Spatial Distribution and Seasonal Variability of Seed-borne Fungal Pathogens of Soybean in Relation to Seed Health Parameters in Telangana, India

Abstract

Background: Seed-borne fungi are important constraints to soybean production as they adversely affect seed quality, germination and field establishment, and also serve as primary inoculum for several diseases.  Aims: The study aims to assess the seed health status of soybean seed lots collected from farmers’ fields in major soybean-growing mandals of Telangana and compare the efficiency of the Standard Blotter Method and the Agar Plate Method in detecting major seed-borne fungi, and analyse mandal- and district-wise patterns in pathogen severity and frequency to derive implications for seed health management in soybean. Methodology: A two-year seed health survey was conducted during Kharif 2023 and Kharif 2024 in major soybean-growing mandals of five districts of Telangana, namely Adilabad, Nizamabad, Nirmal, Kamareddy and Sangareddy. Farmers’ seed samples were collected at harvest and evaluated by the Standard Blotter Method and the Agar Plate Method for the detection of major seed-borne fungi, viz., Colletotrichum truncatum, Macrophomina phaseolina, Alternaria spp., Fusarium spp. and Aspergillus spp. Results: Marked variation in seed infection was observed among mandals, districts, seasons and detection methods. Across both years, Aspergillus spp. and M. phaseolina were dominant, with higher recovery on the Agar Plate Method, indicating their strong saprophytic and storage-associated nature. The Standard Blotter Method was more efficient in detecting field-borne fungi such as C. truncatum and Alternaria spp., particularly in anthracnose hotspot mandals like Rajampet, Jainath, Bodhan and Sadasivanagar. District-wise analysis consistently identified Nizamabad and Adilabad as the most heavily contaminated, whereas Nirmal and Sangareddy generally exhibited moderate to lower infection. Year-wise comparison showed a reduction in C. truncatum severity in Kharif 2024 as compared to Kharif 2023, probably due to drier pre-harvest weather, while M. phaseolina and Aspergillus spp. continued to dominate the seed mycoflora. Analysis of variance revealed highly significant effects of pathogen, location and their interaction, indicating that both agro-climatic factors and pathogen biology determine infection patterns. Conclusion: The results confirm the complementary value of the Standard Blotter Method and the Agar Plate Method for seed health diagnosis and highlight the need for region-specific seed management strategies, emphasising field sanitation, timely harvest, proper drying and improved storage, to reduce seed-borne inoculum in soybean-growing areas of Telangana.