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Standardization of challenge inoculation protocols for artificial infection of Fusarium acutatum and Fusarium falciforme causing basal rot of onion

Summary

This research develops standardized methods for infecting onion bulbs with fungal diseases in laboratory settings to test which onion varieties can resist the infection. Two Fusarium fungi species that cause onion basal rot were tested using five different inoculation techniques. The cotton swab method proved most effective and practical for screening large numbers of onion plants. These findings will help farmers and plant breeders develop onion varieties resistant to these economically important diseases.

Background

Fusarium basal rot (FBR) is a economically significant seed and soil-borne disease of onion caused by various Fusarium species including F. acutatum and F. falciforme. The disease causes substantial pre- and post-harvest losses, with yield reductions up to 50% in the field and 30-40% during post-harvest storage. Standardized laboratory inoculation protocols are needed for evaluating pathogen-host interactions and screening for disease resistance.

Objective

The study evaluated and compared five different onion bulb inoculation methods to standardize and optimize artificial infection protocols for F. acutatum and F. falciforme under controlled laboratory conditions. The objective was to develop reliable, reproducible procedures suitable for mass screening of onion genotypes for FBR resistance.

Results

The cotton swab method was most effective, showing 56% rotting for F. acutatum and 92% for F. falciforme by 15 days post-inoculation. F. falciforme demonstrated higher pathogenicity than F. acutatum across all methods, with affected surface areas ranging from 32-70 cm² and 64-81 cm² respectively. Early symptom appearance in F. acutatum (3 days) contrasted with F. falciforme (5 days), though the latter caused greater tissue damage.

Conclusion

The cotton swab method and pinprick with dipping method were identified as the most suitable for artificial FBR infection, being rapid, easy to execute, cost-effective, and producing consistent results. These standardized protocols are recommended for screening onion genotypes for FBR resistance and implementing sustainable management strategies against these pathogens.
  • Published in:Scientific Reports,
  • Study Type:Experimental Study,
  • Source: 10.1038/s41598-025-23382-4; PMID: 41224876
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