Fungicides Linked to Fungal Drug Resistance | 26 Jun 2025

Source: TH

A study reveals that the agricultural fungicide tebuconazole is driving increased resistance in Candida tropicalis (a fungal pathogen) by causing unexpected genetic changes that make the strains resistant to commonly used antifungal drugs like fluconazole and voriconazole.

• Candida tropicalis is responsible for severe fungal infections, with a mortality rate of 55-60%.

Tebuconazole

• About: Tebuconazole is a systemic, broad-spectrum fungicide used widely in agriculture to control fungal diseases in crops like wheat, barley, rice, fruits, vegetables, and turf.
• Working: Tebuconazole, similar to medical antifungals like fluconazole and voriconazole, works by inhibiting ergosterol biosynthesis, essential for fungal cell membrane formation, giving it both preventive and curative properties. 
  • It is widely applied as a seed treatment, soil drench, or foliar spray, offering versatile crop protection. However, its overuse in agriculture has raised concerns due to its role in promoting antifungal resistance.
• Impact of Overuse: Overuse of the fungicide tebuconazole in agriculture promotes cross-resistance in Candida tropicalis by inducing aneuploidy i.e. changes in chromosome number that lead to the overexpression or deletion of resistance-related genes.
  • Strains with altered ploidy grow slower without drugs but survive better when exposed to antifungals.
  • Some strains became haploid (having only one set of chromosomes and the ability to mate), potentially spreading resistance further.
    • Ploidy refers to the number of complete chromosome sets in a cell. Diploid (2n) has two sets (common in human cells), haploid (1n) has one set (seen in sperm and egg), and triploid (3n) has three sets.

Fungicides

• These are crop protection chemicals (pesticides)  used to control the spread of fungal diseases in plants. It includes Chlorothalonil, dithiocarbamates (e.g. mancozeb, maneb, zineb), sulfur derivatives etc.