Analysis of the composition of Iris × hybrida hort. collection of Nikitsky Botanical Gardens-National Scientific Center by valuable decorative and economic-biological features

The article presents the results of the analysis of the cultivar composition of the Iris × hybrida hort. collection of Nikitsky Botanical Gardens according to bloom season and color classification. As a result of the analysis of phenological observations, the average long-term dates of the «beginning of flowering» phase in the conditions of the South Coast of Crimea were determined for all collection cultivars. The definition of the studied cultivars according to the bloom season within the garden groups into early flowering, medium flowering and late flowering has been carried out. Lists of cultivars by color classes are presented. The data obtained can be used in the practice of landscaping resort areas to create long blooming without a break compositions with the inclusion of Iris × hybrida hort. cultivars from various garden groups. The definition of Iris × hybrida hort. cultivars of NBS – NSC collection by color classes in accordance with the classification proposed by The American Iris Society was also carried out. Lists of cultivars by color classes are presented. The data obtained can be used by landscape architects to create flower arrangements in specific color spectrum in combination with companion plants.


Introduction
One of the main areas of work of botanical gardens is the preservation of biological diversity. For this purpose, in the Nikitsky Botanical Gardens -National Scientific Center (NBS -NSC), collections of ornamental flowering crops have been created, maintained and increased, on the basis of which introduction and breeding studies are conducted [1][2][3]. One of such collections is the collection of bearded garden iris (Iris × hybrida hort.) [4]. In world practice, in recent decades, this culture is one of the most popular and demanded, which is confirmed by numerous studies carried out in different botanical gardens [5][6][7][8].
Variety of Iris × hybrida hort. cultivars from different garden groups allows them to be widely used in various types of flower decoration: from planting on rocky hills to creating large groups on the lawn and mixborders, as well as for cutting [9,10]. However, there is a shift in blooming season of Iris × hybrida hort. in different climatic zones, and a decrease of flower color steadiness to fading, which is expressed in a rapid loss of the color intensity of the flower. The southern coast of Crimea is a zone of dry subtropics of the Mediterranean type. In subtropical conditions, the year is divided not into four seasons, but into two periods: cold and warm. April is taken as the beginning of the warm period, the average monthly temperature of which is close to 10° C [11]. Due to these factors, many ornamental flowering crops in the South Coast enter the blooming phase much earlier than in other, more northern regions of Russia.
The date of the beginning of Iris × hybrida hort.collection formation in the NBS -NSC can be considered the 70s of the last century, when in 1976 Nikolai Antonovich Shelygin first carried out research on garden iris cultivars in the South Coast of Crimea. At the same time, the first results were summed up, as a result of the analysis, it was concluded that the introduction into culture and the use of Iris × hybrida hort. in the landscaping of the South Coast of Crimea was prospective [12]. Subsequently, the collection of Iris × hybrida hort. of the Nikitsky Botanical Gardens was in different conditions. Regular stocking of collection funds with new domestic and foreign selection cultivars, possessing various biological and morphological features, was began by Alexander Stanislavovich Krasovsky in the mid-80s and continued by us since 2001. Currently, the collection of Iris × hybrida hort. in the NBS -NSC includes 300 domestic and foreign cultivars of different years of creation, from different garden groups.
The purpose of this study is to analyze the composition of Iris × hybrida hort. cultivars of NBS -NSC collection by such features as blooming season in conditions of Southern Coast of Crimea and color class affiliation.

Materials and methods
The objects of the study were 300 Iris × hybrida hort. cultivars from the collection of the NBS -NSC. Study of Iris × hybrida hort cultivar's features was carried out according to generally accepted methods [13,14]. Rhythms of growth and development were studied according to the "Methodology for conducting phenological observations in the botanical gardens of the USSR" [15]. The definition of cultivars by flower color classes is given according to the classification adopted by the largest and most authoritative community of garden iris growers in the world, The American Iris Society (AIS) [16].

Results and discussion
Iris × hybrida hort. collection of the Nikitsky Botanical Gardens includes 300 cultivars from the main garden groups. The main parameter for various garden classifications in the world is the height of the generative shoot, as well as for some groups such parameters as the size of the flower and the blooming season are additionally taken into account. All Iris × hybrida hort. cultivars of the NBS -NSC collections are proportioned as follows: 253 cultivars belong to the group of tall bearded irises, 10 cultivars -to the group of medium and 37 -to the group of dwarf ones. Thus, the group of tall cultivars is represented most fully in the collection. An important feature for ornamental plants is the season and duration of blooming. Blooming sequence of Iris × hybrida hort. garden groups is strictly defined, the first to enter the blooming phase are the dwarf cultivars, then the cultivars of the medium group and the cultivars of the tall group complete this process. It should also be noted that within each garden group there are cultivars with different blooming season: early blooming, middle blooming and late blooming.
As a result of the analysis of long-term phenological observations (from 3 to ten years or more, depending on the year when cultivar was introduced into collection), it was determined that the average long-term dates of the bloom beginning of dwarf cultivars on the South Coast of Crimea fall on the second decade of April. Early-bloom cultivars of dwarf irises enter the blooming season from 11 to 14 April. The total blooming duration of collection tall cultivars is 45 days. Thus, the total blooming duration of collection bearded iris cultivars from all three garden groups on the South Coast is about 60 days (Fig. 1), what is of particular interest for use of Iris × hybrida hort. cultivars for landscaping in the resort area of Crimea. plants, based on reference to a color group, for example: white, yellow, blue, etc., do not provide a complete understanding and do not reflect the actual color of the certain iris cultivar. In this case, the most practical and informative is the classification developed by the AIS and built on the principle of a «template» of flower color and on the widespread types of color patterns among irises, which allows you to reflect most fully the color features of a particular cultivar, depending on belonging to a certain type of color class: -self -the inner (standards) and outer (falls) perianth lobes are colored in the same color; -bitone or neglecta -standards and falls are colored in tones of the same color, different in intensity; -reverse bitone -standards and falls of a different tone of the same color, standards are darker than falls; -bicolor -the upper and lower lobes are colored differently. Additionally, two-color cultivars are subdivided into the such types as: -variegate -standards for yellow shades, and falls are colored in the range from brownish to purple; -amoena -standards are white or almost white, falls are colored; -reverse amoena -ccolored standards, white falls; -«Emma Cook» -only a bordure along the edge of the outer perianth lobes is colored; -«Debby Rairdon» -standards light coloured, falls are white with a wide border of the standard color along the edge of the petal; -plicata -a type of coloring with a pattern of dots and strokes of dark colors on a light base undertone, the pattern often fuses into a wide band; -luminata -basic, lighter tone, appears on the standards and along the edge of the outer lobes in the form of the thinnest rim; -glaciata -a type of coloration similar to plicata, but without dark pigments; -blend -iridescent color of a flower, combined of two or more colors; -broken color -"splattered" color, chaotic strokes, strokes of one or more colors. The studied iris cultivars of the NBS -NSC collection are distributed as follows ( Thus, the analysis of collection cultivars of Iris × hybrida hort. according to the color classes showed that all currently defined types of color patterns are represented in the collection of the NBS -NSC, it should also be noted that their quantitative ratio is presented in proportion to the modern world assortment.

Conclusions
As a result of the studies, the average long-term dates of the blooming beginning of Iris × hybrida hort. cultivars of the NBS -NSC collection in the conditions of South Coast of Crimea were determined. All collection cultivars are relatively defined by blooming season into: early-bloom, middle-bloom and late-bloom, within their garden groups. The total blooming duration of the studied Iris × hybrida hort. cultivars of the NBS -NSC collection was determined, which is about 60 days. Also, all collection cultivars are classified by flower color types in accordance with the classification proposed by The American Iris Society (AIS). It was found that in the collection Iris × hybrida hort. of Nikitsky Botanical Gardens all types of flower color classes from the AIS classification are presented. The data obtained can be used by various specialists in the design of landscaping plantings using Iris × hybrida hort. cultivars from different garden groups to create long blooming without a break compositions with the widest range of colors and the possibility to create a huge number of unique color spectrums in combination with companion plants.