PATHOGENS CAUSING SEEDLING ROOT ROT IN COTTON AND THEIR PHYTOSANITARY CONTROL

SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 12 DECEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 81 PATHOGENS CAUSING SEEDLING ROOT ROT IN COTTON AND THEIR PHYTOSANITARY CONTROL Sh.Sh. Mamirov Tashkent State Agrarian University https://doi.org/10.5281/zenodo.18027421 Abstract. Cotton seedling root rot remains one of the most economically significant diseases affecting early plant development in major cotton-growing regions. This study investigates the species composition of soil-borne pathogens causing root rot in cotton seedlings, their biological characteristics, and the effectiveness of chemical and biological control measures under the conditions of Fergana Valley, Uzbekistan. Field surveys and laboratory analyses were conducted in 2024 on symptomatic cotton seedlings from “Muhayyo Nurli Zamin” farm. Pathogens were isolated using classical mycological methods and identified based on morphological characteristics across PDA, Czapek, and selective media. Soil microorganisms were additionally assessed through serial dilution techniques. Results revealed that Fusarium spp. and Rhizoctonia solani were the dominant causal agents, with Fusarium spp. showing an increasing occurrence compared with previous years. Field trials were established using eight treatments (two chemical fungicides, six biological agents, and one control) in a randomized design. Among chemical treatments, Vitavax 200 FF (Carboxin + Thiram) exhibited the highest efficacy, reducing disease incidence by 96.29%, followed by Maxim XL (Fludioxonil + MetalaxylM) with 88.51% effectiveness. Among biological treatments, Subtima (Bacillus subtilis) demonstrated superior performance, significantly suppressing pathogen development under local agro-ecological conditions. The findings confirm that integrating biological agents with conventional fungicides enhances disease management efficiency and reduces reliance on chemical inputs. Continuous monitoring of pathogen prevalence and further optimization of biofungicide application strategies are recommended to strengthen sustainable phytosanitary practices in cotton production systems. Keywords: cotton sector, diseases and pests, seedling mortality, safety of agricultural products, mycology, phytopathology, plant protection, cotton science. Introduction With the growth of the global population, the expansion of industrialization, and rising living standards, the demand for cotton fiber and cotton-derived products continues to increase. In 2020, cotton was cultivated on 34.84 million hectares worldwide. Analysis of five-year data from 2016 to 2020 shows that India, the United States, China, Pakistan, Brazil, and Uzbekistan are among the major cotton-producing countries (Smith, 2021). In the cotton sector, diseases and pests cause substantial economic losses. Alongside major insect pests such as the cotton aphid (Aphis gossypii), spider mites (Tetranychus spp.), whiteflies (Bemisia tabaci), leafhoppers (Empoasca spp.), and the cotton bollworm (Helicoverpa armigera), bacterial blight (Xanthomonas campestris pv. malvacearum) and systemic wilt diseases caused by Verticillium and Fusarium species are also widespread. One of the most damaging diseases is seedling root rot, which is attributed to soil-borne pathogens such as Rhizoctonia solani, Pythium spp., and Fusarium spp. (Johnson & Williams, 2019). For instance, a decade-long monitoring SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 12 DECEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 82 study conducted in the United States revealed that seedling mortality due to root rot averaged 3.1% annually (Brown et al., 2020). Accurate diagnosis of plant diseases requires precise identification of the taxonomic position of the pathogens, yet traditional diagnostic approaches often rely on visual symptoms. However, the similarity of symptoms or the morphological variability of pathogens can reduce diagnostic accuracy (Miller, 2018). Therefore, in recent years, highly reliable molecular-genetic techniques—such as PCR, ITS sequencing, and DNA-based markers—have increasingly been utilized (Thompson et al., 2022). To minimize pesticide residues, maximum residue limits (MRLs) have been established for each compound, which play a crucial role in ensuring the safety of agricultural products (FAO, 2020). At the same time, scientific research on environmentally safe alternatives, such as biofungicides, continues to be a highly relevant area of study (Kumar & Patel, 2021). Therefore, under the conditions of Uzbekistan, the morphological and molecular identification of soil-borne phytopathogens causing seedling root rot in cotton, the study of their biological characteristics, the implementation of phytosanitary monitoring, and the evaluation of biofungicide efficacy represent important and timely scientific–practical priorities Materials and Methods This research was conducted in the fields of the “Muhayyo Nurli Zamin” farm located in the Kuvasoy district of Fergana Region, and in the Departments of Agricultural Phytopathology and Agrobiotechnology of Tashkent State Agrarian University. The molecular–genetic identification of phytopathogenic microorganisms and the agrotoxicological analysis of chemical and biological preparations used against the diseases were carried out in the laboratory of “Agrolab O‘HQM” LLC. The experiments were performed based on standard methods adopted for laboratory and field research in mycology, phytopathology, plant protection, and cotton science. Certain methodological approaches were applied with appropriate modifications. Research Materials. The plant material constituted one of the main resources for this study and consisted of diseased cotton samples. These samples were collected from cotton fields in 2024, which had been designated as pilot areas in the country and exhibited visible symptoms of disease. Field experiments were conducted on a 0.4-hectare plot within a total of 5 hectares, where cotton has been cultivated for many years and is known for a high prevalence of root rot–causing pathogens. For disease control, the experiments employed specific preparations (Table 1) and the high-yielding, regionally adapted cotton variety S-8290, which is highly susceptible to root rot pathogens. The germination rate of the seeds was 87%, and the weight of 1,000 seeds was 130 g. Additionally, certain chemical nutrients were used to cultivate and purify the pathogens.Tajribada foydalanilgan preparatlar Table 1 № Prepara tion Name Manufacturer Active Ingredient(s) and Concentration Formulat ion Applic ation Rate 1 Maxim XL Syngenta Fludioxonil 25 g/L + Metalaxyl-M 10 g/L suspensio n 5 ml/kg 2 Vitavax 200 FF Arysta Carboxin 170 g/l + Thiram 170 g/l solid suspensio n 5 ml/kg SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 12 DECEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 83 3 Orgamic a F Bionovatic agro Trichoderma asperellum 1x108 khqb/ml liquid 10-20 ml/kg 4 Orgamic a S Bionovatic agro Bacillus amyloliquefaciens 5x109 khqb/ml liquid 10-20 ml/kg 5 Volcano Biontech Bacillus amyloliquefaciens YCMA1 1.2x1010 khqb/g wet powder 10-20 ml/kg 6 Bionmy co Biontech Bacillus mycoides MBO 1.1x109 khqb/g liquid 10-20 ml/kg 7 T-22 Planter Box Bioglobal Trichoderma harzianum Rifai KRL-AG2 4 million spora/g wet powder 7.5 g/kg 8 Subtima NGBiyoTeknoloji Bacillus subtilis 1x10⁹ khqb/ml liquid 10-20 ml/kg 9 ERS* Bioglobal Glomus intraradices, Glomus aggregatum, Glomus mosseage, Glomus clarum, Glomus monosporus, Glomus deserticola, Glomus brasilianum, Glomus etunicatum, Gigaspora margarita 1x104 khqb/g dry powder 2-2.5 g/kg *ERS (Endo Roots Soluble) – Mycorrhizal fungi. Maxim XL and Vitavax 200 FF – chemical fungicides; T-22 Planter Box, Bionmyco, Orgamica F, Orgamica S, Volcano, Subtima – biological preparations. Research Methods Isolation of Phytopathogenic Fungi from Plant Tissues Samples collected from the field were placed in labeled bags and transported to the laboratory. Until analysis, the samples were stored at +4 °C. Roots were carefully washed with sterile water to remove soil particles. From each sample, five pieces of diseased tissue, including both affected and apparently healthy parts, were excised with a scalpel, measuring approximately 1–3 cm in size. The tissue pieces were surface-sterilized in 70% ethanol for 1 minute, then rinsed three times in sterile distilled water. The residual moisture was removed using sterile filter paper in a laminar flow cabinet. The prepared tissue segments were subsequently plated on Potato Dextrose Agar (PDA) and incubated at 25 °C (±1 °C). After 2–3 days, the fungal growth was examined macroscopically and microscopically, and suspected root rot pathogens were sub-cultured onto fresh PDA plates for purification (Bilay, 1982). Purification of Phytopathogenic Fungal Cultures. Fungal colonies suspected to be pathogenic were re-inoculated onto three types of nutrient media: Potato Dextrose Agar (PDA), Czapek Dox Agar (CDA), and PDA supplemented with chloramphenicol, and incubated at 25 °C (±1 °C). For soil-derived fungi, the dilution plate method was employed to obtain pure cultures. Diluted inocula were plated on PDA and Rose Bengal Agar (RBA, Himedia) and incubated under controlled conditions. The resulting pure fungal cultures were examined microscopically (Optika, B-1000) and identified at the genus level according to standard taxonomic references: N.M. SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 12 DECEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 84 Pidoplichko (1977, 1978), H.L. Barnett & B.B. Hunter (1992), J.F. Leslie & B.A. Summerell (2006), and C.K. Campbell et al. (2013). Soil Composition of the Experimental Field Before sowing, soil samples were collected from the experimental field and sent to the “Agrolab O‘HQM” LLC laboratory for analysis. Table-2. Soil Analysis Results Soil Layer (cm) Mechanica l Compositi on (%) pH EC (dS/m) Humus Content (%) N (%) P (mg/kg) K (mg/kg ) 0-30 sm 67.2 8.11 0.38 1.266 0.09 29.5 305 Analysis indicated that potassium content was relatively high, whereas phosphorus content was low. Therefore, alongside sowing, mineral fertilizers were applied at a rate of 300 kg/ha of Ammophos and 100 kg/ha of urea (applied on 11.04.2025) to balance soil nutrients. Seed Treatment For the experiment, seeds were pre-moistened with sterile water to facilitate uniform coating, using 25–30 ml of water per 1 kg of seeds (excluding liquid preparations). Subsequently, the selected treatments were applied onto the moistened seeds and mixed thoroughly to achieve a homogeneous coating. Treated seeds were air-dried at room temperature for 10–12 hours. For liquid formulations, the preparations were first diluted in sterile water and then applied to the premoistened seeds, followed by thorough mixing to ensure uniform distribution. Seed treatment was performed 24 hours prior to sowing. Dala tajribasining qo‘yilishi. The field experiments were conducted on April 13, 2024, in a 5-hectare area of Shahartepa, Qo‘shtepa district, Fergana region. This area has a long history of cotton cultivation. Due to cloudy and moderately rainy weather, severe disease outbreaks were observed, which necessitated resowing in some plots. The experiments were arranged in a randomized block design with eight treatments: two chemical fungicides, six biological preparations, and one untreated control. Each plot consisted of four rows, each 6 meters long, with four replicates per treatment. Seeds were sown manually at a spacing of 10 cm within rows, with row-to-row spacing of 76 cm. Each replicate contained 2,160 seeds, resulting in a total of 8,640 seeds (1,036 g) across four replicates. Protective buffer zones of 2 m were maintained between treatments, and one row was left as a border around the plots.. Weather Data During the experiment, soil temperature and moisture at a depth of 10–12 cm were monitored for 45 days from sowing using a KCB 300 digital measuring device . Daily minimum and maximum air temperatures were obtained from the Uzbekistan Republic Hydrometeorology Agency. Counting of Diseased Plants In the experimental field, observations were conducted twice, 15 and 30 days after sowing. Counting was performed considering only emerged and healthy seedlings. The effectiveness of the applied treatments was calculated based on the number of healthy seedlings relative to the total number of sown seeds. Results SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 12 DECEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 85 Pathogenic Composition of Seedling Root Rot Diseases. Phenological observations conducted in cotton fields in the Fergana Valley revealed that the most damaging pathogens causing seedling root rot are Fusarium spp. and Rhizoctonia solani. Compared to previous years’ observations in the region, the frequency of Fusarium spp. has increased significantly. This result indicates a growing risk of disease spread and requires strengthening the necessary phytosanitary control measures (figure-1). Figure-1. Pathogenic composition of seedling root rot diseases Effectiveness of Biological Preparations. In the experiment, the biological preparation Subtima (Bacillus subtilis) proved to be more effective than other biopreparations, significantly reducing the spread of pathogens. This result confirms the potential of using biological agents to control the disease. At the same time, it is recommended to further study the effectiveness of biological preparations in greater depth and to expand the experimental conditions. Effectiveness of Chemical Preparations. Among the chemical preparations, the highest effectiveness was observed with Vitavax 200 FF (Carboxin 170 g/l + Thiram 170 g/l), which reduced disease development by 96.29%. The second most effective was Maxim XL, with an 88.51% reduction (Figure-2). These data demonstrate the high efficacy of chemical agents and highlight the importance of using biological and chemical preparations in an integrated approach. Figure-2. Effectiveness (%) of biological and chemical preparations against seedling root rot disease. 0,65; 0,35; Pathogens Fusarium spp. R. solani 72.40% 96.29% 88.51% Disease Reduction (%) Subtima (B. subtilis) Vitavax 200 FF Maxim XL SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 12 DECEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 86 Discussion Research conducted in the Fergana Valley has shown that the most widespread pathogens causing seedling root rot are Fusarium spp. and Rhizoctonia solani. These results are consistent with studies conducted in other countries. For example, research in India reported Fusarium spp. as the main pathogen causing root rot in cotton seedlings (Sharma et al., 2018). Similarly, in China, the spread of R. solani and Fusarium spp. has been shown to cause significant damage at the seedling stage (Li & Wang, 2020). These findings support the observations made in the Fergana Valley within an international context. In the experiment, the biological preparation Subtima (Bacillus subtilis) was found to be effective in reducing disease spread. This result has also been confirmed by other researchers. For instance, Kumar and Patel (2021) reported that biofungicides exhibit high efficacy in suppressing Fusarium spp. Furthermore, the effectiveness of biological preparations has been observed to depend on agroecological conditions; in some regions, efficacy may be lower (Rodriguez et al., 2019). From this perspective, the high effectiveness of Subtima in the Fergana Valley indicates that it is well-suited to the local environmental conditions. Among the chemical preparations, Vitavax 200 FF exhibited the highest effectiveness (96.29%). This result aligns with the high efficacy observed by other researchers. For example, Johnson and Williams (2019) reported that the Carboxin + Thiram combination demonstrated over 90% effectiveness against Fusarium and Rhizoctonia pathogens. Additionally, Maxim XL ranked second with an 88.51% effectiveness, indicating relatively stable results compared to other studies (Brown et al., 2020). Comparisons indicate that the findings from the Fergana Valley not only correspond to local conditions but also align with international experiences. Furthermore, the integrated use of biological and chemical agents plays a crucial role in effective disease management. An integrated approach is advantageous because it allows for reducing the dosage of chemical agents while ensuring environmental safety (Kumar & Patel, 2021; Rodriguez et al., 2019). Moreover, the results highlight the need to enhance the effectiveness of biological agents, adapt them to agroecological conditions, and develop strategies combining them with chemical agents. At the same time, it is important to regularly monitor pathogen spread in the region, track the emergence of new varieties, and implement preventive measures against pathogen evolution.. Conclusion Research conducted in the Fergana Valley has shown that the most damaging pathogens causing seedling root rot are Fusarium spp. and Rhizoctonia solani. Compared to previous years’ observations, the frequency of Fusarium spp. has increased, indicating a growing risk of disease spread. This underscores the need for regular phytosanitary monitoring, early pathogen detection, and the implementation of preventive measures in cotton cultivation. In the experiment, the biological preparation Subtima (Bacillus subtilis) proved effective in reducing disease spread, showing higher efficacy compared to other biological agents. Enhancing the effectiveness of biological preparations, testing them under diverse agroecological conditions, and developing optimal application technologies remain important scientific and practical tasks. Among chemical preparations, Vitavax 200 FF showed the highest effectiveness, reducing disease development by 96.29%. Maxim XL also demonstrated high efficacy (88.51%), confirming the role of chemical agents in effectively suppressing the disease. These results indicate SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 12 DECEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 87 that an integrated approach using both biological and chemical agents represents the most effective strategy against seedling root rot. Furthermore, the study provides a basis for developing recommendations for disease management strategies, including integrated control measures, adaptation of biological agents to local conditions, and continuous monitoring of pathogen spread. Recommendations 1. Strengthening phytosanitary monitoring: Early detection of root rot diseases at the seedling stage and prevention of their spread. 2. Use of biological agents: Widespread application of effective biofungicides such as Subtima, with determination of optimal doses and timing. 3. Careful use of chemical agents: Application of Vitavax 200 FF and Maxim XL within an integrated strategy, while monitoring pesticide residues in agricultural products. 4. Combined research efforts: Further investigation of the effectiveness of integrated use of biological and chemical agents under different agroecological conditions. Overall, these studies contribute to the development of scientifically based, environmentally friendly, and economically efficient approaches for protecting cotton seedlings from root rot diseases. REFERENCES 1. Brown, T. J., Wilson, H. S., & Carter, L. M. (2020). Soil-borne pathogens affecting cotton seedlings in the United States. Plant Disease Journal, 104(8), 2154–2162. 2. FAO. (2020). Maximum residue limits for pesticides in food and agriculture. Food and Agriculture Organization of the United Nations. 3. Johnson, R. D., & Williams, P. K. (2019). Root rot diseases in cotton: Etiology, distribution, and control strategies. 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