Edīte Kaufmane and Laila Ikase
Edīte Kaufmane, Māra Skrīvele and Laila Ikase
In all times, fruit trees for family use have been grown at Latvian farms. Yet these fruits obtained market value only after the land ownership reform in 19th century. This facilitated rapid area increase of different fruit crops, allowing supply with fruits not only the local market, but also for export to the largest cities of Russia. Especially fast development of fruit-growing was observed during the first independent republic (1919–1940). The demand for planting material increased, and plants were imported from Western Europe. Choice of unsuitable cultivars and rootstocks was the main reason of the massive orchard area loss during the following severe winters. After the Second World War, the Soviet powers supported only the establishment of large orchards for processing needs, 200-300 ha, which were unsuitable for the Latvian climate and terrain. At the same time, numbers of allotment gardens rapidly increased and part of their produce was sold also on the market. After regaining of independence and private property, interest in fresh fruit and berry production for market, as well as processing, renewed. It was hindered by lack of continuity in experience and knowledge. Diversity of terrain, soils and climate all demand considerate choice of suitable orchard location and cultivars. Direct use of foreign experience often led to failure. At present, development of the fruit industry is most of all hindered by lack of qualified specialists of different levels, which does not allow to establish an appropriate consulting system. Cooperation of growers for easier marketing also is developing too slowly. Insufficient economic and market research does not allow to balance the demand with increase of plantation area, especially for large-scale processing and export, so strategic guidance of the fruit industry is not possible. Development of fruit-growing is hindered also by a lack of continuous long-term support to horticultural science. As a result of research by the Institute of Horticulture: 1) new local breeding fruit crop cultivars were obtained and recommended for commercial orchards; variety testing including growing technologies was initiated in different regions of Latvia; 2) monitoring of harmful and favourable organisms was conducted in plantations, with development of a system for prognosis and control; and 3) research results were transferred to growers through practical recommendations, publications, seminars and demonstrations.
Edīte Kaufmane, Ilze Grāvīte and Laila Ikase
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.
The most widely used rootstocks are seedlings of Prunus cerasifera Ehrh. ssp. divaricata C.K. Schneid., which is more hardy that the common myrobalan plum. These rootstocks have good compatibility with most cultivars except gages, and are adapted to different soil types and are disease tolerant. Their drawback is a long growth season which reduces winter-hardiness of grafted cultivars. Also, they tend to form suckers around the stem. A hardy seedling PU-20651 (P. salicina ssp. ussuriensis × P. cerasifera) was bred at the Institute, which was shown to slightly reduce tree vigour. Testing of several Western European and Russian rootstocks did not result in their introduction into production. Trials are presently being carried out with size-reducing root-stocks originated from cultivar Wangenheim VVA-1, Weiwa, S766, and M633.
Commercial production of plums in Latvia is relatively small, as the area of orchards is the smallest among fruit trees. Plums are grown mostly for fresh consumption, with a small part for jams, yoghurt, and ice-cream additives. Fruits are sold mostly in small shops, markets and at farms. The main reason is the climate, which allows growing of a limited range of cultivars that tolerate the –30 °C winter temperatures in some years (about every five years). About 20 cultivars are grown commercially; the share of the six most popular plum cultivars is 69% of the total plum production. In recent years, plantations of new cultivars developed at our Institute have expanded, especially regarding the early ripening cultivar ‘Ance’.
Ilze Grāvīte and Edīte Kaufmane
The aim of the study was to determine the suitability of growing plum cultivars and hybrids of German origin in Latvian conditions. In the trial the plum cultivars and hybrids were planted at the Latvia State Institute of Fruit Growing (now, Institute of Horticulture) in spring 2008. Six W. Hartmann genotypes (cultivars ‘Tipala’, ‘Tegera’ and ‘Haganta’, and hybrids H-5102, H-3753, and H-3690) from Hohenheim University were included in the study. Prunus cerasifera was used as rootstock. The parameters evaluated were: beginning of flowering, ripening time, average yield (kg per tree), cumulative yield (kg), and average fruit weight from 2012 to 2016, and content of soluble solids from 2014 to 2016. In addition, self-fertility was evaluated in 2015 and 2016 for three cultivars and one hybrid. The winter of 2010/2011 was unfavourable, as plum orchards and most plum cultivars in Latvia suffered winter damage, but cultivars and hybrids in the trial were without damages. Significant damages were not observed in further years. Average flowering time in the four-year period for all cultivars and hybrids was the 1st or 2nd decade of May, harvest time was from the 1st decade of August to the 3rd decade of September. The earliest was hybrid H-3690, and the latest was cv.’Haganta’. The most productive was hybrid H-3690, which gave 42 kg in the 3rd year of yield and had the most rapid rise in yields. ‘Haganta’ had the biggest fruits (50 to 60 g) and highest content of soluble solids (17-18 Brix%). Self-fertility level was 40% for ‘Tegera’, 17.4% for ‘Haganta’, 14.5% for H-3690 and 0% for ‘Tipala’. Evaluation of all analysed parameters showed that ‘Tegera’ could be recommended for Latvian growers thanks to good winter hardiness in the research period. ‘Haganta’ is recommended only for warmer regions in Latvia. Hybrid H-3690 will potentially be useful for Latvian growers.
Ilze Grāvīte, Edīte Kaufmane, Laila Ikase and Edgars Cirša
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.
Vitālijs Radenkovs, Edīte Kaufmane, Edgars Rubauskis and Dalija Segliņa
Plums are one of the most popular, perspective and frequently consumed fruits in Latvia. Plums are typical climacteric fruits, respiration occurs during ripening. Respiration rate is mainly associated with synthesis of autocatalytic ethylene and depends of the cultivar of fruits. Metabolic processes occurring during plum storage cause changes in fruit quality. The aim of this work was to determine the effect of treatment by 1-methylcyclopropene (1-MCP) on physical and chemical characteristics and sensory qualities of five plum (Prunus domestica L.) cultivar fruits (‘Adele’, ‘Sonora’, ‘Victoria’, ‘Stanley’, ‘Minjona’) during four weeks of storage in a cool store-room at temperature 3±1 °C. The following analyses were performed to evaluate quality changes during storage: mass loss, concentration of total acids and soluble solids, firmness, and sensory qualities (colour, flavour, acidity, sweetness, firmness, and stone adherence). The study showed that treatment with 1-MCP had positive effect on fruit firmness during four weeks of plum storage, and there were significant differences in the content of total acids and soluble solids between 1-MCP-treated and control plum fruits. The results indicated that there were no significant differences in flavour (aroma) and colour between treated and untreated plum fruits, while 1-MCP-treated fruits were firmer and more sour.
Edīte Kaufmane, Māra Skrīvele, Edgars Rubauskis, Sarmīte Strautiņa, Laila Ikase, Gunārs Lācis, Dalija Segliņa, Inga Moročko-Bičevska, Silvija Ruisa and Ilze Priekule
Development of fruit growing and fruit science in Latvia has always been closely linked to the development of the whole country. After the founding of the independent Latvia state in 1918, fruit growing developed rapidly. Although in the Soviet times the situation was not favourable for quality fruit growing, research and breeding continued with good results. After Latvia regained independence, private land property rights were restored, and interest in intensive orchard establishment and growing technologies increased rapidly, which demanded change in the research focus. At present, the Latvia State Institute of Fruit-Growing is the leading institution in this field, working in cooperation with Pūre Horticultural Research Centre, Latvian Plant Protection Research Centre, Institute of Agrobiotechology, and Faculty of Food Technology, Latvia University of Agriculture, Laboratory of Plant Mineral Nutrition, Institute of Biology, University of Latvia. Research is carried out in the following directions: breeding and cultivar evaluation; genetics and molecular biology; plant pathology and entomology; orchard management; experimental processing and storage.