Clonal rootstocks of apple trees are one of the main components of intensive horticulture, and they play an important role in regulating tree growth, yield, fruit quality, and resistance to biotic and abiotic stresses. In the two-year monitoring survey reported here, eleven rootstocks mainly used for cultivar grafting in Kazakhstan were assessed for fire blight resistance, taking genetic background into consideration. The loci FB_F7 on LG7 and FB_MR5 and RLP1 on LG3 were analyzed on the basis of SCAR and SNP markers. The rootstocks ‘Geneva 41’, ‘62-396’, and ‘Geneva16’, bearing resistant alleles for five markers (AH0JFXM, AH21B92, AH4AAGA, AH5I8MI, and AH6R6SQ), four markers (AH0JFXM, AH21B92, AH4AAGA, and AH5I8MI), and one (AH4AAGA) SNP marker, respectively, were not infected during the monitoring period despite weather conditions in 2022 being favorable for the development and spread of Erwinia amylovora. No connection was identified between the presence of a resistant allele for the AE10-375 marker and fire blight resistance responses. This is the first study to evaluate the fire blight resistance of foreign and local rootstocks grown in the Kazakhstan southern region.

Fire blight of fruit crops is one of the most dangerous diseases for apple trees and other plants of the Rosaceae family, and in Kazakhstan, it is subject to quarantine. To study the spread of fire blight, a phytopathological evaluation of 59 apple varieties of domestic and foreign breeds was carried out in various regions of the south and southeast of Kazakhstan while also considering climatic conditions. The susceptibility of an apple tree to fire blight is influenced by the climatic conditions prevailing in a particular fruit region of Kazakhstan. Samples were collected from various varieties of apple trees with fire blight symptoms for molecular genetic analysis. The phytopathological evaluation and results of the PCR analysis made it possible to identify the causative agent of the disease and its spread to apple varieties in the main fruit regions of Kazakhstan. A molecular study of the resistance to the fire blight pathogen was carried out using the most effective molecular markers. A set of 10 (FBE-1_Y320; FBE-2_Y192; FBE-2_Y495; FBE-2_Y551; FB-MR5-K35; FB-MRS-R240; FB-MR5-R249; FB-MR5-rp16k15_M106; RLP1a; and RLP1b) SNPs was selected, including SNPs reported to be associated with three trait loci, as well as the two markers AE10-375 and GE-8019. Interestingly, the SNP analysis revealed that for all ten markers linked to fire blight resistance, the genotypes of all 59 apple cultivars were identical. No differences in the presence or absence of these markers were observed among the studied varieties. The 26 apple varieties of domestic and foreign breeds most resistant to fire blight were identified in the molecular analysis using the markers AE-375 and GE-8019. Among the studied 59 apple varieties, 23 varieties were identified using the AE-375 marker and 7 varieties with the GE-8019 marker. Samuret, Honeycrisp, Pinova, and Red Topaz were found to be resistant using markers AE-375 and GE-8019. The most promising apple varieties for further breeding for resistance to fire blight programs were selected.

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 (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.

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.

The most widespread and effective method of protecting walnut trees from diseases is through chemical treatments. With the increasing variety of fungal pathogens affecting walnut trees in the southern zone of fruit production in Kazakhstan, there is a need to study the effectiveness of fungicides against these pathogens. Therefore, laboratory and field studies were carried out to evaluate the effectiveness of several fungicides against the most common diseases of walnut trees caused by Fusarium and Alternaria fungi. The effectiveness of fungicides with different mechanisms of action was studied for the first time. The fungicides evaluated were Score (difenoconazole, 250 g/l), Horus (cyprodinil, 750 g/kg), Stroby (kresoxim-methyl, 500 g/kg), Luna Tranquility (fluopyram, 125 g/l + pyrimethanil, 375 g/l) against walnut diseases in the southern zone of fruit cultivation in Kazakhstan. The results of both laboratory and field experiments showed that the most effective fungicide against fungal pathogens on walnut was Score (difenoconazole, 250 g/l). Stroby (kresoxim-methyl, 500 g/kg) also demonstrated over 80% biological efficacy against Alternaria alternata. The results of this study will assist local growers in managing various fungal diseases in walnut plantations.