<i>Sdh</i>C-I86F Mutation in <i>Phakopsora pachyrhizi</i> Is Stable and Can Be Related to Fitness Penalties
Alexandre Claus, Kelly Simões, Louise L. May De Mio
Abstract
Succinate dehydrogenase inhibitors (SDHIs) fungicides are used to control Asian soybean rust (Phakopsora pachyrhizi), and the SdhC-I86F mutation is related to pathogen resistance. The objective of this study was to determine whether fitness penalties are associated with SDHI resistance (SdhC-I86F mutation) in P. pachyrhizi populations. Moreover, the study investigated whether the SdhC-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 SdhC), except for a wild-type population (WT Sdh C ) found with no SdhC-I86F mutation. The frequencies of the SdhC-I86F mutant populations were stable after 36 generations in the absence of fungicide. However, in the case of the WT Sdh C population, the SdhC-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). SdhC-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 SdhC-I86F mutant populations can be relevant to the management of the disease in the field.