Incidence and distribution of basal rot of onion (Allium cepa L.) in Davanagere, Chitradurga and Chikkamagaluru districts of Karnataka

Introduction

Onion (Allium cepa L.) is an important commercial vegetable crop cultivated extensively for its culinary, nutritional and economic value. Its production is affected by several diseases, among which basal rot is an important soil-borne disease that affects roots and the basal plate of bulbs. Infected plants commonly exhibit the symptoms such as chlorosis, leaf curling, wilting and progressive drying of foliage, while below-ground symptoms include root decay and rotting of the basal portion of the bulb. Fusarium basal rot is widely distributed in onion-growing regions and its incidence varies with environmental conditions, soil characteristics, crop stage, cultivar susceptibility, pathogen inoculum and crop management practices. In India, basal rot has been reported from several onion-growing regions, and Fusarium oxysporum f. sp. cepae has historically been recognized as an important causal pathogen. Anupama et al. (2014) [1] reported basal rot incidence in onion-growing regions of Karnataka (Anupama et al., 2014) [1] , while Koppad et al. (2017) [2] documented the occurrence of basal rot along with other major onion diseases in northern Karnataka (Koppad et al., 2017) [2] . More recently, surveys in other onion-growing regions of India have also demonstrated considerable spatial variation in disease incidence (Muthukumar et al., 2022) [3] . Although previous studies have documented basal rot in Karnataka, updated information on its incidence in the important onion-growing areas of Davanagere, Chitradurga and Chikkamagaluru districts is limited. Therefore, the present investigation was undertaken to assess the incidence and distribution of basal rot of onion in these districts of Karnataka.

Materials and Methods

Survey for incidence of basal rot

A random roving survey was conducted during 2025 in major onion-growing areas of Davanagere, Chitradurga and Chikkamagaluru districts of Karnataka. Different taluks and villages were selected to assess the occurrence and incidence of basal rot. During the survey, onion fields were examined for plants showing characteristic symptoms of basal rot. Diseased plant samples showing typical symptoms were collected in polythene covers and brought to the laboratory for further studies. Various Parameters like district, taluk and village, GPS coordinates, crop stage, disease incidence and other diseases observed were recorded. Disease incidence was calculated according to Wheeler (1969) [4] using the following formula:

𝐷𝐼 (%) = 𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑑𝑖𝑠𝑒𝑎𝑠𝑒𝑑 𝑝𝑙𝑎𝑛𝑡𝑠 𝑇𝑜𝑡𝑎𝑙 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑝𝑙𝑎𝑛𝑡𝑠 𝑜𝑏𝑠𝑒𝑟𝑣𝑒𝑑 × 100

Results

Occurrence and incidence of basal rot

The survey revealed that basal rot occurred in the onion-growing areas of all three districts surveyed, namely Davanagere, Chitradurga and Chikkamagaluru. Disease incidence varied considerably among the surveyed locations and ranged from 20.37 to 43.64 per cent (Table 3). The highest disease incidence was recorded in Arasinagundi village of Jagalur taluk, Davanagere district (43.64 %), whereas the lowest incidence was recorded in Arehalli village of Nyamthi taluk, Davanagere district (20.37 %).

District-wise incidence

Davanagere district recorded the highest mean disease incidence of 31.75 per cent, followed by Chitradurga (26.34 %) and Chikkamagaluru (22.89 %) (Table 1, Figure 1). In Davanagere, Jagalur recorded the highest taluk mean incidence (41.03 %), followed by Nyamthi (28.20 %) and Honnali (26.03 %). In Chitradurga, Hiriyur recorded the highest taluk mean incidence (27.55 %), followed by Chitradurga (26.93 %) and Challakere (24.54 %). In Chikkamagaluru, Kadur recorded the highest taluk mean incidence (23.67 %), followed by Ajjampura (22.11 %) (Table 2).

Location-wise variation

At the village level, Arasinagundi recorded the highest incidence (43.64 %), followed by Bidarakere (41.27 %) and Katigehalli (38.18 %) in Davanagere district. In Chitradurga district, Aimangala recorded the highest incidence (31.27 %), followed by Madakaripura (30.42 %), whereas Obalapura recorded the lowest incidence (22.63 %). In Chikkamagaluru district, Ballikere recorded the highest incidence (25.14 %), followed by Yagati (24.32 %), while Mallenahalli recorded the lowest incidence (20.79 %) (Table 3).

Symptoms observed during the survey

The affected plants generally showed yellowing, curling and wilting of leaves followed by drying of foliage. Below-ground symptoms included basal plate rot and root decay. Affected bulbs showed brown discoloration and in some cases, whitish fungal growth on the diseased tissues.

Discussion

The present survey established the widespread occurrence of basal rot in the surveyed onion-growing regions of Davanagere, Chitradurga and Chikkamagaluru districts of Karnataka. The disease incidence ranged from 20.37 to 43.64 per cent, indicating considerable spatial variation among locations. The highest incidence was recorded at Arasinagundi village of Jagalur taluk, while the lowest was observed at Arehalli village of Nyamthi taluk. The higher mean disease incidence recorded in Davanagere (31.75 %) compared with Chitradurga (26.34 %) and Chikkamagaluru (22.89 %) suggests comparatively greater disease pressure in the surveyed areas of Davanagere. The observed variation may be related to differences in agro-ecological conditions, soil properties, crop stage, cultivar susceptibility, pathogen inoculum potential and crop management practices.

The present findings are broadly comparable with earlier reports from Karnataka. Anupama et al. (2014) [1] reported basal rot incidence in onion-growing areas of Karnataka, demonstrating substantial variation among locations (Anupama et al., 2014) [1] . Koppad et al. (2017) [2] reported basal rot severity ranging from 7.78 to 12.54 per cent in northern Karnataka (Koppad et al., 2017) [2] . The incidence recorded in the present survey was higher than that reported in the latter study, particularly at locations in Davanagere district. Such differences may be associated with differences in survey period, agro-climatic conditions, soil type, crop stage, cultivar and disease-conducive conditions. Muthukumar et al. (2022) [3] reported basal rot incidence ranging from 10.12 to 28.50 per cent in major onion-growing regions of Tamil Nadu (Muthukumar et al., 2022) [3] . The maximum incidence observed in the present study was therefore comparatively higher. Differences among regions may reflect variation in environmental conditions, edaphic factors, cropping systems, host susceptibility and pathogen populations. Recent studies have also demonstrated that the Fusarium species associated with onion basal rot can vary among geographical regions. Bhat et al. (2023) [5] reported Fusarium acutatum and Fusarium falciforme from basal rot-affected onion fields in Karnataka (Bhat et al., 2023) [5] . These findings emphasize the importance of continued field surveillance and pathogen characterization in different onion-growing regions. Breeding for host resistance also remains an important longterm management option for Fusarium basal rot of onion (Cramer, 2000) [6] . The present survey provides updated information on the distribution and incidence of basal rot in three important onion-growing districts of Karnataka.

Conclusion

Basal rot of onion was widely distributed in the surveyed onion-growing areas of Davanagere, Chitradurga and Chikkamagaluru districts of Karnataka, with disease incidence ranging from 20.37 to 43.64 per cent. Davanagere recorded the highest district mean incidence (31.75 %), while Chikkamagaluru recorded the lowest (22.89 %). The considerable variation among locations highlights the need for regular disease surveillance and location-specific integrated disease management. The survey data provide a useful baseline for future epidemiological studies and management programmes for onion basal rot in Karnataka.

Figures

Acknowledgement

AcknowledgmentsThe author is grateful to the Department of Plant Pathology, College of Agriculture, Shivamogga, Keladi Shivappa Nayaka University of Agricultural and Horticultural Sciences, Shivamogga, Karnataka, for providing facilities and support for the study.

References

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7. How to cite this article: Rathod S, Ekabote SD, Navali GV, AN R, Gondi SP. Incidence and distribution of basal rot of onion (Allium cepa L.) in Davanagere, Chitradurga and Chikkamagaluru districts of Karnataka. International Journal of Research in Agronomy. 2026;9(9):1227-1230. doi: https://www.d oi.org/10.33545/2618060X.2026.v9.i9q.6674