Relevance.The development of F1 hybrids distinguishing it from cultivars by high productivity, plant uniformity in ripening date, fruit sizes and quality is the promising trend in breeding program in cucumber (Cucumis sativus L.).The aimof the study was to optimize the gynogenesis induction condition in culture of unpollinated ovules in vitro in order to broad the generation of new breeding forms and to accelerate homozygous line production.Materials and methods. Eight promising cucumber accessions from Laboratory of Cucurbit Breeding and Seed Production (FSBSI FSVC) were taken for the study. The protocol developed in Laboratory of Biotechnology (FSBSI FSVC) for production of doubled haploid in Cucurbitaceae family was used in the experiment. The medium IMC with 30 g/L sucrose and 7g/L agar supplemented with 200 mg/L ampicillin and 0.2 mg/L thidiazuron (TDZ) was applied to induce gynogenic development.Results. The half-open bud or flower was shown to be the most suitable to be taken as an explant for cultivation. Highest number of embryo-like structures in all accessions developed from ovaries 2.1-2.6 cm long. Exposure to sterilization solution of sodium hypochlorite for 15 min made ovary wall softer and ovules can be then easily extracted without traumatizing. The traumatized ovule resulted in inhibited gynogenic development. Embryoids and calli had developed in all studied cucumber accessions, but well-formed plants were only obtained in six accessions. In total 26 plants were produced. The maximum gynogenesis induction equal to 63.1% was achieved in accession 1810. Maximum number of plant produced was twelve in accession 1763, but the greatest plant outcome 7.7% of the ovules with induced gynogenesis was observed in accession 1807.

An important stage in doubled haploid (DH) production is to evaluate and to differentiate the ploidy level of regenerant plants at least two–three times during the technology. Therefore, rapid and reliable methods are necessary for particular species taken into the technology. In this study, Cucurbita pepo regenerants obtained through unpollinated ovule culture in vitro were evaluated including three different methods: direct chromosome counting in apical meristems, flow cytometry of the cell nucleus, and estimation of morphological parameters of the abaxial epidermis. Methods were optimized for each of three evaluations, and main criteria were determined for ploidy level differentiation. As a result, four ploidy levels, namely, 2n, 3n, 4n, and 8n, were defined among regenerant plants adapted to ex vitro conditions, while true haploids were only found among plants that remained in the in vitro culture. In total, 32.35%, 26.47%, 33.82%, 4.41%, and 2.94% of regenerant plants of courgette and patisson were diploid, triploid, tetraploid, octaploid, and aneuploid, respectively. According to results of flow cytometry of the cell nucleus, two cytotypes in diploid samples with DNA content of 2C = 1.07 ± 0.03 pg for courgette belonging to subsp. pepo and 2C = 0.95 ± 0.03 pg for patisson samples belonging to subsp. ovifera were revealed. The images of metaphase chromosomes of haploid, triploid, and tetraploid C. pepo specimens obtained using the propion–lacmoid chromosome staining method were presented for the first time. Parameters of abaxial epidermis in diploid samples of courgette and patisson grown in open-field and greenhouse conditions were described and compared. It was shown that the most robust parameter not depending on external factors was the number of chloroplasts in stomatal guard cells, which contained 9.41 to 11.31, 14.84 to 16.3, and up to 17.58 chloroplasts in diploid, triploid, and tetraploid samples, respectively. The application of several methods for estimation enables avoiding the misidentification of ploidy levels in adapted regenerant plants produced with the use of DH technology.

Doubled haploids have been widely used worldwide in breeding programs and fundamental research as valuable homozygous material for about 100 years. The species Cucurbita pepo L. are represented by a huge variety of forms, include highly productive vegetable crops and have a wide distribution in the world. Despite the great economic importance, the creation of effective protocols to ensure stable production of doubled haploids in this species remains an urgent task. DH plants are of interest not only because of the acceleration of the breeding process, but also because of the realization of the huge potential of gametoclonal variability inherent in this highly polymorphic species. In this review, we analyzed the main technologies used for obtaining doubled haploids in vegetable crops of C. pepo: parthenogenesis in situ stimulated by treated/irradiated pollen, gynogenesis in vitro (unpollinated ovule culture in vitro) and androgenesis in vitro (anther/microspore culture in vitro). An analysis is presented of the research carried out from the beginning of the discovery of haploid plants to the current advances and evaluation of the prospects in the field of DH plant production. The main critical factors influencing the efficiency of each technology and its individual steps are considered. The developed technology of doubled haploids obtaining using non-pollinated ovary culture in vitro is presented. This technology allows to obtain up to 55 embryoids per one cultivated ovary (28 embryoids/ 100 cultivated ovules) To introduce haploid technologies into the breeding process it is necessary to evaluate the obtained plants for ploidy level. The use of direct counting of chromosomes in apical cells may present a certain difficulty in this species due to their large number (2n=40) and their small size. Depending on the level of laboratory equipment, ploidy determination using flow cytometry of cell nuclei and counting the number of chloroplasts in stomatal guard cells in the epidermis of the abaxial side of the leaf may be more convenient methods. The prospects for the use of molecular markers for assessment for homozygosity in DH technologies used, including C. pepo, are discussed in the review.

Implementation of cell technologies has essentially improved the plant breeding process in agricultural crops in the world. The production of pure lines in cultivated crops, particularly among cross-pollinated species such as cucumber (Cucumis sativusL.) requires much time, labor and expense. Thus, the use of DH-plants for production of fully homozygous lines for one year becomes a very promising method for near cucumber breeding program. The major factor limiting the wide use of DH is a lack of effective protocol for large-scale plant production. In this review the historical facts with description of three main methods of DH-plant production were presented. By now these three methods have been such as parthenogenesisin situinduced by pollination with irradiated or chemically treated pollen; androgenesisin vitroincluding anther and isolated microspore cultivationin vitro; gynogenesis through ovule cultivationin vitro. Comparative analysis of published data with regard to the efficiency of the technology for DH-plant production was shown as well as advantages and limitations of each technology were described.

Relevance. Powdery mildew is one of the most common and harmful diseases of cucumber (Cucumis sativus L.) in open and protected ground. Moreover, in the closed ground, the harmfulness is higher than in the field. The yield of cucumber, due to the defeat of plants by powdery mildew, decreases by 30-50%, and in some cases by more than 70%. The creation of modern cucumber hybrids is impossible without the constant involvement in the breeding process of new sources of economically useful traits, including resistance to real powdery mildew. It is very important to combine in one line both a high degree of parthenocarpy, and the female type of flowering, and resistance to the most harmful diseases. We tried to solve this problem in our work.Materials and methods. The experience was laid in 2018-2022 in the Odintsovo district of the Moscow region on the basis of the head institution of the Federal State Budgetary Scientific Institution Federal Scientific Vegetable Center (FSBSI FSVC) in the conditions of a spring ground greenhouse of the Block type, on a natural infectious background. On the basis of the laboratory of breeding and seed production of pumpkin crops, 27 collectible and about 50 breeding samples of parthenocarpic cucumber were studied. The article presents an assessment of the resistance to this powdery mildew of 36 of the most aligned and most valuable cucumber breeding samples in terms of a complex of economically useful features. 2-3 families, 6 plants in each, were evaluated for each sample for 2 years. During the entire growing season, the intensity of powdery mildew damage was assessed on a four-point scale and the spread of the disease in %.Results. Among the collection samples of cucumber, on a natural infectious background, two hybrids of the agrofirm BEJO ZADEN B.V. were not affected by powdery mildew: Amur 1801 F1, Artist F1, a hybrid without a name of the agrofirm MONSANTO HOLLAND B.V., conventionally named – Semenis F1 and hybrid Kibria F1 of the agrofirm RIJK ZWAAN. To a small extent, less than one point, they were amazed: Orpheus F1, Merengue F1, Marinda F1, Masha F1, Othello F1, List F1, Adam F1, SV 4097 F1 and Krasotka F1. 11cucumber breeding samples selected in previous years of research on a complex of economically useful signs that were not affected by this disease during 2 years of research were identified. Work will continue to evaluate these lines for resistance to real powdery mildew on an artificial infectious background.

Оценка рассады огурца на устойчивость к полеганию по длине подсемядольного колена