Sdh C-I86F Mutation in Phakopsora pachyrhizi Is Stable and Can Be Related to Fitness Penalties.

Succinate dehydrogenase inhibitors (SDHIs) fungicides are used to control Asian soybean rust ( Phakopsora pachyrhizi ), and the Sdh C-I86F mutation is related to pathogen resistance. The objective of this study was to determine whether fitness penalties are associated with SDHI resistance ( Sdh C-I86F mutation) in P. pachyrhizi populations. Moreover, the study investigated whether the Sdh C-I86F mutation remained stable after the fungus propagation both in the absence and presence of fungicide. The populations used in this study presented mutations for all genes analyzed ( Cyp51 , Cytb , and Sdh C), except for a wild-type population (WT _{Sdh C} ) found with no Sdh C-I86F mutation. The frequencies of the Sdh C-I86F mutant populations were stable after 36 generations in the absence of fungicide. However, in the case of the WT _{Sdh C} population, the Sdh C-I86F mutation was further detected after one generation of the fungus in the presence of the SDHI fungicide, according to the results of a detached leaf assay. Three tests were performed to evaluate fitness components and sensitivity to fungicides (half maximal effective concentration). Sdh C-I86F mutant populations were more sensitive to osmotic and oxidative stress than the WT _{Sdh C} population; however, the sensitivity to ultraviolet radiation was similar for both populations. All mutated populations were less sensitive than the WT _{Sdh C} when using SDHI (azoxystrobin + benzovindiflupyr), but more sensitive to mancozeb. The presence of fitness penalties, the mutation stability, and the sensitivity to mancozeb presented by the Sdh C-I86F mutant populations can be relevant to the management of the disease in the field.