Sensitivity of Different Developmental Stages and Resistance Risk Assessment of Phytophthora capsici to Fluopicolide in China

Abstract

Sensitivities of Phytophthora capsici to fluopicolide were investigated in vitro, with results showing that fluopicolide had strong inhibitory activities on each development stage of P. capsici, in particular on the motility of the zoospore. The potential resistance risk for fluopicolide in P. capsici was evaluated. The baseline sensitivities to fluopicolide of 146 isolates obtained from 28 provinces in China were initially determined, and the 50% inhibition of mycelial growth (EC 50) distribution was a unimodal curve with a mean of 0.17 µg/ml. A series of fluopicolide-resistant mutants of P. capsici were obtained by fungicide adaptation, and their biological traits were determined. Most of the resistant mutants showed similar favorable fitness in mycelial growth, sporangium and zoospore production, cystospore germination, and pathogenicity compared with their sensitive parents, with few exceptions. Additionally, the cross-resistance result indicated that the sensitivity of fluopicolide did not correlate with other oomycete fungicides, apart from fluopimomide (LH-2010A). These results suggest a moderate to high resistance risk of P. capsici to fluopicolide in China.

A Patched-Like Protein PsPTL Is Not Essential for the Growth and Response to Various Stresses in Phytophthora sojae

“…Oomycetes are filamentous microorganisms that are evolutionarily distant from fungi, with a closer phylogenetic relationship to brown algae and diatoms (Thines and Kamoun, 2010;Wu et al, 2020). Phytophthora sojae is one of the top 10 oomycete pathogens in molecular plant pathology and has been developed as a model oomycete (Tyler, 2007;Kamoun et al, 2015;Zhang et al, 2020).…”

Activity and Resistance Assessment of a New OSBP Inhibitor, R034-1, in Phytophthora capsici and the Detection of Point Mutations in PcORP1 that Confer Resistance

“…Pepper seedlings were cultivated to the four-true-leaf stage. 13,14 In Vitro Activity of R034-1 and R031-1 against Plant-Pathogenic Oomycetes and Magnaporthe oryzae. P. capsici, P. sojae, P. nicotianae, P. litchi, P. ultimum, P. delicense, P. aphanidermatum, and M. oryzae were cultured in the potato dextrose broth (PDB) medium, and P. sojae was cultured in the V8 juice liquid medium for 72−96 h at 25 °C.…”

“…Additionally, P. capsici isolates were cultured on the V8 juice agar medium for sporangial production. , The P. capsici isolates HNJZ10-E and LP3-M included in this study are oxathiapiprolin-resistant mutants obtained previously (resistance factor > 1000) …”

“…13 Systematic and comprehensive resistance risk assessment of new fungicides is particularly important and has been listed as a necessary regulatory process for product approval in China since 2012 (NY/T1859.2-2012). 14,15 This process mainly includes the following aspects: the establishment of the baseline sensitivity of a large number of pathogens, determination of the survival fitness for stable resistant mutants, and the measurement of cross-resistance with other fungicides. 13,14 Oxathiapiprolin was discovered and developed by Du Pont in 2007 and then registered in China in 2016.…”

“…14,15 This process mainly includes the following aspects: the establishment of the baseline sensitivity of a large number of pathogens, determination of the survival fitness for stable resistant mutants, and the measurement of cross-resistance with other fungicides. 13,14 Oxathiapiprolin was discovered and developed by Du Pont in 2007 and then registered in China in 2016. 16 It is the first member of the piperidinyl thiazole isoxazoline class of fungicides and has been shown to have excellent activity against various plant pathogenic oomycetes, such as P. capsici, P. nicotianae, and Pseudoperonospora cubensis.…”