Mutations confer resistance to carbendazim in Neopestalotiopsis clavispora

Researchers have identified carbendazim resistance in Neopestalotiopsis clavispora. The survey evaluated 85 fungal isolates from the Pestalotiopsis group collected from crops in Jiangsu province, China. Seventeen showed resistance, a frequency equivalent to 20%.

Resistant isolates showed a minimum inhibitory concentration greater than 100 micrograms per milliliter (doi 10.1016/j.aac.2026.09.001). In subsequent evaluations, six isolates of Neopestalotiopsis clavispora reached high to extremely high resistance levels. The minimum inhibitory concentration ranged from 200 to more than 1.000 micrograms per milliliter. The sensitive isolate showed a value of 0,2 micrograms per milliliter.

Molecular analysis

Molecular analysis identified three amino acid substitutions in beta-2-tubulin: E197K, E197A, and F199Y. Gene substitution experiments confirmed the ability of each mutation, individually, to confer resistance to carbendazim.

Molecular modeling also indicated a reduction in the affinity between the fungicide and the mutant proteins. The calculated affinity went from -7,6 kilocalories per mole in the original protein to values ​​between -6,7 and -6,8 kilocalories per mole in the mutant forms.

Resistant isolates did not show significant loss of sporulation capacity or pathogenicity. Mycelial growth showed punctual differences between isolates. The assays also did not detect significant cross-resistance to fenamacryl, prochloraz, fludioxonil, or tebuconazole. The researchers highlight the need for management strategies focused on resistance and the use of fungicides with different mechanisms of action.

The use of carbendazim is prohibited in Brazil (Anvisa RDC No. 739, of August 8, 2022).