CC BY
21AGRICULTURAL SCIENCES
EVALUATION OF ECOLOGICAL ADAPTABILITY POTENTIAL OF OLIVE (OLEA EUROPAEA L.)
CULTURE IN GEORGIA
Bobokasvili Z.
Associate Professor, PhD in Agricultural Sciences,
Maglakelidze E.
PhD in Agricultural Sciences,
LEPL Scientific-Research Center of Agriculture, Division of Fruit-growing Research, Marshal
Tbilisi, Georgia DOI: 10.5281/zenodo.6579798
ABSTRACT
The article presents the prospective for use of olive (Olea europaea L.) culture in scientific, selective and agricultural level, in Georgia. Due to climate change it is important to promote the production agricultural crops that has traditionally been cultivated under conditions of limited water availability. One of such promising cultivated plant is the olive. Olive crop production has a good perspective in Georgia. Olive culture represent a key agricultural system with high economic and environmental prominence. Great interest in this unique plant, which provides a good opportunity to improve the diversity of fruit assortment and the economic conditions of the country. The article discusses the factors that contribute to the development of olives and how to implement them.
We describe several old Georgia and introduced varieties have been chosen on the basis of good productivity, good fruit size and flavor and good storage and shelf life.
Keywords: fruit quality, country, variety, crop.
1. Introduction
Olive is a long-living perennial species with a wide geographical distribution, showing a large genetic and phenotypic variation in its growing area (Mousavi, et al., 2019) Olive cultivation dates back more than 6,000 years and it is still flourishing today, not only in its countries of origin, but now in most areas of the world. The olive tree has been a symbol of peace since ancient times. In addition to being a symbol of peace from the beginning, the olive tree was also considered a symbol of victory. The winner of the Olympic Games was crowned with an olive wreath. Olives were considered a precious tree in Greece. Olives are also mentioned in the Bible and the Qur'an. Both Christians and Muslims consider the olive tree to be a blessed plant from God. According to the Bible, when the great Flood ended and Noah sent a dove out of his ark with an olive branch on the earth (Maghlakelidze, 2017; Moriondo, et al., 2013; Mousavi, et al., 2019).
There are many opinions about the origin of olives. According to some researchers, it is from the Mediterranean countries, where it was spread in the forests before the origin of man, while some believe that the homeland of the olive is the Western Himalayas.
According to Mariela Torres et al. indicates that, "The geographic origin of cultivated olive (Olea europaea L.) can be traced to areas along the 54 eastern Mediterranean Coast in what are now southern Turkey, Syria, Lebanon, Palestine, and Israel. 55 Some records indicate that, at these geographic areas, olive trees have been cultivated since at least 56 3000 BC. Olive then spread widely around southern Europe, northern Africa, and the 57 Iberian Peninsula. Today, approximately 98 % of olives are cultivated in Mediterranean Basin 58 countries. Spain, Italy, and Greece together produce about 77 % of the world's olive oil.
Portugal, 59 Tunisia, Turkey, Morocco, Syria, and Egypt also have an important amount of production, but oil 60 yields are low per hectare in many instances and modern processing technology is underutilized".
Today, olive is a very important agricultural crop. World olive plantations occupy more than 11 million hectares, which allows to receive about 23 million tons of olives annually, and every year there is a significant increase in these indicators.
The world leaders in olive production are Spain with 6,559,884 tones followed by the Greece 2.343.383 tones, Italy 2.0921.175 tones, and Turkey 1.730.00 tones in based on the (FAOSTAT 2019).Almost in all countries in the world an increase in olive production is observed. An increase in production of olive, as well as profitability of its growing, depends on biological and economic properties of the cultivar. In fact, production is gradually rising in non-traditional producing countries such as Argentina, Australia, New Zealand, Chile, South Africa and the U.S.A.
The four main producers of olive oil are Spain (1.27 million tons), Italy (408,100 tons), Greece (284,200 tons) and Turkey (178,800 tons). The four leading producers of table olives are Spain (533,700 tons), Egypt (407,800 tons), Turkey (399,700 tons) and Algeria (178,800 tons). These figures are an average of the past six crops, according the IOC.
Olive production has good perspective in Georgia. Commercial cultivation of olive (Olea europaea L.) is available in Western and Eastern regions of Georgia, but main production region is East - South of Kakheti (where is located 95 % of Olive production in Georgia) gives the best quality product among those. The Basic variety is Gemlic, which is introduced from Turkey. Several hundred tons of fruits were harvested annually, to produce canned food, marinades and olive
oil (Chkhaidze,1998; Kvaliashvili, 2001; Ketskhoveli, et al., 1957; Tsulukidze, 1953).
This unique plant is of great interest with creates a good opportunity for diversify the assortment and improve the economic conditions of the country. At the beginning of the 20th century, olive growing was intensively practiced in Georgia. 60-78 tons of fruits were harvested annually, from which canned food, marinades were made and they were making olive oil. Rehabilitation and creating of olive production sector was started decade ago by initiative the companies "Georgian Olive "and" Geolive "s since 2010. Over than 1500 ha (2019 evaluation) of olive orchards was established in country within of these year (Ketskhov-eli, et al., 1957; Torres, et al., 2005; Agro biodiversity of Georgia, 2015).
2. Olive cultivation and nutritional value
Olive is a fruit crop with a high economic importance due to the nutritional, technological and commercial value of its fruits. The olive tree is now used for oil and canned-fruit production, with minor use of the wood for handcrafts. The leaves are used in medicine as herb tea, due to mainly their high phenolic compound content as oleuropein and hydroxytyro-sol, which are beneficial in nutrition and medicine (Agro biodiversity of Georgia, 2015; Connor, 2005; Hartmann and Panetsos 1961; Matesanz, et al., 2010).
The pulp of ripe fruits is 50 - 70% water, it also contains vegetable fats (6 - 30%), sugar (2 - 6%), protein (1 - 3%), fiber (1 - 4%), ash (0.6 - 1%). Fruits are rich in elements such as: sodium, potassium, magnesium, calcium, phosphorus, iron, copper, selenium, zinc. High-value nutrients are found not only in the pulp of olives of varying ripeness, but also in their bones, which are completely processed in the gastrointestinal tract (Bradley et al., 1961; Tognetti, et al., 2007; Zhukovsky, 1971).
The nutritional value of the olive stems from the fact that it has very little carbohydrate and is a great source of monounsaturates. This makes it a good element in a low-carbohydrate diet. Olives are a rich source of polyphenols, which are critical as our body's defense against cancer. Polyphenols have many good properties, and these elements, which are the reason for the taste and the smell of the olive, can also help as an anti-inflammatory.
Medical research has confirmed the value of olive oil. Olive oil is appreciated not only for its nutritional value but also as an integral part of the Diet. Olive oil is a good source of many beneficial nutrients and minerals. The oil is a good source of antioxidants and, as a special bonus, it greatly adds to the flavor of dishes. As it contains monounsaturated fat, it does not elevate the level of cholesterol in the body (Rapoport, 2014; Zeleke, et al., 2012).
Wild olive tree is known as 'acebuche' (Olea sylvestris). It was one of the first varieties of olive trees in the Mediterranean area and after several crosses and upgrades originated the existing variety Olea europaea (Rapoport, et al., 2012; Zeleke, 2014; Zeleke, at al., 2014).
Although the cultivation of olive tree has been extended to many other regions of the world, olive
fruits remain a typical Mediterranean crop, where they play an important role in diet of the people in the area as well as in their economy and culture (Nicotra, et al., 2015; Vavilov, 1935).
According to Rosa M. Seabra olea europaea is a highly variable species. This large number of olive cultivars is partially explained by the fact that olive plants can survive for a long time, thus retaining their genetic characteristics for thousands of years. Furthermore, open crossing between individuals, environmental pressure and its long history as a crop have resulted in numerous cultivars (Mailer, et al., 2010).
Speaking in general, soil and climate conditions of Georgia enables us to have a wide range of agricultural crops (GEOSTAT, 2019; Maghlakelidze, 2017). The agricultural land area is about 3 million hectares and 9% among those is cultivated by the perennial crops. The average yield per hectare of fruits is 3-4 tons from the 60 000 hectares of orchards. 25% of fruit orchards from total area is located in the Shida Kartli region (Tsulukidze, 1953).
Olive culture was famous and planted in Georgia several hundred years ago. With laurel plants on Mount Urta (West Georgia) olive trees are common. Also separate old Plants can be found in Chokhatauri, Senaki, In Khobi, Terjola, Akhali Athoni, Gurjaani and In Sighnaghi districts (Different regions of Georgia). There been the local varieties of olives: "Oturi", "Butko" (Canning direction) "Gorvala" (oil mime difficulties) and others. In Tbilisi, was very popular olive variety "Tbilisuri", which is only available now in Abkhazia (Western region of Georgia).
After cold winters of 1930th olives became rare crop to the Georgia. According of former SU planning economy Georgia began to cultivate other crops - In particular, tea and citrus fruits in western Georgia and apples and grape - Eastern Georgia.
In recent times, with the support of the Patriarch and the Georgian Diaspora, the olive culture is still alive returned to Georgia. On the revival of this culture the care was started 7 years ago by the companies "Georgian Olive "and" Geolive ". On 300 hectares (250 thousand olive trees) planted on a plantation. In the village of Sakobo, Signagi region (Eastern region of Georgia), an olive factory was opened for investments by the Dutch-Turkish.
3. Some biological properties and local varieties of olive culture
The olive plant is distinguished by its long shelf life. Prolonged life of plants is composed of several centuries, - specimens grow up to 1000 - 1600 years and get sick. In contrast to the other representatives of the fruiting trees, olives do not end up happy to enjoy even at the age of three. Up to 50 years of fertile fruit maturity, olives continue to increase their productivity every year. In the height olive culture can reach 10 -20 m, but in the modified plants it is necessary to regularly regulate the comfort of the well, because the growth of the tree rarely exceeds 5 - 10 m. Exercise in most cases stretched, often oval and wrong, abundantly leafed. The olive tree forms a very branched crown over a short, but rather thick, knobby and hollow trunk, and the smooth gray-
green bark, characteristic of young trees, cracks and takes on a dull dark gray, sometimes brownish-gray (Gucci and Fereres, 2012; Lavee,at al., 2012)
The leaves have lanceolate or oval shapes, they reach 4 - 10 cm in length and 1 - 3 cm in width.
During flowering, racemose inflorescences of 10-15 small, but very fragrant, four-petal flowers of white or cream color, pollinated by the wind, are formed.
The fruit is an oblong or ovoid, 0.7 cm to 4 cm long and 1 - 2 cm in diameter, drupe weighing 1 to 10 g. or even more according to the cultivar. . Fruit changes color according to maturity. The skin of fruit is green when immature and dark blue, blue-violet, black when ripe with sometimes many lenti-cels. The pulp of fruit becomes soft at the full maturity stage. The oil is present in all skin (pericarp), pulp (mesocarp) and the seed (endocarp). The tree bears fruit once a year (depending on the variety). After planting, the tree usually begins to bear fruit in the fourth or fifth year.
Productivity depends on the type of tree and growing conditions (. Lavee, at al., 2012; Lavee, 2014).
The root system of the olive tree develops depending on soil conditions, but the bulk of the adventitious roots is concentrated in the fertile layer, not deeper than 0.7 - 1 m. On loose soils, the main roots of the tree grow vertically, penetrating to a depth of 7 m, and in solid and on rocky ground, the root system is formed in the form of a superficial highly branched network. Although the taproot grows deep into the soil, the fibrous roots are shallow. Therefore, deep soil ploughing is not useful for olive groves, because fibrous roots grow closer to the surface, especially in clayey soil (Sanz-Cortes at al., 2002).
This feature of the plant explains its ability to withstand long (sometimes up to several months) dry periods.
According to Giorgi Svanidze, the founder of the Olive Company, Georgia can produce the highest quality olives and olive oil. Today's new plantations in different regions of Georgia, are cultivated mainly from varieties imported from Turkey. The introduced varieties growth of the tree 10-12 cm higher in Georgia. The skin of the fruit is thinner and the stone is smaller, which indicates the quality of the olives. According to world data, 4-5 kg of fruit produces about 1 liter of oil. In Georgia 1 liter of oil is obtained from 3 kg of olive fruit. This is a pretty good and impressive result (Maghlakelidze, 2017).
Unfortunately, the old varieties are no more exists, or is preserved in the form of separate trees.
Therefore, the primary task is to restore to olive varieties ("Tbilisuri", "Akhasheni", "Butko", etc.), which were distinguished by good adaptability and resistance in the conditions of Georgia.
Variety -"Tbilisuri". The origin is unknown. Found in New Athos, Sokhumi. (Western region of Georgia). It is also found in the form of unit trees in different regions of Georgia. The variety is characterized by resistance to pests and diseases. Tree
is high - 8-10 m, develops wide, rounded, a well-drained, well-leafed exercise. Characterized by abundant and regular growing. The average yield of per tree is 40 kg. Flowering in the second half of May. It is self-fertile. The fruit is medium-sized, weighing 3-5 g, rounded oval, symmetrical. The skin of the fruit is soft; After ripening dark in color, with shiny skin. The fruits ripen in November. Ripe fruit contains 60,5-72% oil. Used for canning (marinade) and to get oil.
Variety - „Oturi". The origin is unknown. Distributed in different regions of Georgia (New Athos, In Sukhumi, Terjola and Baghdad). The tree is characterized by rapid growth, usually is of medium height, develops a beautiful, open, strongly branched, often leafy exercise. Characterized by abundant and regular growing. Characterized by drought and frost resistance. Flowering time in late May. It is self-fertile. In the case of cross-fertilization, the yield increases significantly. Ripen in the second half of November. Fruit size is large - 9-14 g. oval, symmetrical. The skin of the fruit is soft, duke-blue in ripeness. Stone - small size. Oil content in the fruit -65-68%. The fruit is best for both canning and oil.
Variety - "Tolgomuri" - originated in the Caucasus. It was named after the village of Artvin district from Tolgomi. Mostly found in New Athos (Western region of Georgia). The tree is of medium height, develops a deciduous, branched, slender trunk. Characterized by medium to regular growth.Less resistant to pests and diseases. Flowering time in late May. To get a high yield requires a pollinator.The fruit is large. weighing 5-7g, rounded-inverted ovate, asymmetrical. The skin of the ripe fruit is tender. Covered with black wax snowflake. The stone is large in size. The fruits ripen time is in early November. The fruit is suitable for both canning and oil production. Content of oil in the fruit 70%.
4. Attitude towards environmental factors of olive culture
In addition to a sunny, warm and dry climate, olive trees prefer loose heavy or medium-structured, well-drained, lime-rich soils. They can also grow on rocky and shallow rocky soils, but prefer clayey-loam, sandy loamy, and loamy soil with a moderate moisture around the root zone. Heavy soils prone to stagnant moisture cannot be used to grow olives. The culture is quite undemanding to the level of soil fertility: it can also grow on poor lands with a reaction far from neutral (pH 8.5-9). If pH values are lower or higher, the quality and yield of olives decreases. The main reason for the weak development of olives in Western region of Georgia is the excessive rainfall and acid reaction of the soil. Olive is one of the few crops that can grow in saline conditions, therefore it is often grown on the sea coasts.
The soils of Kakheti (Easten region of Georgia are very diverse. Humus-carbonate clay soils are found on the slopes of Tsivgombori. In the lower zone - the gray soils of the forest. A large number of alluvial-carbonate and alluvial soils rich in potassium and phosphorus make it possible to produce high quality olive crops on such soils. In the south-
eastern part there are soils rich in black and chestnut humus. In the same zone there are also saline soils, which may be used after preliminary reclamation measures.
Soil degradation and desertification processes are intensive in Georgia, which leads to the reduction of a large area of agricultural land. Up to one million hectares of soil are affected by erosion processes of varying degrees (Vavilov,1935; Tsuluki-dze,1953; Maghlakelidze,2017) Climate change has a particular impact on soil degradation in Esten re-giom of Georgia. The soils of Kakheti region (Eaten Georgia) where olives culture are produced are quite dry and drought. Soil degradation is mainly caused by wind erosion and drought. We are mainly dealing with strong wind erosions and salinization of soils caused by irrigation. Soil salinity is often caused by excessive watering. Water erosion significantly reduces soil fertility. These problems are manifested in the transfer of the fertile soil lay (Denney and McEachern, 1983; Lavee, 2014).
Olive is a plant with requiring long hot summers and humid, cool winters. Its frost resistance averages 17-20 0C. Heat-loving, cannot adapt to wet conditions. Yield is also affected by lack of moisture. Trees also react badly to a decrease in temperature. Already at +3 -4 °C, you can observe the drying of the tips of their shoots. And frosts down to -7 - 10 °C can cause significant damage to the culture, causing the death of its vegetative part. Strong winds, especially together with low temperatures and excessive rainfall, are also detrimental to the development of olive trees. These factors must be taken into account when organizing olive cultivation (Borges, et al., 2017; Gucci, and Caruso, 2011).
The olive tree (Olea europaea) is a drought-resistant plant usually grown in areas with limited water resources. Some regions of Eastern Georgia characterized by scarce rainfalls, the irrigation could influence both the olive oil production and the olive oil quality (FAOSTAT, 2019).
Olive trees survive long dry summers without damage, resuming their vegetative activity only with the onset of rains. The lack of moisture still negatively affects the quality of the crop. It is especially critical during flowering, fruit formation and growth (Carr, 2013; Pierantozzi, at al., 2014).
Olives grow normally in Georgia, where the annual rainfall is 600-700 mm, In case of less precipitation, watering is necessary. Olives belong to heliophilic plants, so any shading has a depressing effect on them and significantly reduces the abundance of flowering. The sum of active temperatures requires 3500-4000°C for the ripening of fruits of early varieties. For late varieties - 4500-5000 0C the optimum temperature for flowering is 22-280C. Time of flowering, depending on the climatic zone, can occur from the end of April to the middle of June. Fruit ripening occurs 4-5 months after flowering. The fruit is horticulturally matured in October- November (OOC World Catalogue. 2000).
Climate change have led to several adverse events, such as: the increase of impoverished marginal land area, strengthening desertification process, significant deficit of irrigation water and permanent increase of erosive factors (ENVSEC, 2011; Tyler 2009 et.al; Walls, 2010). The factors mentioned above are also quite remarkable in Georgia, where more and more agricultural land stays uncultivated due to cataclysms caused by global warming, such as water deficit, drought periods and other extreme conditions and erosion processes. (www.gcrio. org/gwcc/booklet. html)
Global climate change, is affecting olive production efficiency as well as its product quality. The plant prefers areas with mild winters and short rainy seasons but is facing long and dry summers. It is resistant to drought but suffers much from harsh winters. Main problems are water requirements and irrigation management and frost resistance in some years. Irrigation during the pre-flowering— flowering period is essential to enhance reproductive performance and oil yields in areas with a dry winter-spring season. Also the adjusting agro technological, harvest and processing management aspects is main issues for the industry.
Climate change can have both positive and negative effects on olive crops. Lack of rainfall during the summer months will lead to irrigation deficit of olive plantations, decreasing of olive quality and reduced yields. The number of hail days will increase. Due to the change of temperature regime, the load of harmful pathogens will increase and consequently the need to use more integrated plant protection measures. The positive impact is manifested in the following :the sum of active temperatures will increase - it will be possible to focus on the cultivation of high quality olive varieties. Critical winter temperatures will be reduced - it will be possible to appear new regions of olive production (Tognetti at al., 2005).
East - South of Kakheti regions, temperatures are high and rainfall is low in the winter and early spring months. Current changes Climate (1986 -2015) in Kakheti caused the average temperature increased by 0.49-0.57 increased by 0.54 C. The increase in average air temperatures mainly occurs in June-October and in November-December there is a slight decrease in average temperature. Precipitation during the summer months was reduced by 20-25 mm. Annual precipitation is mostly reduced.
High temperatures have often been found to have detrimental effects on olive flowering in many olive cultivars and a better understanding of chilling requirements is needed. Lack of rainfall in the winter and spring also has resulted in an urgent need to evaluate water requirements from the flower differentiation period in the winter to early fruit bearing.
The map shows Climate change models (20412070) and (2071-2100) in Georgia (The National Environment Agency, 2020)
Predicted changes in climate according to the forecast models (2041-2070) and (2071 -2100) in Kakheti
Precipitation in 1986-2015; mm 27 35 50 88 123 99 G2 69 66 67 47 31 261 230 180 93 765
Telavi APr(1986-2015;1956-1985),nim 1 0 0 9 12 <24 ■16 <4 ■2 14 7 2 21 ■44 19 3 ■1
APr(1986-2015;1956-1985), % 4 0 0 11 11 ■20 ■21 ■5 ■3 26 18 7 9 ■16 12 3 -0.1
Precipitation in 1986-2015; mm 47 59 85 115 135 125 105 113 110 113 80 47 334 343 303 154 1134
Lagodekhi APr(1986-2015;1956-1985), mm 9 11 7 14 8 2 8 26 4 19 17 9 29 36 40 29 134
Kakheti APr(198fi-2015;1956-1985), % 24 23 9 14 6 2 8 30 4 20 27 24 10 12 15 23 13
Precipitation in 1986-2015; mm 27 38 57 95 104 87 56 52 60 82 49 32 256 196 191 97 741
Sagarejo APr(1986-2015;1956-1985), nim ■5 -3 5 ■21 ■25 ■16 ■10 20 6 4 ■7 ■62 16 ■4 ■57
APr(1986-2015;1956-1985), % ■16 ■7 ■10 6 ■5 ■19 ■31 ■24 ■14 32 14 14 ■3 ■24 9 ■4 ■7
Precipitation in 1986-2015; mm 29 31 46 66 95 75 50 39 55 57 40 21 208 163 153 81 604
Dedoplistskaro APr(1986-2015;1956-1985), mm 6 2 1 3 9 ■SO <4 <6 9 7 10 ■2 13 ■40 26 6 5
APr(1986-2015;1966-1985), % 26 7 2 5 10 ■29 ■7 ■13 20 14 33 ■9 7 ■20 20 8 1
The first forecast period (2041-2070) is proposed that the annual precipitation in Kakheti decreased by 8%. There is a significant increase in precipitation in winter (by 15%), a decrease in the remaining three seasons, the maximum decrease will be observed in spring (by 21%). The second forecast period (20712100), annual precipitation in Kakheti decreased by 19%. The reduction is especially significant in spring (28%) and autumn (16%). Growth only in summer (by 6%).
Major Measures of direction of Mitigation climate change on olive production are: Facilitate the arrangement of wells and irrigation systems to ensure drip irrigation in conditions of water shortage;
Support for the use of prediction, diagnosis and meteorological monitoring tools for harmful pathogens
Planting of windbreaks; strengthen insurance systems to reduce the negative effects of wind and hail used, also minor measuper - Improvement and adaptation of agro-technical measures - pruning, fertilization in lack of water. Study of mulching technologies -both organic and plastic mulch to maintain moisture in the soil; Application of conservative agricultural principles; Research on the use of specialized preparates
(caolin base) to prevent heat damage and facilitate their use.
Conclusions:
The following measures are important for the development of olive culture in Georgia:
1. Rapid response to droughts and other extreme events;
2. Irrigation management and introduction of innovative water use methods.
3. Search and finding of local varieties ("Tbi-lisuri", "Akhasheni", "Butko", etc.), which were distinguished by good adaptability and Resistance, recovery.
4. Create a nursery's, for propagation Georgian varieties and to be introduced in production.
5. Introducing new varieties and study of agronomical features.
References
1. Agro biodiversity of Georgia (Catalog) (2015). Tbilisi, pp. 10-32.
2. Borges, T. H. et al. (2017). Characterization of Arbequina virgin olive oils produced in different regions of Brazil and Spain: Physicochemical properties, oxidative stability and fatty acid profile. Food Chem. 215, 454-462.
3. Bradley, D., Griggs, W.H., (1961). Hartmann. Studies on self and cross pollination of olives under varying temperature conditions. Calif. Agric. 15 (3), 4-5.
4. Carr, M. K. V. (2013). The water relations and irrigation requirements of olive (Olea europaea L.): a review. 201. Exp. Agr, 49, 597-639.
5. Connor, D.J. (2005). Adaptation of olive (Olea europaea L.) to water-limited environments., Aust. J. 562 Agric. Res. 56, 1181-1189. doi: 0.1071/AR05169.
6. Chkhaidze G, (1998) Subtropical Crops. Tbilisi, pp.398-407.
7. Denney, J. O., and McEachern, G. R. (1983). An analysis of several climatic temperature variables dealing with olive reproduction. J. Amer. Soc. Hortic. Sci. 108, 578-581.
8. FAOSTAT (2019): http://faostat.fao.org/default.asp
9. Fruits of Georgia (catalog). (2001) F. Edited by Kvaliashvili. Tbilisi, pp. 34-44.
10. GEOSTAT (2019). Geostatic National Statistics Office of Georgia. www.geostat.ge.
11. Gucci, R., and Caruso, G. (2011). Environmental stresses and sustainable olive growing. Acta Hortic., 924, 19-30.
12. Gucci, R., and Fereres, E. (2012). "Fruit trees and vines. Olive," in Crop Yield Response to Water. FAO Irrigation and drainage paper 66 (Rome: Food and Agriculture Organization of the United Nations), 300-313.
13. Hartmann, H.T., and Panetsos, C. (1961). Effect of soil moisture deficiency during floral development on fruitfulness in the olive. P. Am. Soc. Horti. Sci, 78, 209-217.
14. Ketskhoveli N. (1957). Zones of Culti-vate3d plants in Georgia (in Russion). Tbilisi, pp.92120.
15. Lahrouni, M., El Abbassi, A. & El Messoussi, S. (2015). Olive tree growth dynamics under semi-arid conditions of AlHaouz region in Morocco. J. Mater Environ Sci 6, 2428-2436.
16. Lavee, S., Haskal, A., and Avidan, B. (2012). The effect of planting distances and tree shape on yield and harvest efficiency of cv. Manzanillo table olives. Sci. Hortic, 142, pp.166-173.
17. Lavee, S. (2014). Adaptation of commercial olive cultivation to new production zones and environments including in the Southern Hemisphere -possibilities, considerations and the problems involved. Acta Hortic, 1057, 27-40.
18. Maghlakelidze E. (2017). The importanceof the olive culture and thepotential for use in Georgia. Tbilisi, Source title Agro basis 8. pp.3 3-39.
19. Matesanz, S., Gianoli, E. & Valladares, F. (2010). Global change and the evolution of phenotypic plasticity in plants: Global change and plasticity. Ann. N. Y. Acad. Sci. 1206, 35-55.
20. Moriondo, M. et al. (2013). Olive trees as bio-indicators of climate evolution in the Mediterranean Basin. Glob. Ecol. Biogeogr, 22, pp.818-833.
21. Nicotra, A. B. et al. (2015). Adaptive plasticity and epigenetic variation in response to warming in an Alpine plant. Ecol. Evol. 5, 634-647.
22. OOC World Catalogue of Olive Varieties (2000). Madrid: International Olive Oil Council
23. Pierantozzi, P., Torres, M., Lavee, S., and Maestri, D. (2014). Vegetative and reproductive responses, oil yield and composition from olive trees (Olea europaea L.) under contrasting water availability during the dry winter-spring period in central Argentina. An. Appl. Biol, 164, pp.116-127.
24. Sanz-Cortés, F., Martínez-Calvo, J., Badenes, M. L., Bleiholder, H., Hack, H., Llacer, G., et al. (2002). Phenological growth stages of olive trees (Olea europaea). An. Appl. Biol, 140, pp.151-157.
25. Mailer, R.J., Ayton, J., Graham, K. (2010). The influence of growing region, cultivar and harvest timing on the diversity of Australian olive oil. J. Am. Oil Chem. Soc. 87: 877- 884.
26. Mousavi, S., Regni, L., Bocchini, M., Mar-iotti, R., Cultrera, N. G., Mancuso, S., Googlani, J., Chakerolhosseini, M.R., Guerrero, C., Albertini, E., Baldoni, L. (2019). Physiological, epigenetic and genetic regulation in some olive cultivars under salt stress. Sci. Rep. 9(1): p.1093.
27. Rapoport, H. F., Hammami, S. B. M., Martins, P., Pérez-Priego, O., and Orgaz, F. (2012). Influence of water deficits at different times during olive tree inflorescence and flower development. Environ. Exp. Bot, 77, 227-233.
28. Rapoport, H. F. (2014) The reproductive biology of the olive tree and its relationship to extreme environmental conditions. Acta Hortic, 1057, pp. 41-50.
29. Tognetti, R., D"Andria, R., Sacchi, R., Lavini, A., Morelli, G., and Alvino, A. Deficit (2007). irrigation affects seasonal changes in leaf physiology and oil quality of Olea europaea 713 (cultivars Franto-io and Leccino). Ann. Appl. Biol. 150, 169-186.
30. Torres M., Pierantozzi P., Searles P., Rous-seaux M.C., García-Inza G., Miserere A., Bodoira R., Contreras C., Maestri D. (2017). Olive Cultivation in the Southern Hemisphere: Flowering, Water Requirements and Oil Quality Responses to New Crop Environments. Front. Plant Sci, pp.27-32
31. Tognetti, R., D'Andria, R., Morelli, G., and Alvino, A. The effect of deficit irrigation on seasonal variations of plant water use in Olea europaea L.2005. Plant Soil 273, 139-155.
32. Tsulukidze O. (1953) Olive culture. Tbilisi.
33. Vavilov N. (1935). Theoretical basis of plant breeding. Volume I, (in Russian). Moscow, pp.26-79.
34. Zeleke, K., Mailer, R., Eberbach, P., and Wünsche, J. (2012). Oil content and fruit quality of nine olive (Olea europaea L.) varieties affected by irrigation and harvest times. New Zeal. J.Crop Hortic. Sci, 40, 241-252.
35. Zeleke, K. (2014). Water use and root zone water dynamics of drip-irrigated olive (Olea europaea L.) under different soil water regimes. New Zeal. Crop Hortic. Sci., 42, pp. 217-232.
36. Zhukovsky P. (1971). Cultivated plants and their relatives. (In Russian). Moscow, pp. 481-565.
