Growing a low-growth clone planting material of cherry from green cuttings

. We dealt with the study of the ability of different varieties of cherries, cherries and vegetatively propagated rootstocks to reproduce by green cutting explants in artificial substrates in buildings with a controlled microclimate inside. As varieties in the experiment, such varieties of cherries as Shpanka black, Podbelskaya, Shubinka and Lyubskaya, cherries Revershon, Bakhor, and Drogana yellow were used. Of the vegetatively propagated rootstocks, the following were studied: P-1, P-2, P-3, PN, VTS-13, VP-1, ORP-2, ORP-3, VSL-2 (Krymsky 5), SAV-6R. Of the used cherry varieties, the best rooting of green cuttings was possessed by such cherry varieties as Shpanka black, Podbelskaya and Shubinka, with a quality index of cuttings rooting in the substrate of 70.1 to 83.5%. In sweet cherry varieties, this indicator was 2.5 times lower and generally did not exceed 30.2%. Vegetatively propagated rootstocks provided high quality results of rooting of cuttings explants. In almost all of these rootstocks, the rooting rate of green cuttings did not decrease below 72%. The average rooting rate of rootstock cuttings was 85.7%. This indicates that these rootstocks can be used for industrial cultivation of stone fruit seedlings.


Introduction
The world production of cherries and sweet cherries is estimated at 3 million tons, of which about 2 million tons is the production of sweet cherries and 1 million tons is the production of cherries, with an average fruit yield of 52.9 q/ha [1]. The fruits of cherries and sweet cherries contain a large amount of vitamins and minerals, fiber, fructose, which are necessary for a person [2]. To meet the needs of the population with high-quality fruits in fresh and processed form according to a scientifically based nutritional norm (85 kg of fruit per person per year), it is necessary to significantly increase the production of these products [3]. The solution of this problem is carried out due to the intensification of the fruit growing industry [4]. At the present stage, intensification is based on the introduction into production of new highly productive varieties of fruit species with limited growth, new designs of tree crowns, as well as on the use of low-growing clonal rootstocks [5].
One of the most important elements of technology in creating intensive gardens is highquality planting material, which ensures optimal growth and development of trees in the garden, the productivity of plantings and the payback of the funds invested in production [6,7]. Propagation of stone fruit crops on clonal low-growing rootstocks is the main method for the production of seedlings in the advanced countries of the world. Trees on clonal rootstocks quickly bear fruit and are resistant to various stressful soil and climatic conditions [8].
The technology of green cuttings can significantly increase the coefficient of plant reproduction. In addition, own-rooted trees in the garden have certain advantages over grafted ones. However, there is evidence [9] that not all cherry varieties have the same ability to regenerate adventitious roots. The expediency of growing own-rooted seedlings of cherries and sweet cherries from green cuttings for certain groups of varieties remains relevant to this day.
Not all stone fruit species, including cherries and cherries, when propagated by green cuttings, are able to form adventitious roots on the lower cuts [10]. A general assessment of the effectiveness of the method of propagation of cherries and sweet cherries from green cuttings is the rooting of green cuttings and the yield of standard seedlings. Our studies with varieties of cherries and sweet cherries revealed that the level of rooting of green cuttings in them ranges from 15.4 to 83.5%.

Materials and methods
The study was conducted at the scientific experimental base of the Tashkent State Agrarian University in 2019-2020. As an object of study, eight varieties of cherries and cherries, as well as nine types of vegetatively propagated rootstocks, were used.
To determine the morphological ability of varieties and rootstocks, green plant cuttings were harvested from mother plants in the early morning hours. Cuttings were harvested with two or three internodes. The lower cut was carried out directly under the kidney, the upper one was 1.5-2.0 cm above the upper kidney. The cut cuttings were tied into bundles and labeled with the indication of the breed variety and the type of rootstocks.
Harvested green cuttings of varieties and rootstocks were soaked in a solution of indolylbutyric acid at the rate of 20 mg/l of water and kept in the prepared solution for 16-18 hours. Planting cuttings in an artificial substrate was carried out in the evening. In each variant of the experiment, 100 cuttings were planted in the substrate. The experiment was repeated three times.
During the rooting of cuttings and the development of varietal seedlings of cherry, sweet cherry and rootstocks, such records and observations were carried out as the beginning and mass rooting, the number of growths formed on plants, the diameter of the root neck of plants, the formation of the root system, the marketability of grown rootstocks and varietal seedlings. The experimental material obtained as a result of the study was subjected to statistical processing according to the Dospekhov method [7].

Results and discussion
For cherry varieties, the rooting rate of cuttings is 30.2-83.5%, sweet cherries are much lower -15.4-30.1%.
Cherry varieties Shpanka black, Podbelskaya and Shubinka can be used both for growing rootstocks and varietal seedlings from green cuttings. Unlike cherries, cherry varieties with very low rates of rooting of green cuttings are not advisable to use for the industrial cultivation of rootstocks and varietal seedlings (Table 1). For these purposes, it is necessary to use other biological groups of fruit plants. Studies have shown that the yield of self-rooted cherry and sweet cherry seedlings depends on individual varietal characteristics. Thus, the highest yield of standard plants was observed in easily rooted varieties. The output of marketable seedlings from the number of cuttings planted for rooting in the studied years in cherry varieties averaged 50.5-69.5%. In sweet cherry varieties, this quality indicator of rooting did not exceed 18.5-22.5%. That is, varieties of sweet cherries for propagation by green cuttings are not suitable.
The development of rooted plants, the yield and quality of self-rooted seedlings of cherry and sweet cherry, in our opinion, depend on the genetic abilities for rhizogenesis of each variety or group of varieties, as well as on their biological characteristics of plants.
Along with ensuring the rapid reproduction of varieties, by selecting certain grafting combinations, it is possible to significantly regulate the processes of growth and development of a fruit tree, its adaptability to soil and climatic conditions, the time it takes to bear fruit, the yield and quality of fruits.
As shown by previous experience in rooting cherries and especially sweet cherries with green cuttings, it can be seen that most of the varieties do not have sufficient ability for adventitious root formation. This makes it necessary to propagate the plants by grafting on rootstocks. At the same time, some varieties are easily propagated by green cuttings.
In recent years, in our country, clonal vegetatively propagated rootstocks, including those for cherries and sweet cherries, have become increasingly widespread. The experimental data given in Table 2 on the rooting rate of green cuttings of clonal rootstocks indicate that most of them have a high ability for root system rhizogenesis. However, it should be noted that the rootstock rootstocks P-1, P-3, PN, VTS-13, ORP-3 and 11-59-2 had the highest rooting rates and amounted to 87.6-94.3%. Of all the studied rootstocks, such vegetatively propagated rootstocks as PN, ORP-3, VSL-2 (Krymsky-5) and SAV-6R had the highest rooting ability of cuttings, in which this quality indicator was 93.1-100.0%.
The above rootstocks were further our research. The study of the rooting rate of green cuttings of clonal rootstocks when planted in the substrate on June 1 revealed the highest rooting rate of new promising rootstocks P-3, P-7, PN, VSL-2 (Krymsky-5) and SAV-6R. For these clonal rootstocks, the quality index of rhizogenesis of green cuttings was 80.7-91.2%. Rootstocks P-3 had the best indicators of rooting of cuttings, lower ones -for rootstock VP-1.
It should be noted that the majority of rooted cuttings by the end of the growing season had a well-developed root system and an increase in the central shoot. In the process of rooting, the lateral buds awakened more intensively in the rootstocks P-3, P-7, VSL-2 (Krymsky-5) and SAV-6R, which is a positive sign, since the presence of leafy shoots in the cutting contributes to the development of a stronger root system and increase in root collar diameter.
A study on the rooting of green cuttings of rootstocks in the second planting date of the cuttings -July 1, revealed a decrease in the quality of rooting by the first planting date for the rootstock VP-1 by 26.9%, P-3 by 7.7, P-7 by 8.5, PN by 6.2%, VSL-2 (Krymsky-5) by 9.5% and SAV-6R by 14.3%. That is, the quality of rooting from the first term of planting cuttings to the second (July 1) decreased by an average of 12.3% (Table 3). The rooting rate of the cuttings of the tested rootstocks in the third period of cuttings (August 1) revealed the lowest rates of rhizogenesis of green cuttings. For rootstocks P-3, P-7, PN, VSL-2 (Krymsky-5) and SAV-6R, by the first date of planting green cuttings, it decreased by 1.9-2.8 times, and for rootstock VP-1 by 7, 6 times. That is, the most acceptable time for grafting green shoots of clonal stone rootstocks for plums and cuttings is June 1, when it coincides with the active growth of mother shoots.
In another experiment, we studied the issues of optimizing the layout of rootstock cuttings. The study found that an increase in the feeding area has a different effect on the rooting and development of rootstocks from green cuttings. So, with an increase in the scheme of planting cuttings from 25 cm2 (5x5) to 50 cm2 (5x10 cm), the rooting rate of all clonal rootstocks increases the quality of rooting of cuttings. A further increase in the feeding area to 100 cm2 ensured an increase in rooting and improved development of rooted cuttings. This made it possible to obtain more cuttings with a good growth of shoots. In contrast to schemes with an increased feeding area, the main number of cuttings formed a significant increase without interfering with the development of neighboring plants. In the process of rooting of green cuttings of clonal rootstocks with a minimum feeding area, the buds, especially the lateral ones, awakened weaker and the emerging young shoots of plants oppressed each other. Therefore, the quality of the rooted material was different. This, apparently, is also associated with different intensity of root formation processes. The cuttings that formed roots faster were in more favorable nutritional conditions, and they continued to develop faster, inhibiting the growth of other plants. As for the development of cuttings with more sparse planting patterns (10x10 and 15x15 cm), their height, growth and development of the root system were significantly better.
Thus, when rooted in conditions of artificial fog, the green cuttings of all the rootstocks studied in the experiment showed a high ability to root formation. An increase in the feeding area of the cuttings increased the percentage of rooting for all rootstocks, and also contributed to the improvement of the quality of the rooted material. Green cuttings rooted well in almost all feeding areas. However, with a minimum planting scheme of 25 cm2 (5x5), the rooting of cuttings was significantly worse. This is due to a supersaturation of moisture in artificial substrates where green cuttings were planted for rooting. The root system of rooted cuttings in this case rotted.
The study showed that the optimal scheme for planting green cuttings of rootstocks is 5x10 cm (Table 4). In our studies, we also studied the dependence of root formation in green cuttings of clonal rootstocks in connection with the size of the cutting. It has been established that with a decrease in the leaf surface, as well as the mass of the leaves of the cutting, in all variants of the experiment, the quality of the rooting of the cuttings, the number of cuttings with growth, the diameter of the conditional root neck, as well as the mass of the stem, leaves, roots, and in general, the weight of the entire cutting decreases proportionally. . However, for clonal rootstocks VP-1, P-3, VSL-2 (Krymsky-5) and SAV-6R, the differences were insignificant between the variants with 4-and 3-node cuttings, when there was a slightly better development of the root and aboveground systems compared to with options where the cuttings were cut into 2-nodal. Rootstock P-7 also showed a deterioration in similar indicators between variants with a decrease in the number of nodes in the cuttings, but these differences were more even (Table 5). The study of the further development of rootstocks after planting in the first field of the nursery with the subsequent cultivation of varietal seedlings of cherry and sweet cherry on them showed that, unlike VP-1 and P-7, rootstocks P-3, VSL-2 and SAV-6R in the first half of the growing season weakly formed the above-ground system, therefore, by June 15, a small number of rootstocks were suitable for budding in a T-shaped incision.
Rootstocks VP-1 and P-7, in contrast to VP-1, in terms of the development of the aboveground system, regardless of the type of cutting, were completely suitable for budding by the first growing season. It should be noted that the differences between the variants, depending on the type of rooted cuttings in terms of the diameter of the bole, for all rootstocks persist until autumn.
All this indicates that root formation in green cuttings of clonal rootstocks VP-1, P-3, P-7, VSL-2 and SAV-6R is determined by the functional activity of the leaves. With a decrease in their number and, accordingly, x area and mass, as well as the mass of the entire cutting, a weaker development of the adventitious root system and further development of rooted cuttings are observed.
Analysis of the changes in the main indicators of rooted cuttings of the clonal stock VP-1, depending on their quality, it can be seen that a significant development of the bole in diameter falls on the period between the first and second terms of budding, in the second half of July. As a result, the assimilation apparatus increases, which affects the development of the entire aerial parts of plants.
Approximately the same data were obtained when studying the development of rooted cuttings of clonal rootstocks P-3 and PN. The differences consisted only in the fact that they had a slightly higher survival rate of rooted cuttings; further development of plants during the entire growing season was slightly contained compared to similar variants of other rootstocks. Probably, the long-term slow growth of these rootstocks is a consequence of the genetic characteristics of P-3 and PN rootstocks. These rootstocks, due to the high awakening of the buds along the entire height of the plant, form many side shoots, which creates certain technical difficulties in preparing boles for budding.
Data on growth rates and readiness for budding at different times, similar to the rootstock VP-1, were obtained in the study of the clonal rootstock P-7. Plants frolicking from rooted cuttings differed in the maximum growth of the aerial part and the diameter of the bole at the beginning of budding. Further development of stone fruit horticulture will occur not only through the use of lowgrowing vegetatively propagated rootstocks for growing varietal seedlings, but also through the use of seed rootstocks. So, as the trees grown on their basis have a good development of the taproot and lateral roots of the first and second orders, penetrating to a depth of 3.0-3.5 meters. This sign should be taken into account when laying gardens in the foothill-mountain zones of the republic.
One of the main factors in the cultivation of seed rootstocks of cherries and sweet cherries is the germination of seeds and the evenness of the morphological development of rootstocks.
As studies have shown, all the vegetatively propagated uterine rootstocks studied by us have a fairly high laboratory and field germination, as well as good development. So, by the period of summer budding, about 76.7% of cultivated cherry and plum rootstocks reach the standard requirements.
The experiments carried out by us revealed certain qualitative differences in the germination of seeds of varietal plants and vegetatively propagated types of rootstocks. The germination of seed material of varietal plants was 2.7 times lower than those collected from uterine vegetatively propagated plants (Table 7). In our experience, a study was also conducted to study the effectiveness of methods for growing rootstocks of cherries and sweet cherries by seed and propagation by green cuttings.
From the experimental data in Table 8 it can be seen that the field germination of seeds of varietal and vegetatively propagated plants is quite high from 31.6 to 60.4%. The rooting rate of vegetatively propagated rootstocks with green cuttings according to the experimental variants was high and ranged from 82.7 to 95.5%. In rootstocks propagated by seed, this trait was significantly lower (31.6-60.4%). In vegetatively propagated rootstocks, a high degree of rooting of green cuttings was combined with intensive development of plants during the growing season (Table 8). In the cherry varieties Shubinka, Podbelskaya and Lyubskaya, the lower seed germination was compensated for by a slightly better rooting quality of green cuttings. However, the best quality of the development of rootstocks in the experiment differed in the variants of the experiment, where rootstocks of cherries and sweet cherries were grown from green cuttings of vegetatively propagated rootstocks.
Thus, summarizing the conducted studies, it can be stated that in the fruit nursery it is necessary to grow seedlings of cherries and sweet cherries both on seed and vegetatively propagated rootstocks. This is due to the fact that when planting cherry and sweet cherry orchards in the foothill-mountain zones, it is necessary to use seedlings grown on seed stocks. For laying gardens in flat conditions, it is more rational to use seedlings of cherries and sweet cherries grafted onto low-growing vegetatively propagated rootstocks.