The Novel Oomycide Oxathiapiprolin Inhibits All Stages in the Asexual Life Cycle of Pseudoperonospora cubensis - Causal Agent of Cucurbit Downy Mildew

Abstract

Oxathiapiprolin is a new oomycide (piperidinyl thiazole isoxazoline class) discovered by DuPont which controls diseases caused by oomycete plant pathogens. It binds in the oxysterol-binding protein domain of Oomycetes. Growth chambers studies with detached leaves and potted plants showed remarkable activity of oxathiapiprolin against Pseudoperonospora cubensis in cucurbits. The compound affected all stages in the asexual life cycle of the pathogen. It inhibited zoospore release, cystospore germination, lesion formation, lesion expansion, sporangiophore development and sporangial production. When applied to the foliage as a preventive spray no lesions developed due to inhibition of zoospore release and cystospore germination, and when applied curatively, at one or two days after inoculation, small restricted lesions developed but no sporulation occurred. When applied later to mature lesions, sporulation was strongly inhibited. Oxathiapiprolin suppressed sporulation of P. cubensis in naturally-infected leaves. It exhibited trans-laminar activity, translocated acropetaly from older to younger leaves, and moved from the root system to the foliage. Seed coating was highly effective in protecting the developed cucumber plants against downy mildew. UV microscopy observations made with cucumber leaves infected with P. cubensis revealed that inhibition of mycelium growth and sporulation induced by oxathiapiprolin was associated with callose encasement of the haustoria.

Oxathiapiprolin, a Novel Chemical Inducer Activates the Plant Disease Resistance

“…Previous research indicated that OX exhibited direct and high inhibition activity against the growth of many oomycete pathogens with a low dose. The target protein of OX was the oxysterol binding protein (OSBP) in oomycetes [33][34][35][36][37]. Besides, OX exhibited both curative and protective activity against pepper Phytophthora blight, and the protective activity was better [37].…”

“…Oxathiapiprolin (OX), a piperidinyl thiazole isoxazoline fungicide, was synthesized by DuPont Company in 2007 [32,33]. OX was developed as an oomycete inhibitor with a high inhibition activity against many oomycetes, including Phytophthora capsici, Phytophthora infestans, Phytophthora sojae, Phytophthora parasitica, Phytophthora nicotianae, Pseudoperonospora cubensis, and Pythium ultimum [34][35][36][37]. Previous study showed that OX could interact with the oxysterol binding protein (OSBP) in oomycetes, which indicated that OSBP might be the target protein of OX [33].…”

Current status of chirality in agrochemicals

“…Oxathiapiprolin (Fig. ), is the first member of a novel class of piperidinyl thiazole isoxazoline fungicides with exceptionally high activity against diseases caused by Oomycete pathogens. Via a novel target for fungicides, it inhibits an oxysterol‐binding protein resulting in excellent preventive, curative and residual efficacy against diseases in grapes, potatoes and vegetables at low use rates …”

Synthesis of 4‐Hetarylisoxazoles from Amino Acid‐Derived Halogenoximes and Push‐Pull Enamines

“…Isoxazole is one of the top 10 % heterocycles frequently used in drug discovery , . Derivatives of this heterocycle are widespread among natural products; they are represented by antirheumatic and antiviral drugs, fungicides, and hypoglycemic agents . Isoxazole‐based sulfonamide antibiotics can be found in the World Health Organization model list of essential medicines…”