Azoxystrobin acts as an inhibitor of electron transport by binding to the Qo center of cytochrome b (cyt b). Resistance to azoxystrobin was usually caused by the point mutation of cyt b gene or by the induction of alternative respiration. Oxygen consumption test for mycelia of Colletotrichum capsici showed that azoxystrobin inhibited mycelial respiration within 12 h; however, as time went on, the respiration of the mycelia recovered when the mycelia were treated with azoxystrobin and salicylhydroxamic acid (SHAM, a known inhibitor of alternative respiration), and the oxygen consumption of the mycelia could not be inhibited. Meanwhile, cytochrome b (cyt b) gene expression increased with the recovery of mycelial respiration. The increased cyt b gene expression might play a role in the development of resistance to azoxystrobin in C. capsici.
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