The origin of Herbaceous hybrid Group peony cultivars of the M. M. Gryshko National Botanical Garden of NAS of Ukraine collection and the prospects for their use

Purpose. To analyze the origin of the Herbaceous Hybrid Group peony cultivar collection of the M. M. Gryshko National Botanical Garden (NBG) National Academy of Sciences of Ukraine (NAS) and to determine the prospects for their use in breeeding work and decorative horticulture. Methods . The object of research was peonies of the Herbaceous Hybrid Gp of the NBG peony collection. The plants are grown on sunny open experimental and exposition plots of the NBG. Cultivars studies and phenological observations of plants were carried out during 2012–2022. Results. Varietal diversity of Herbaceous Hybrid Gp peonies of the NBG collection was analyzed by origin. The analysis showed that 122 varieties were created by US breeders, of which the Saunders breeding is represented by the largest number of varieties in the collection. 38 varieties are of Ukrainian breeding and created in the NBG. The analysis of hybrids obtained by distant crosses made it possible to identify combinations that give fertile offspring and to create promising double and triple hybrids. For decorative horticulture, 165 varieties of world and domestic breeding are recommended. They were grouped into four groups by flower color and two groups by the beginning of flowering. Plants of the early group start flowering before May 22 (± 4 days). The flowering of the late group of varieties occurs at the beginning of the flowering of the variety ‘Red Charm’ (May 22 ± 4 days) and later. Conclusions. For more than 50 years of introductory work with peony Herbaceous Hybrid Gp, 133 varieties of world breeding were tested at NBG. The main number of varieties was included in the collection in the first years of the 21st century. A comparative study of new varieties showed that most of them are sterile. Varieties ‘Dreamtime’, ‘Greenland’, ‘Quitzin’, ‘Lavender Whisper’, ‘Lemon Chiffon’, ‘Pastelegance’, ‘Pastelorama’, ‘Salmon Dream’, ‘Sunny Boy’, ‘Sunny Girl’, ‘Sunny Day’, ‘The Mackinac Grand’, ‘Vanilla Schnapps’, ‘Triphena Parkin’, ‘Pink Vanguard’, ‘Lavender Whisper’, were fertile and can be successfully used in the hybridization process. It was revealed that the source of early flowering of varieties created in the NBG was introduced wild species of herbaceous peonies: P. peregrina , P. wittmanniana , P. arietina . Peonies with double or semi-double flowers can be obtained by using P. officinalis ‘Rubra Plena’ with double flowers as a maternal component, and P. lactiflora varieties (‘President Taft’, ‘La Pionce’, ‘Lord Kitchener’, ‘Adolphe Roussean’, ‘M-lle Janne Riviere’) as paternal one also with terry flowers.


Introduction
The collection of peonies of the M. M. Gryshko National Botanical Garden (NBG) National Academy of Sciences is currently the largest in Ukraine and the richest in Eastern Europe. Having the status of a national treasure, the collection reflects a long period of historical development of the peony culture, which is a source of enormous genetic diversity and the Vasyl Gorobets http://orcid.org/0000-0001-6315-9033 Tetiana Shcherbakova http://orcid.org/0000-0003-1763-6841 basis of domestic breeding [1][2][3]. The mobilized varieties serve as the basis for morphological and biological studies of plants, study of the rhythms of their growth and development, and features of adaptation under conditions of introduction [4,5]. On the basis of the collected gene pool, methods of variety assessment and cultivation technologies are being developed. The collection is a standard for the State Variety Testing, a source of replenishment and expansion of the collections of regional botanical gardens and material for horticulture and greening. The collection also has scientific and educational value for breeders, amateurs, students of biological Variety studying and variety science and agricultural specialties, and schoolchildren [2,3].
Currently, the collection is a generic complex of Paeonia L., represented by three life forms and numbering 10 species, 650 varieties and 17 promising hybrid forms. It includes varieties of all garden peony groups: Lactiflora Gp (varieties based on a single species P. lactiflora Pall.), Herbaceous Hybrid Gp (varieties obtained by hybridization of herbaceous peonies of different species), Lutea Hybrid Gp (P. lutea Delavay ex Franch. (P. delavayi Franch.) and P. × suffruticosa Andrews varieties were used to create cultivars), Itoh Gp (obtained by crossing plants of different life forms), Suffruticosa Gp (based on P. × suffruticosa) [1,2].
The species have different ploidy; therefore, most of the Herbaceous Hybrid Gp varieties were obtained by distant hybridization are tetraploids or triploids [8][9][10]. Such varieties are characterized by a wide range of morphological features, which increases their decorativeness and adapts well to new cultivation conditions. They differ from other groups in early flowering periods, originality of the coloring (bright red, coral pink, yellow flowers in the color of flowers) and flower shape (simple, semi-double and double) [11,12].
The first attempts to create interspecific peony hybrids were made in Europe in the middle of the 19th century. French breeder V. Lemoine first crossed P. lactiflora with P. wittmanniana and obtained hybrids ('Avant Garde', 'Le Printemps', 'Mai Fleuri', 'Russi Major') with an early flowering period. The German breeder G. Arends, crossing P. peregrina with P. wittmanniana, obtained hybrid forms with light yellow and pink flowers.
Three of his varieties are registered in the Peony Registry of the American Peony Society: 'Alpha', 'Mai Königin', 'Reine de Mai' [13]. In England, P. Barr was engaged in peony interspecific hybridization. Having done a lot of work on crossing P. officinalis and P. arietina and their breeding forms, he received a number of seedlings, among which he selected the variety 'Northern Glory'.
At the end of the XIX -beginning of the XX century American breeders A. Saunders, L. Glass cock, E. Auten crossed P. lactiflora and P. officinalis and obtained about a hundred interspecific hybrids. Also, from crossing P. officinalis and P. tenuifolia, L. Glascock obtained hybrid forms, one of which was registered as 'Laddie' variety. Professor A. Sanders made a particularly great contribution to the creation of new varieties. His work made it possible to extend the flowering period of peonies by two to three weeks compared with varieties based on P. officinalis, P. tenuifolia and interspecific hybrids obtained by W. Lemoine. He created new peony varieties with flowers of scarlet, red, light cherry, pale lilac, waxy hue with an interesting border of petals, as well as the color of bone and opal. But the greatest achievement was to obtain a pink color with orange-pink, coral, cherry shades, which were previously present only in Chinese bush peonies and never seen in herbaceous varieties [1,13].
In Ukraine, varieties of the described peony group began to appear after the Second World War and are cultivated in the collections of botanical gardens, arboretums and amateur flower growers. Peony collection of the NBG is the most represented in terms of assortment.
The purpose of the research is to analyze the origin of the Herbaceous Hybrid Group peony varieties from the collection of the M. M. Gryshko National Botanical Garden of NAS of Ukraine (NBG) and to determine the prospects for their use in breeding work and ornamental horticulture.

Materials and methods
Plants of peony varieties of the Herbaceous Hybrid Gp of the NBG peony collection were the object of research. Varieties of the Herbaceous Hybrid Gp were included to the collection by exchange and purchase of planting material (parts of rhizomes with three or four rudimentary shoots) with botanical institutions, amateur flower growers and garden centers in Ukraine and the world. The introduction forecast was carried out using the methods proposed by P. E. Bulakh [14], taking into account the varietal characteristics of the plants.
All available variety descriptions and variety descriptions from the Peony Registry of the American Peony Society were used for variety identification [13]. Plants of the peony collection are grown in the open sunny experimental and exposition areas of the NBG. The sites are located on the Pechersk slopes of the Kyiv Upland in the natural landmark "Zvirynets" (50°32′ N and 30°33′ E) in the southeastern part of Kyiv on the border of two physical and geographical zones: the forest zone of Polissia and Forest-Steppe zones. The climate is temperate continental. The average annual air temperature is 9.5 °C [15].
A comparative study of peonies of foreign breeding and varieties created in the NBG was carried out according to the method of V. M. Bylov [16] and the Method for conducting an examination of peony varieties (Paeonia L.) for Distinctness, Uniformity and Stability [17]. According to these methods, 6 plants of each variet y were used for research [16,17]. During 2012-2022 phenological observations of plants were carried out, the results were statistically processed [16,18]. The most important indicators of the decorative variety value were singled out: the color of the flower and the beginning of flowering, according to which the varieties were grouped. Grouping varieties according to these parameters allows us to show the diversity of the peony assortment, which can be used in the selection of varieties for ornamental horticulture and breeding.
Although the weather conditions significantly shift the dates of the beginning of the variety flowering, however, the correlation between varieties regarding the timing of flowering is maintained: that is, the earlyflowering variety always blooms earlier than the middle one, the middle one before the late one. Therefore, based on the determined timing of the beginning of each variety flowering, all varieties were divided into two groups relative to the beginning of flowe ring of the medium-flowering variety 'Red Charm': group I -varieties blooming before the flowering of 'Red Charm', group II -after the beginning of its flowering [19]. Such a distribution of varieties into groups allows us to select varieties to expand the range of decorative flower arrangements. This distribution of varieties by groups makes it possible to choose varieties for expanding the range of flower arrangement decorativeness.

Results and discussion
Peony introduction and breeding started at the beginning of the NBG construction and development. The formation of the collection fund began in 1947, when 30 first varieties were obtained through the German company "Lange". Later the collection was replenished with samples from other botanical gardens, experimental stations, scientific institutions and our own breeding.
The first varieties of the Herbaceous Hybrids group were included in the collection in 1971-1976 ( During the 80-90s of XX century 26 more varieties were introduced. The main number of varieties was included in the collection in the first years of the 21st century, which was due to the import of new varieties of world breeding to Ukraine and the need to test them in our conditions. In particular, during 2000-2019 the collection fund was enriched by 76 new varieties.
In total, over 50 years of introduction work with peony Herbaceous Hybrid Gp, 133 varieties of world breeding were tested in the NBG.
The analysis of the origin of the introduced varieties showed that 121 varieties were created by US breeders (Fig. 2). Of them, the collection of A. Saunders (33 varieties), E. Auten (13 varieties), L. Glasscock (10), and U. Bockstoce (7 varieties). The collection also includes varieties created and registered in Canada, Belgium, Sweden, Russia, the Netherlands, and France.
Plants. The priority direction of breeding work was the creation of varieties with early and very early flowering periods. Wild-growing species of herbaceous peonies were introduced into the NBG as a source of early flowering: P. peregrina, P. wittmanniana, P. arietina. The carriers of high decorativeness of the flower and high productivity of flowering were the varieties P. lactiflora and P. officinalis and their decorative subspecies and forms.
In the process of analyzing the results of our own breeding work, great form-building possibilities of distant hybridization were revealed, consisting not only in a combination of useful features of the original forms, but also in the appearance of many new ones that are not characteristic of the parental generation. Since in all combinations of crosses where wild-growing species were parental forms, the first generation was dominated by a negative trait -a single flower form, therefore the backcross method, recurrent backcrossing, and crossing of terry P. lactiflora varieties with fertile interspecific hybrids F 1 were applied.
The results of hybridization showed that the most decorative forms of peonies with double or semi-double flowers can be obtained using P. officinalis 'Rubra Plena' with double flowers as the maternal component, and P. lactiflora ('President Taft', 'La Pionce') as the paternal component, 'Lord Kitchener', 'Adolp he Roussean', 'M-lle Janne Riviere') also with double flowers (Table 1). For example, variety 'Yuvilei Kyieva' was created by crossing P. officinalis 'Rubra Plena' with P. lactiflora 'Adolphe Roussean', 'Benefis' variety -by crossing P. officinalis 'Rubra Plena' and P. lactiflora 'President Taft'. Sometimes it was possible to obtain double forms by crossing P. officinalis 'Rubra Plena' with varieties or breeding numbers of P. lactiflora that have single flowers. This is how the variety 'Chaklunka' was obtained.
Most P. lactiflora cultivars were crossed with F 1 distant hybrids (♀ P. officinalis 'Rubra Plena' × ♂ P. peregrina) and triple distant hybrids were obtained. The varieties of Auten, Glasscock and Bockstoce present in the collection owe their origin to P. lactiflora and P. officinalis.
It should be noted that the French cultivar 'Smoutii' (Smout / van Houtte, 1843) is the oldest one in the collection. The presence of P. tenu ifolia genes in its genotype allows the variety to bloom already in the first decade of May.
From the data shown in Figures 1 and 2  Continue Table 1 One of the most important decorative features of a peony flower, which is primarily taken into account by gardeners and landscape designers, is its color. We combined all the variety of peony colors and shades into four groups: red (light, dark red flowers, orange-red, purple-red, cherry, etc.), pink (light, dark pink flowers, salmon-pink, coral, coral pink, lilac pink, purplish pink), white (white, creamy white), yellow (light yellow petals, bright yellow, lemon yellow, creamy yellow) ( Table 2).
The analysis of the variety origin have showed that those of early breeding in 20s-60s of the XX century mainly have a red flower color, inherited from P. officinalis, P. tenuifolia, and P. peregrina.
Varieties of light pink, pink, coral-pink color were obtained mainly in the second half of the 20th century, when various forms of P. officinalis, P. arietina and subspecies P. daurica and P. anomala were actively included into the breeding process.
At the end of the 20th and the beginning of the 21st centuries, a group of new varieties with bright yellow flower color appeared. The coloring was caused by genes that induce the synthesis of kaempferol glycosides of yellow color, obtained from the ancestral P. daurica subsp. mlokosewitschii [20]. New cultivars have been the result of a complex hybridization of early yellow-flowered cultivars: 'Moon-rise', 'Nova', 'Rushlight', 'Ballerina', 'Elizabeth Cahn', 'Claire de Lune', 'Prairie Moon'.
Tests of new varieties in the conditions of Ukraine showed that the most promising of them were: 'Lemon Chiffon' -D. Reath's variety with a double shape and lemon-yellow color of the flower, yellow and cream-yellow K. Laning varieties 'Sunny Boy' and 'Sunny Girl' (Fig. 3). Introduced in the NBG, the Swedish variety 'Quitzin' (author Prof. Harald Fawkner) has large bomb-shaped double flowers with creamy peach petals and bright yellow staminoids. It is characteristic that on one plant there are flowers, both single and of varying degrees of doubling. 'Quitzin' turned out to be quite promising for further breeding, resulting in its creamy pink veriety 'Trip hena Parkin' of 2009.
Obtaining varieties with cream-pink, pinkcream, pastel color of the flower has become one of the modern trends in the breeding of this peony group. Among them, Pastelegance (Seidl, 1989) and Pastelorama (Seidl / Bremer, 2013) turned out to be promising in our conditions. Both are the result of crossing pink and yellow Salmon Dream ('Paula Fay' × 'Moonrise') parental forms with 'Lemon Chiffon' and R. Anderson's hybrid, respectively.
In the NBG, P. daurica subs. wittmanniana, is included in the breeding work, which made it possible to obtain a light pink-cream variety 'Vesniane Defile'.

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Comparative study of modern varieties showed that most of them are sterile and do not bear fruit. The sterility of varieties, which in most cases are triploids, is mani- The beginning of the peony flowering, as well as other ornamental plants, is one of the most significant indicators that allows choosing the right varieties for both cut and landscape compositions. The timing of the begin- ning of flowering is a varietal characteristic, which strongly depends on the natural and climatic conditions of the region of introduction. However, the correlation between varie-ties regarding the timing of flowering is maintained. We divided the introduced Herbaceous Hybrid Gp cultivars into two groups relatively to the beginning of flowering of the 'Red Charm' cultivar, which begins flowering on 22.05 ± 4 days under NBG conditions. Under the conditions of the NBG, the varieties of the first group bloom in the last days of April and until May 22. Varieties of the second group begin flowering on May 23 -the first days of June (Table 2). Varieties whose parent forms were early flowering species and their forms begin flowering earlier. Thus, 'Earlybird', one of the first varieties of Saunders, which blooms in the conditions of the NBG as early as April 28 ± 3 days, was created on the basis of the hybridization of P. woodwardi and P. tenuifolia. Another early (May 5 ± 4 days) Saunders variety 'Seraphim' was obtained by crossing P. lactiflora and P. macrophylla. 'Starlight' -a hybrid of P. lactiflora, P. officinalis, P. macrophylla, P. daurica subsp. mlokosewitschii blooms on May 12 ± 3 days.
An early flowering period is also noted for variety 'Orlyonok' (V. F. Fomicheva), which blooms on May 12 ± 4 days due to the presence of P. tenuifolia genes in its genotype. On May 11 'Tiny Tim' (Smirnov, 1975) begins its flowering, which is due to the early flowering of P. tenuifolia 'Rubra Plena'. Early flowering 'Novost Altaya' variety (Z. I. Luchnik) is due to the crossing of P. lactiflora with P. anomala.
Among the introduced cultivars, Autena cultivars are among the first to bloom: 'Early Scout' (15.05 ± 5 days) was created on the basis of P. lactiflora 'Richard Carvel' and P. tenuifolia; 'Favorita' (16.05 ± 4 days) is the result of hybridization between P. lactiflora and P. officinalis.

Conclusions
For more than 50 years of introduction work with Herbaceous Hybrid Gp peonies, 133 varieties of world breeding were tested in the NBG. The main number of varieties was included in the collection in the first years of the 21st century, which was due to the introduction of new varieties of world breeding to Ukraine and the need to test them in our conditions.
Varieties created in the late XX -early XXI century with bright yellow, pastel, pinkcream, cream-pink flower color, proved to be promising for cultivation in Ukraine. Comparative study of new varieties showed that most of them are sterile. For ornamental horticulture, 165 varieties of world and domestic breeding, combined into four groups according to flower color and two groups according to the beginning of flowering are recommended, which makes it possible to select varieties to expand the range of decorative flower compositions.