Walnuts are considered recalcitrant to tissue culture, with a great genetic determinism on all stages of micropropagation; while other factors, also with great impact, become more complicated with the reproduction of newly realized varieties. In this research, a holistic approach aimed to determine the influence of genotype and the nutritive formulation throughout the whole cycle of micropropagation of four Persian walnut varieties (Juglans regia L.) was presented. During the in vitro establishment it was determined that besides genotype and culture medium, the effect of collection season and the likely interaction amongst factors had a great influence on the successful introduction of all four genotypes. However, all cultures were affected by a deep decay, being necessary the introduction of ethylenediamine di-2-hydroxyphenyl acetate ferric, as iron source, and Phloroglucinol in both Murashige and Skoog (1962) and the corrected Driver and Kuniyuki (1987) formulations. These modifications allowed the stabilization of cultures, maintaining thereafter a steady quality. Either proliferation, rooting and ex vitro survival of four clones were affected by the culture medium, obtaining the best results with the corrected Driver and Kuniyuki (1987) formulation. Finally, in vitro plants produced from all clones were acclimated with high survival rates (75.9–91.1% for the best culture medium), depending of clone and the culture medium used. Microsatellite analysis showed that micropropagated plants maintained the same genetic profiles of their corresponding donor trees. These results might contribute to deepening of the understanding of factors that determine the success of micropropagation of walnuts, and the extents of its influence; whereas, it sets the basis for the commercial micropropagation of all four clones.

Walnut (Juglans regia L.) is a significant nut crop in the southern regions of Kazakhstan; however, its productivity is substantially limited by fungal and bacterial diseases. Therefore, a phytopathological investigation was conducted in 2023–2024 in the Almaty and Turkestan regions, including field monitoring, pathogen isolation, molecular identification, and pathogenicity testing. Field monitoring revealed that symptoms of brown spot, walnut canker, walnut blight, bacterial blight, and crown gall were widespread. The overall disease incidence ranged from 8% to 30%, while the disease severity index varied from 15% to 70% across the surveyed sites. Pure cultures of pathogens were isolated from 69 samples, and their morphology was characterized. Molecular identification through sequencing of universal genetic loci (the internal transcribed spacer for fungi and 16S ribosomal RNA for bacteria) revealed the presence of the fungal species Alternaria alternata and Fusarium incarnatum, as well as the bacterial species Pantoea agglomerans and Xanthomonas arboricola pv. juglandis. Pathogenicity testing confirmed the virulence of the identified pathogens, which induced characteristic symptoms of brown spot, walnut canker, and walnut blight, consistent with those observed in the field. These findings have considerable practical significance for improving phytosanitary monitoring and protection systems in walnut plantations, thereby facilitating disease outbreak prediction and the development of effective quarantine measures.

Industrial cultivation of nut crops in the Republic of Kazakhstan is promoted by favourable soil and climate conditions, especially in the southern region, which makes it possible to obtain high yields of this valuable plant in the future. Significant damage to the yield of nut crops is caused by diseases, protection of plantations from which is one of the main measures aimed at increasing their productivity. The most important issue in cultivation of nut crops is its protection from bacterial and fungal pathogens. In Kazakhstan purposeful researches on studying species diversity of diseases and pests of nut crops have not been carried out. The novelty of the conducted research is in the fact that for the first time in Kazakhstan fungal and bacterial diseases of walnut in the conditions of the southern zone of fruit growing on the basis of microbiological and molecular-genetic methods were identified. The results of research showed that the majority of isolated pathogens are fungi, as well as several species of bacteria causing diseases of walnut. In total, 4 genera of fungi were isolated: Alternaria, Fusarium as causative agents of fungal diseases; Aspergillus, Penicillium as secondary infestation; also 2 genera of bacteria: Pantoea, Pseudomonas as causative agents of bacterial diseases. Molecular identification of fungal and bacterial pathogens by PCR based on genomic DNA showed that the studied walnut samples were identified as phytopathogenic fungi: Alternaria alternata, Fusarium solani, as well as phytopathogenic bacteria: Pantoea agglomerans, Pseudomonas syringae, Pseudomonas oryzahabitans. The conducted research results will allow to make up a system of protection of walnut from harmful diseases in order to increase the productivity of plantations.

Walnut is one of the most common nuts in many countries of the world. It is used in cooking and in traditional medicine. Walnut cultivation on an industrial scale in Kazakhstan began only in 2016-2017, so Kazakhstan scientists in this field do not yet have any scientific experience. The article presents the results of studies on the influence of the nutrient medium compositions Murashige-Skoog and Driver-Kunzhuki on the microclonal propagation of different genotypes of the walnut Juglans regia L. Two varieties were selected as mother plants: the Uzbek variety Ideal and the Chinese variety Liaohe-1, adapted in the southeast Kazakhstan. In the course of work, we compared the growth rate of walnut shoots of two varieties on nutrient media Murasige-Skoog (MS) and Driver-Kunzhuki (DKW) with a concentration of 6-benzylaminopurine (BAP) of 1 and 1.5 mg / l. After a month of cultivation of shoots, positive growth dynamics was observed only on MS medium. On plants of both varieties, the growth rate was slow on DKW medium, the plants had yellow leaves, some shoots blackened and perished. To obtain high-quality material, as well as to increase the growth rate of shoots, DKW medium was supplemented with FeEDDHA (119 mg / L) and phloroglucinol (50 mg / L). As a result of phenological observations: the height of the main shoot, the number of internodes, the formation of additional shoots, and the state of the plants, it was found that the best nutrient medium for microclonal propagation of walnut Ideal and Liaohe-1 is a modified DKW medium. MS can only be used at the initial stage - an introduction to in vitro culture.

Walnut blight is a harmful disease that affects nut crops. It is caused by the bacterium Pantoea agglomerans and has become widespread in recent years, posing a serious threat to walnut plantations. The disease not only destroys more than half of the crop, but also causes bark cracking and slow crown desiccation, which can lead to further infections. One of the most important requirements for modern varieties of agricultural plants, including nut crops, is an increased level of resistance to diseases. In Kazakhstan, there is currently no data on the spread of diseases of nut crops and resistance of varieties to harmful diseases. This makes it difficult to recommend a suitable variety for industrial and private nut orchards. Ipmroving the breeding process and increasing the productivity of walnut plantations, it is extremely relevant to assess the resistance of varieties to the most dangerous pathogens. For the first time in Kazakhstan, a two-year monitoring study was conducted to assess the resistance of promising walnut varieties and forms to the Pantoea agglomerans, taking into account the prevailing weather and climatic conditions. The study was carried out on 23 varieties and forms in the main fruit-growing regions of the country. It was found that the walnut blight caused by the bacterium Pantoea agglomerans annually damages walnut plants, and the degree of disease damage depends on the prevailing weather and climatic conditions. The research results revealed that the Moldavian variety - Kazaku showed high resistance to walnut blight. Other resistant varieties are Miroslava, Ovidiu, Germisara, Yarivski, Peshanski, Kogylnichanu, 185, Lipin 2, Liaohe, Fernor, Plin, and Kishinevski. These varieties showed minimal damage, not exceeding 2 points, during the years of observation. These varieties are recommended as suitable varieties for increasing the productivity of industrial and private nut orchards and improving the breeding process.

. Currently, Kazakhstan has increased interest in nut crops, especially walnuts, which bring stable yields in the most favorable areas for it. Walnut is a valuable product, and its industrial cultivation in the southern regions of the Republic has a certain perspective. Biometric observations, accounting for productivity and average weight of the fetus and nucleus, and phenological observations were carried out. The General condition of plants was also assessed. Selected and studied 3 forms established during the period of expedition research in the Almaty region and two in Turkestan. Observations of promising forms of walnuts in two regions have shown that the previously selected forms show a fairly high adaptive stability and yield stable yields of high enough quality. It should also be noted that the fruiting of 2018 Almaty forms took place after winter drops to -33C and 10 days of steady cooling at the level of 23-28C. This allows us to include all three promising forms, Aliyar (Issyk), Enbekshikazakh district, Krivenok from Kyrgyzaulda and from the Seidaliev estate, Karasay district. The largest of them is Aliyar, with an average weight of more than 13 g, a core yield of 51%, and not very strong shell. The seidali form is the least large-fruited and does not meet the requirements for the size of the fruit. The form of Kyrgyzaulda also does not reach 11 g, but it has almost a paper shell and an excellent taste of the core, which can even be attributed to dessert. The unique properties of the Turbat nut from the 19th century continue to surprise. No frost damage and saving in more. more than 100 years of age of physiological activity. This year's yield was higher, while maintaining the size of nuts with an average weight of 13 g. Further work is planned to introduce it to culture in vitro for micro-propagation and prepare documentation for recognition as a breeding achievement of global significance.