R034-1 is a new member of the piperidinyl thiazole isoxazoline class of fungicides that shows high activity against most plant-pathogenic oomycetes and could effectively inhibit several developmental stages of Phytophthora capsici. Here, the potential resistance risk for R034-1 was evaluated in P. capsici. The baseline sensitivities of 135 isolates to R034-1 showed a unimodal curve, with a mean EC50 value of 0.004 μg/mL. Twelve resistant mutants were generated by fungicide adaptation and displayed lower fitness compared to parental isolates, which suggests that the resistance risk of P. capsici to R034-1 is low. R034-1 and oxathiapiprolin are structurally related, and resistant isolates display cross-resistance to both compounds, suggesting that these fungicides may target the same oxysterol binding protein. Comparison of PcORP1 genes in the resistant mutants and their parental isolates revealed (N767S, N767I, and G700V) amino acid substitutions in the R034-1 resistant mutant. Causality was functionally validated using site-directed mutagenesis of the target gene using the CRISPR/Cas9 system.

Botrytis cinerea is a destructive necrotrophic pathogen that can infect many plant species. The control of gray mold mainly relies on the application of fungicides, and the fungicide fludioxonil is widely used in China. However, the field fungicide resistance of B. cinerea to this compound is largely unknown. In this study, B. cinerea isolates were collected from different districts of Shanghai province in 2015–2017, and their sensitivity to fludioxonil was determined. A total of 65 out of 187 field isolates (34.76%) were found to be resistant to fludioxonil, with 36 (19.25%) showing high resistance and 29 (15.51%) showing moderate resistance. Most of these resistant isolates also showed resistance to iprodione, and some developed resistance to fungicides of other modes of action. AtrB gene expression, an indicator of MDR1 and MDR1h phenotypes, was not dramatically increased in the tested resistant isolates. Biological characteristics and osmotic sensitivity investigations showed that the fitness of resistant isolates was lower than that of sensitive ones. To investigate the molecular resistance mechanisms of B. cinerea to fludioxonil, the Bos1 amino acid sequences were compared between resistant and sensitive isolates. Resistant isolates revealed either no amino acid variations or the mutations I365S, I365N, Q369P/N373S, and N373S.

In plant-pathogen interaction systems, plant metabolism is usually agitated in the early stages of infection and much before visible symptoms appear. To identify the latent infection of strawberry by Botrytis cinerea by metabolome profiling, a metabolomics method based on gas chromatography and mass spectrometry was applied to identify the affected metabolites and discriminate diseased plants from healthy ones. An orthogonal partial least squares (OPLS) score plot showed that the metabolic profiling well separated B. cinerea -infected strawberry plants at 2, 5, and 7 days after infection from non-infected healthy plants. Combined analysis of variance (ANOVA) and OPLS analysis revealed candidate biomarkers of plant resistance and of infection and expansion of the pathogen in the plants. Among them, hexadecanoic acid, octadecanoic acid, sucrose, β-lyxopyranose, melibiose, and 1,1,4a-Trimethyl-5,6-dimethylenedecahydronaphthalene were closely related to the early stage of disease development when symptoms were not visible. A discrimination method that could distinguish Botrytis gray mold diseased strawberry plants from healthy ones was established based on the partial least squares discriminant analysis (PLS-DA) model with a correct recognition accuracy of 100%. This research offers a good application of metabolome profiling for early diagnosis of plant disease and interaction mechanism exploration.

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BACKGROUND Coating seed with pesticides is an effective way to control plant pests, however, factory‐based coating processes may carry a potential risk to operational workers of chemical exposure. To study the risk, carbofuran and tebuconazole were used to coat corn seed and their subsequent distribution on the bodies of workers was measured at manufacturers XFS and LS (Shanxi, China). Clothing was collected from workers during operations and analyzed using high‐performance liquid chromatography. RESULTS At XFS, dermal exposure to carbofuran was 4.83, 3.31 and 1.48 mg kg−1, and exposure to tebuconazole was 6.88, 5.16 and 1.72 mg kg−1 for coating, packing and transport workers, respectively. At LS, dermal exposure to carbofuran was 2.32, 0.46 and 0.55 mg kg−1, and exposure to tebuconazole was 1.69, 0.46 and 0.70 mg kg−1, for coating, packing and transport workers, respectively. The level of pesticide exposure was significantly higher for seed‐coating workers than for packing and transport workers. The main area of exposure was the hands for all workers and the lower limbs for packers; exposure was relatively uniform for pesticide handlers. Occupational risk was assessed based on margin of exposure (MOE). In seed‐coating, the MOE was greater than 100 for tebuconazole, indicating no potential risk, but ranged from 0.25 to 2.88 for carbofuran, indicating the risk of a health impact. CONCLUSION The level of exposure varied depending on type of operation undertaken and body parts of workers' body, but the risk of a health impact was highly associated with pesticide toxicity. This provides a guideline for workers in pesticide manufacturing to ensure safe operation of the seed‐coating process. © 2021 Society of Chemical Industry

Guvermectin is a recently discovered microbial N9-glucoside cytokinin compound extracted from Streptomyces sanjiangensis NEAU6. Although some research has reported that N9-glucoside cytokinin compounds do not have the activity of cytokinin, it has been noted that guvermectin can promote growth and antifungal activity in Arabidopsis. Maize is an important food crop in the world and exploring the effect of guvermectin on this crop could help its cultivation in regions with adverse environmental conditions such as a high temperature. Here, we investigated the effects of guvermectin seed soaking treatment on the growth of maize at the seedlings stage and its yield attributes with different temperature stresses. The maize (cv. Zhengdan 958) with guvermectin seed soaking treatment were in two systems: paper roll culture and field conditions. Guvermectin seed soaking treated plants had increased plant height, root length, and mesocotyl length at the seedlings stage, and spike weight at maturity in the field. But only root length was increased at the paper roll culture by guvermectin seed soaking treatment. Guvermectin seed soaking treatment reduced the adverse effects on maize seedling when grow at a high temperature. Further experiments showed that, in high temperature conditions, guvermectin treatment promoted the accumulation of heat shock protein (HSP) 17.0, HSP 17.4 and HSP 17.9 in maize roots. Comparative transcriptomic profiling showed there were 33 common differentially expressed genes (DEGs) in guvermectin treated plants under high temperature and room temperature conditions. The DEGs suggested that guvermectin treatment led to the differential modulation of several transcripts mainly related with plant defense, stress response, and terpenoid biosynthesis. Taken together, these results suggested that the guvermectin treatment promoted the growth and tolerance of high temperature stresses, possibly by activation of related pathways. These results show that guvermectin is a novel plant growth regulator and could be developed as an application to maize seeds to promote growth in high temperature environments.

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Oomycetes, particularly those from the genus Phytophthora, are significant threats to global food security and natural ecosystems. Oxathiapiprolin (OXA) is an effective oomycete fungicide that targets an oxysterol binding protein (OSBP), while the binding mechanism of OXA is still unclear, which limits the pesticide design, induced by the low sequence identity of Phytophthora and template models. Herein, we generated the OSBP model of the well-reported Phytophthora capsici using AlphaFold 2 and studied the binding mechanism of OXA. Based on it, a series of OXA analogues were designed. Then, compound 2l, the most potent candidate, was successfully designed and synthesized, showing a control efficiency comparable to that of OXA. Moreover, field trial experiments showed that 2l exhibited nearly the same activity (72.4%) as OXA against cucumber downy mildew at 25 g/ha. The present work indicated that 2l could be used as a leading compound for the discovery of new OSBP fungicides.