Sensitivity of Colletotrichum truncatum to Four Fungicides and Characterization of Thiabendazole-Resistant Isolates

Abstract

Anthracnose, caused by Colletotrichum truncatum (syn. C. capsici), has become a common disease of tropical crops, severely affecting the quantity and quality of fruit and seed and, therefore, reducing their market value. For years, chemical control has been extensively used for managing this disease. However, the appearance of isolates that are resistant to the most commonly employed fungicides is increasingly widespread. Twenty C. truncatum isolates from pepper, papaya, and physic nut were tested in vitro against four fungicides to determine their sensitivity. All evaluated isolates were resistant to azoxystrobin and thiabendazole and susceptible to cyprodinil + fludioxonil and mancozeb. To determine the molecular mechanism conferring thiabendazole resistance, the TUB-2 gene was characterized, revealing a glutamic acid to alanine substitution at position 198 in 6 of the 20 isolates that were tested. This work confirms the emergence of benzimidazole-based fungicide resistance in C. truncatum populations and highlights the need for monitoring fungicide sensitivity as an essential activity for the development of effective control schemes.