highest yield and fruit quality. The trial was established in 2012 at the Institute of Horticulture (formerly Latvia State Institute of Fruit-Growing) and included cultivars ‘Ance’, ‘Adelyn’, and ‘Sonora’; and the controls ‘Victoria’ and ‘Jubileum’. Planting distances were 4 × 2.5 m, and the rootstock was Prunus cerasifera. Tree training was done using four systems: two systems with branch bending (Heka espalier and spindle); and two systems without bending (standard (round) and flat crown). Evaluation of average fruit weight and yield per trunk cross section area (TCSA) was done from 2015 to 2017. The Heka espalier and spindle systems had first yield in 2015, but systems without bending had first yield only in 2016. Average yield per TCSA was significantly higher for the Heka espalier system (0.49 kg·cm−2) than for the spindle system (0.24 kg·cm−2), standard crown system (0.17 kg·cm−2), and flat crown system (0.30 kg·cm−2). Cultivar ‘Victoria’ had the highest yield among all systems. Average fruit size showed the same results: the biggest fruits were obtained with the Heka espalier system, and the smallest for systems without bending in the standard crown

Use of apple tree gene pool to create adaptive cultivars with high quality fruits

The apple tree gene pool was evaluated by resistance to adverse winter conditions based on the analysis of weather data for 50 years. 70% of winter-hardy and highly winter-hardy cultivars were revealed in the group of traditional local cultivars. Many local Central Russian cultivars are widely used in the breeding of new winter-hardy cultivars in central Russia, the Volga region, the Urals, Siberia, the Altai, the Far East and the south of the country. Positive results were obtained by using cultivars obtained from stepped crossbreeding, combining a complex of valuable qualities (winter resistance, immunity to scab, high qualities of fruits) in selection. On the basis of damaging factors' modeling, resistance to -38° C temperature and resistance to frost after thaw were confirmed in most VNIISPK breeding cultivars; winter-hardy cultivars with a resistance threshold -40°C: Vyatich, Orlovskiy partizan, Orlovskoye polesie, Zdorovye, Ministr Kiselev, Pamyat' Semakinu, Rozhdestvenskoye. Cultivars Idared, Golden Delicious, Granny Smith, Gala, Jonagold, Pink Lady, Fuji, Honeycrisp are recommended for use in breeding in combination with winter-resistant cultivars to create new high-quality apple tree cultivars with long keeping quality