Three point‐mutations in cytochrome b confer resistance to trifloxystrobin in Magnaporthe oryzae

Abstract

BACKGROUND: Rice blast, caused by Magnaporthe oryzae, is the most devastating disease in rice. Recently, trifloxystrobin was registered for the control of M. oryzae in China. The resistance profile and mechanism of M. oryzae to trifloxystrobin were investigated in the present study, providing important data for the recommended use of trifloxystrobin. RESULTS: The baseline sensitivity was established at a half maximal effective concentration (EC 50) of 0.024 ∼g mL −1. Nine stable trifloxystrobin-resistant mutants were generated with EC 50 values ranging from 12.75 to 171.49 ∼g mL −1. The mutants exhibited strong adaptive traits in sporulation, conidial germination, and pathogenicity. Positive cross-resistance was only observed between trifloxystrobin and azoxystrobin, but not between trifloxystrobin and carbendazim, isoprothiolane, prochloraz, or chlorothalonil. The point mutation G143S in cytochrome b (cyt b) protein was found in eight high-resistance mutants with resistant factor ranging from 2295.16 to 13 200.00; and the double mutation G137R/M296V only occurred in Mg117-1 with resistance factor ≈ 900. The G143S mutation weakened hydrogen bond interactions, and G137R/M296V changed the conformation of trifloxystrobin in the cyt b binding pocket. A molecular detection method was established for the rapid detection of G143S mutants in M. oryzae. CONCLUSION: The resistance risk of M. oryzae to trifloxystrobin could be moderate to high. Two genotypes with three pointmutations G143S, G137R, and M296V conferred resistance to trifloxystrobin in M. oryzae.

Resistance Risk and Resistance-Related Point Mutations in Target Protein Cyt b of the Quinone Inside Inhibitor Amisulbrom in Phytophthora litchii

“…Fungicides molecularly bind to target proteins to form a specific complex and is a process that requires high specificity and affinity interactions . When amino acid changes are introduced to the target protein, the recognition and binding efficiencies may decrease between a fungicide and target protein, and resistance may develop. − The binding energy for amisulbrom in wild-type PlCyt b is −5.93 kcal/mol, and, when the H15Y change was introduced, the binding energy reduced to −5.45 kcal/mol. Furthermore, the G30E + F220L linkage mutation was found in the amisulbrom-resistant mutants, but the contribution of the two amino acid substitutions to resistance is unknown.…”

“…However, the Cyt b gene located in mitochondrial genome and the mitochondrial gene edit system had not been developed in plant pathogens. Until now, the molecular docking and enzyme activity assay are the most frequently used methods in confirmation of the relationship of the point mutations in Cyt b and QoI, QiI, or QioI fungicides’ resistance. ,, …”

Characterization of pyraclostrobin‐resistant Magnaporthe oryzae

“…oryzae and C . Beticola mutants (Avila‐Adame & Köller, 2003; Malandrakis et al, 2011; Miao et al, 2020).…”

“…Mechanisms of QoI resistance have been generally linked to mutations in the cytb gene, specifically in the amino acid mutation at positions 129, 137, and 143. The G143A and F129L are the most commonly found mutations conferring high or moderate levels of resistance to the QoI fungicides (Kim et al, 2003; Chen, 2015; Forcelini et al, 2018; Hu et al, 2015; Keevan et al, 2020; Miao et al, 2020). In some mutants, glycine at position 137 is replaced by arginine (G137R) or leucine at position 275 is replaced by serine or phenylalanine (L275S/F) in the cytb gene.…”

“…In some mutants, glycine at position 137 is replaced by arginine (G137R) or leucine at position 275 is replaced by serine or phenylalanine (L275S/F) in the cytb gene. These mutations, however, confer low or moderate levels of resistance to QoI fungicides (Miao et al, 2020; Sierotzki et al, 2007; Wang, 2018).…”