Pawpaw (Asimina triloba (L) Dunal) bioecological peculiarities under the conditions of the Ukraine’s steppe
UDC
581.95:634.41(477)
The authors present the data conerning the successful introduction of the minor crop pawpaw (Asimina triloba (L) Dunal) in the Kherson region and discuss in detail the results of the multi - year phenological observations. The plants of the resear ched crop have appeared to pass a full vegetation cycle for 183-185 days in the experiment conditions and gives a full-bodiet crop. The abiotic factors effect (low temperatures, drought) has been studied as well. Thе pawpaw adaptation to the growing conditions has turned out higher than that of peach and apricot and close to apple. On the basis of the investigations results and their discussion this crop has been recommended for the extensive introduction in the Ukraine’s Steppe zone.
Key words: pawpaw, introduction, phenology, frost-and drought-resistance, fruits, composition.
Pawpaw (Asimina triloba (L) Dunal) bioecological peculiarities under the conditions of the Ukraine’s steppe
O. A. GRABOVETSKA, Cand Biol SciKirovograd State Agricultural Research Station, NAAS, 2 Central str., 27602, Sozonіvka, Kіrovograd district, Kіrovograd region, e-mail: ograbovetska@mail.ru
V. M. EZHOV, Academician of NAAS of Ukraine
Institute of Horticulture, NAAS of Ukraine, 23, Sadova str., Kyiv-27, 03027, e-mail: ezhow.valeriy@gmail.com
The data on the successful introduction of less common papaw (Asimina triloba (L) Dunal) in the soil and climatic conditions of the Kherson region of Ukraine are cited. Discussed in detail the results of long-term phenological observations; is shown, that under experimental conditions culture papaw comes full cycle vegetation for 183-185 days and gives a full harvest. Also studied the effect of low temperature and drought on the culture; is shown a higher adaptability to abiotic factors in comparision with the peach and apricot close to the apple-tree. On the basis of research and discussion culture papaw recommended to wide spread in the steppe zone of Ukraine.
Asimina triloba (L.) Dunal, azymina, pawpaw – a relatively new, yet in Ukraine of rare species that country and in particular in the steppe almost not studied. Genus Asimina L. belongs to one of the largest tropical families – Annonaceae DC, which includes 130 genera and over 2100 species, some common even in the subtropical zone. The greatest number of species growing in the Old World [22, 24]. In USAazymina area located in southern Ontario, Iowa, then to east Texas and Nebraska to northern Florida. In culture azymina reached the southern regions of Canada, for which typical winter lows to -25...-30 ᵒC [23,24]. Azymina – small deciduous tree 5-10m tall, rarely to 15m, crown shape ovate, pyramidal or rounded with a thick sympodial thin branches that may classical palmettes. The plant has thin stems with large wedge-shaped leaves, beautiful dark chestnut-colored flowers with a mild pleasant aroma [3,4,7,10,12]. The fruit is fragrant, juicy and sweet, with a carbohydrate content of 16 to 25% [8], ascorbic acid - up to 50mh-%, dry materials - to 29%, which is higher than many fruit crops. In contrast, fruits of azymina have very low acidity- from 0.16% to 0.5%, a relatively high content of pectin - 0.16-0.2% [11]. The content of potassium (314-368 mg / 100g) azymina similar to apricot, while magnesium, iron, copper, zinc, manganese and phosphorous containing more than apples, bananas and citrus fruits [18]. More in azyminafruits protein, and levels of essential amino acids from 29.3 to 47.2%. Consume them fresh when they become soft creamy consistency, also used to make jams, jellies, yogurt, candied fruit, ice cream, etc. [11,20]. According to the literature, valuable properties are not only fruit, but other parts of the plant, including the leaves, which found 5.7% hydroxycinnamic acids, 6-8% and 0.1-0.3% flavanoyidiv volatile compounds mainly terpenoyid`s nature [5.6].
Introduction of azymina in culture in the United States began only in the early 20th century to the Second World War was used for 22 varieties and 60 years ago - 56 [22]. .Introduction ofazyminya in Europe took place in 1736, and to the Ukraine, exactly to Nikita botanical garden, she came in 1819, again in 1922, [18]. Today azymina can be found in amateur gardens of Kyiv, Dnipropetrovsk, southern and western regions of Ukraine; oldest representative of its growing in the Botanical Garden of Odessa National University since 1948: a tree 12m tall with a trunk diameter of 35 cm.
More systematic works by azymina introduction to the culture began with the Nikita Botanical Gardens within 90 years of the last century; In 2004, 14 varieties of breeding the United States was transferred from there to the state research enterprise "Novokakhovska", belongs today toKirovohrad State Agricultural Experimental Station NAAS. These varieties - Sweet Alisa, Wilson, Mango, Overlees, Davis, Rebeca Gold, Taylor, Taytwo, Wills, Sunflower, Pensilvania Gold, NC-1, Mitchel, Prolific, along with 25 previously obtained forms create the biggest in Ukraine collection of azymina.In these long-term studies on the introduction azymina in the steppe zone of Ukraine Generally accepted methods used to assess the drought resistance of plants [14], climate overwintering and frost culture [15, 17], meteorological observations [1, 21]. Evaluation of soil conditions growing culture was carried out in [19]. The paper also used conventional methods for biochemical studies [7]. In addition, analysis of inorganic elements was performed by atomic adsorption spectrophotometry, and fatty acids - using gas-liquid chromatography of ethyl esters of fatty acids after corresponding hydrolysis and esterification of them [2].
State research enterprise "Novokakhovska" located within Kakhovka–Low Dnepr sand arena. On the territory of experimental enterprise there are three types of soil: chornozem (black earth) loamy, sandy prairie sod and turf-steppe sand-connected. Experimental collection area of azymyna located on soils with humus layer of 76 cm, humus content in the topsoil 1.33% and sod-steppe sandy soils with humus layer of 87 cm and humus content in the topsoil 0.99% [19].The climatic conditions that occurred experimental studies are classified as moderately continental. The average July temperature is 20-24 ᵒC, January - 2-9 ᵒC below zero, the average temperature 9.3-9.5 ᵒC. The amounts of temperatures above 10 ᵒC are 1650-2030 ᵒC, rainfall during the summer period 130-240 mm, annual precipitation 360-460 mm. The average duration of the period without frost is 200-207 days, growing period 200-215 days. Droughts of varying intensity occur annually [1] .Summary, soil and climatic conditions can be assessed as satisfactory for the cultivation of fruit crops, especially if irrigation.
Our long-term study showed that the climate of the steppe zone of Ukraine or the north of Kherson provided proper farming rhythms correspond to the growth and development of culture azymina. In particular it was investigated periods beginning, duration and complete walkthrough main phenological phases that make up the annual cycle of plants: opening of generative and vegetative buds, flowering, growth of shoots , ripening fruits, falling leaves period.
It was established that the beginning of vegetation - sap flow in plants begins at steady transition of average temperatures over +5 ᵒC and took place on the first week of April; opening of generative and vegetative buds occur at the end of the second and third week of April, when the sum of active temperatures is 109.6-231.5 ᵒC. The duration of flowering depends on the weather conditions, especially the soil moisture and air in this period; due to lack of moisture, it is much reduced. Growth of shoots begins during flowering azymina by sum of effective temperatures 271.5- 333.2 ᵒC, maximum intensity occurs at the end of May and the first two decades of June, but in general it is completed in mid-July, and the young trees continued to early August. Bookmark generative buds occurs in growth this year, and their formation is completed with the end of shoot growth.Significant role in forming the crop conditions azymina play pollination and biological characteristics of varieties. Pollination in turn depends on the selection of varieties, but also on weather conditions and availability of insect pollinators. Under the conditions of Steppe of Ukraine pollination of fruit crops carry insects - flies Wohlfahrtia magnifica (family Sarcophagidae), Calliphora vomitoria (family Calliphoridae), Bibio hortulans (family Biblionidae), wasps Cerceris Latr (family Sphecidae) and others. Cross-pollination is ensured when selecting genetically diverse varieties. Under this condition, ripening fruit azymina begins at the end of the third decade of August or beginning of the first decade of September, when the sum of effective temperatures above 5 ᵒC is 2440-2550 ᵒC. Thus, the temperature of this amount is sufficient for a complete walkthrough of biological processes during development and maturation of seeds in the fruit. Interestingly, in Western Caucasus complete cycle of vegetation azymina occurred in 210-214 days by the sum of effective temperatures of at least 2400 ᵒC [11]. According to our data, the average length of the growing season researched forms and varieties azymina in terms of Steppe Ukraine is 183-185 days, with complete vegetation occurs in late October or early November. In mid-October azymina leaves become yellow color, then starting in the third decade of October, or according to the first frost in early November fall.
For Steppe Ukraine usual mostly mild winters with frequent thaws and long and unstable snow cover changing a sudden sharp decrease in temperature during the invasion of cold Arctic air mass. Temperature drops in winter when the plants are in a state of forced rest, very dangerous. Thus the period of entry of plants into a state of deep rest and forced its duration depends on a very important factor in the introduction as hardiness.
In our studies, hardiness of azymina evaluated the results of years of visual observations, test methods according to varieties for distribution in Ukraine [16]. By this method, the highest score 9 corresponds absent or very low freezing, low to yellowish color darkening wood, small superficial burns bark on the trunk and branches of the skeleton; possible shrinkage over the one-year increments, isolated small branches and freezing parts fruitful branches.
Established that the studied varieties and forms azymina in terms Steppe Ukraine meet this ball, that is winter-hardy. During the years 2006-2013 the absolute minimum temperature was 17.4 ᵒC below zero, with an average 12.7ᵒC below zero. During this period, any damage to trees and generative buds frost was observed, fine mature trees bloomed and fruited. At the same time, annual seedlings observed freezing tips and even loss of individual plants, while in the two-year and three-year plants the negative impact of low temperatures was not observed, which suggests that the increase hardiness of azymina with age.
Over the past 50 years, the most extreme conditions differed winter of 2005-2006. If the average temperature for the week of December and the first two decades of January was close to the norm, then it was much lower than the norm: in the third decade of January 13.1ᵒC, and in the first and second decade of February according 6.3 and 5.5 ᵒC below zero. This absolutely minimum temperature reached 26.7ᵒC below zero. Due to extreme temperature drops laid in summer 2005 on adult trees generative buds died and falled. Spring bloom a flower from buds formed later that were less developed and better preserved; regrowth occurred from apical buds. On mature trees aged 10-12 years experienced a shrinkage of small overgrown branches, inside the shadow of crown, but damage to wood as many years and one year, did not exist. During the growing season the leaves well developed, almost normal size and color. Because of this wintering, the delay before flowering, decreased its intensity; weight of the resulting yield dropped to 30% of the average. Thus, extreme winter conditions 2005-2006 years negative impact on only one of the next cycle of vegetation.
Along with frost, an important indicator of prospects spread culture of plants in a particular region is drought, which characterizes the ability of plants to withstand prolonged drought and related dehydration without significant irreversible disorders of vital functions.
Long-term visual observations have shown that if the wheels mulching and watering in summer drought studied varieties and forms azymina accordance with the accepted methods is estimated at 5-7 points, ie among varieties and forms is a medium drought (slight increase, possibly yellowing leaves, moderate head falling by leaves and fruits) and drought (normal growth and leaf color, a slight falling by leavs and fruit).
Visual observations were supplemented by analytical studies. Experimentally, in the dry period, the Ukraine steppe relative leaves turgor resistance of azymina is 74.9-92.9%, and water shortage equal to 6.1-9.9%. Based on the above it can be concluded that drought conditions of azymina in Steppe Ukraine less than similar both in natural habitats and in the subtropical region of [8, 9], provided irrigation culture is quite promising.
Features extensive introduction of every obscure vegetable crops depend not only on the characteristics of the vegetation and its adaptive properties, but also on the biochemical composition of the final product, in this case the fruit. Detailed analysis of the composition and content of biologically active substances in fruits azymina, led to the conclusion of a significant nutritional and biological value (see table).
The content of some biologically active substances in fruits azymina
|
Component |
Content, g/100g |
Component |
Content, mg/100 g |
|
Mono-, disaccharides |
16.8-22.4 |
Minerals |
604-726 |
|
Pectin |
1.88-2.02 |
Potassium |
314-368 |
|
Organic acids |
0.3 -1.0 |
Magnesium |
109-120 |
|
Protein |
0.8 -1.4 |
Vitamins |
86.2-89.1 |
|
Vegetable oil |
0.6-1.4 |
Phenolic substances |
183-188 |
As part of biologically active substances especially noticeable high content of monosaccharides and disaccharides, including 42-65% of the total accounted for sucrose, glucose 10-18% and 8-15% fructose. A third water-soluble pectin fraction is represented, the rest - protopectin. In the composition of organic acids malic and citric prevail, and the protein contains 27.1 - 34.5% of the total essential amino acids. Vegetable oil of azymina consists mainly of oleic, linoleic and palmitic acids and unsaturation index of oil is 87-88%, which assigns it to semi-drying vegetable oils. Among vitamins rather high content of vitamin A, 65mh-%, and C (20.9mh-%). The content of magnesium in 100 g of fruits up to 25% and potassium 15% of the daily needs of the human body. Phenolic substances of azyminafruits represented almost half leycoanthocyanes, the rest is dominated by catechins and flavanols. Analysis of azymina leaves revealed that they contain 14-15 mg / 100 g of vitamin C and 460-540 mg / 100 g of phenolic compounds [18].
Summarizing submissions, we can conclude that climate by Steppe Ukraine meet seasonal rhythms of growth and development azymina that allows this culture annually complete a full cycle of vegetation.
In terms of hardiness culture of azymina far outstrips traditional fruits such as peach and apricot, approaching this indicator to apple and plum. As for drought, culture azymina conditions for farming irrigation and proper enough perspective to the steppe zone. In general, the number of adaptive azymina averages 80-90 points, on a scale that estimates introduction describes this culture as promising for growing conditions in southern steppes of Ukraine. An additional argument in favor of this conclusion serve the composition of biologically active substances azyminy, among which are carbohydrates, minerals and vitamins.
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