Characterization of the Chilli Viral Complex in Major Chilli-growing Regions of Telangana, India

Abstract

Aims: The present investigation was undertaken to characterise the chilli viral complex prevalent in the major chilli-growing regions of Telangana through symptomatological, biological, serological, molecular and electron microscopic analyses and to identify the major viruses associated with the disease to improve diagnosis and disease management strategies. Study Design: Field survey-based investigation followed by laboratory diagnosis using infectivity assays, serological detection, molecular characterisation and transmission electron microscopy. Place and Duration of Study: Department of Plant Pathology, College of Agriculture, Professor Jayashankar Telangana Agricultural University, Rajendranagar, Hyderabad, India, and major chilli-growing districts of Telangana during Rabi 2019–20 and 2020–21. Methodology: Extensive field surveys were conducted in six major chilli-growing districts of Telangana to record disease incidence and symptom variability. Virus-infected samples exhibiting characteristic symptoms were collected and subjected to infectivity assays through sap inoculation onto the susceptible chilli cultivar 'Sindhur'. Serological detection of Cucumber mosaic virus (CMV) was performed using DAC-ELISA, while molecular identification of chilli leaf curl virus was carried out through PCR amplification using Tomato leaf curl virus-specific primers. Purified virus preparations were further examined using transmission electron microscopy to confirm virus morphology. Host range studies and weed reservoir investigations were also undertaken to identify alternate hosts contributing to disease epidemiology. Results: Field surveys revealed that the chilli viral complex was characterised by diverse symptoms, including upward leaf curling, mosaic mottling, vein clearing, puckering, shoe-stringing, vein banding and severe stunting, with symptom severity varying among cultivars and locations. Infectivity assays grouped the virus isolates into two major categories corresponding to Cucumber mosaic virus and chilli leaf curl virus. DAC-ELISA confirmed CMV infection in a substantial proportion of symptomatic samples, particularly those exhibiting shoe-string and mosaic symptoms. PCR amplification using ToLCV-specific primers generated the expected approximately 1000 bp amplicon, confirming the association of Begomovirus with chilli leaf curl disease. Electron microscopic examination revealed spherical particles measuring approximately 28–30 nm, typical of CMV and twinned icosahedral particles characteristic of begomoviruses. Several weed species and cultivated hosts were identified as important reservoirs of inoculum, indicating their significant role in virus survival and dissemination. Conclusion: The study established that the chilli viral complex prevailing in Telangana is predominantly associated with Cucumber mosaic virus and chilli leaf curl virus. Accurate diagnosis requires the integration of symptomatological observations with serological, molecular and electron microscopic techniques. Identification of alternate weed hosts and susceptible crop species provides valuable information for understanding disease epidemiology and supports the development of effective integrated disease management strategies for sustainable chilli production.