Survey of prothioconazole sensitivity in Fusarium pseudograminearum isolates from Henan Province, China, and characterization of resistant laboratory mutants.

BACKGROUND: Fusarium crown rot (FCR) is one of the most significant diseases limiting crop production in the Huanghuai wheat-growing region of China. Prothioconazole, a triazole sterol 14α-demethylation inhibitor (DMI) fungicide developed by the Bayer Crop Protection Company, is mainly registered for the prevention and control of wheat powdery mildew and stripe rust (China Pesticide Information Network). It is known to exhibit high activity against F. pseudograminearum, but further research, particularly regarding the potential for fungicide resistance, is required before it can be registered for the control of FCR in China. RESULTS: The current study found that the baseline sensitivity of 67 field isolates of F. pseudograminearum collected between 2019 and 2021 ranged between 0.016-2.974 µg/mL, with an average EC50 value of 1.191 ± 0.720 µg/mL (mean ± SD). Although none of the field isolates exhibited signs of resistance, three highly resistant mutants were produced by repeated exposure to prothioconazole under laboratory conditions. All of the mutants were found to exhibit significantly reduced growth rates on potato dextrose agar (PDA), as well as reduced levels of sporulation, which indicated that there was a fitness cost associated with the resistance. However, inoculation of wounded wheat coleoptiles revealed that the pathogenicity of the resistant mutants was little affected or actually increased. Molecular analysis of the genes corresponding to the prothioconazole target protein, FpCYP51 (FpCYP51A, FpCYP51B, and FpCYP51C), indicated that the resistant mutants contained three conserved substitutions (M63I, A205S, and I246V) that were present in the FpCYP51C sequence of all three mutants, as well as several non-conserved substations in their FpCYP51A and FpCYP51B sequences. Expression analysis revealed that the presence of prothioconazole (0.1 µg/mL) generally resulted in reduced expression of the three FpCYP51 genes, but that the three mutants exhibited more complex patterns of expression that differed in comparison to their parental isolates. The study found no evidence of cross-resistance between prothioconazole and any of the fungicides tested including three DMI fungicides tebuconazole, prochloraz, and flutriafol. CONCLUSIONS: Taken together these results not only provide new insight into the resistant mechanism and biological characteristics associated with prothioconazole resistance in F. pseudograminearum, but also strong evidence that prothioconazole could provide effective and sustained control of FCR, especially when applied in combination with other fungicides.

Integrative physiological, critical plant endogenous hormones, and transcriptomic analyses reveal the difenoconazole stress response mechanism in wheat (Triticum aestivum L.).

Difenoconazole (DFN) is widely utilized as a fungicide in wheat production. However, its accumulation in plant tissues has a profound impact on the physiological functions of wheat plants, thus severely threatening wheat growth and even jeopardizing human health. This study aims to comprehensively analyze the dynamic dissipation patterns of DFN, along with an investigation into the physiological, hormonal, and transcriptomic responses of wheat seedlings exposed to DFN. The results demonstrated that exposure of wheat roots to DFN (10 mg/kg in soil) led to a significant accumulation of DFN in wheat plants, with the DFN content in roots being notably higher than that in leaves. Accumulating DFN triggered an increase in reactive oxygen species content, malonaldehyde content, and antioxidant enzyme activities, while concurrently inhibiting photosynthesis. Transcriptome analysis further revealed that the number of differentially expressed genes was greater in roots compared with leaves under DFN stress. Key genes in roots and leaves that exhibited a positive response to DFN-induced stress were identified through weighted gene co-expression network analysis. Metabolic pathway analysis indicated that these key genes mainly encode proteins involved in glutathione metabolism, plant hormone signaling, amino acid metabolism, and detoxification/defense pathways. Further results indicated that abscisic acid and salicylic acid play vital roles in the detoxification of leaf and root DFN, respectively. In brief, the abovementioned findings contribute to a deeper understanding of the detrimental effects of DFN on wheat seedlings, while shedding light on the molecular mechanisms underlying the responses of wheat root and leaves to DFN exposure.

Physiological mechanism of sodium salicylate and folcisteine on alleviating salt stress in wheat seedlings.

Soil salinization substantially hampers the growth and development of wheat, potentially leading to plant death in severe cases, thus reducing grain yield and quality. This phenomenon poses a significant threat to food security in China. We investigated the effects of two exogenous plant growth regulators, sodium salicylate and folcisteine, on the wheat physiology and key characteristics under salt stress using hydroponics method. The results indicated that both regulators effectively mitigated the growth inhibition of wheat under salt stress. We assessed morphological and physiological indexes, including antioxidant enzyme activities (superoxide dismutase [SOD], catalase [CAT], peroxidase [POD]) and malondialdehyde (MDA) concentration in wheat after foliar application of sodium salicylate and folcisteine under salt stress. The findings revealed that sodium salicylate was more effective than folcisteine. However, folcisteine showed superior performance in reducing hydrogen peroxide (H2O2) content and superoxide anion (O2-) level compared to sodium salicylate. Simultaneously, Concurrent application of both regulators synergistically enhanced their efficacy, yielding the most favorable outcomes. In addition, this study noted that while the initial effects of these regulators were not pronounced, their sustained application significantly improved wheat growth in stressful condition and alleviated the detrimental impacts of salt stress. This approach could effectively guarantee the food security and production in China.

Exploring the Potential Mechanism of Prothioconazole Resistance in Fusarium graminearum in China.

The Fusarium head blight (FHB) caused by Fusarium graminearum is one of the most important diseases threatening wheat production in China. However, the triazole sterol 14α-demethylation inhibitor (DMI), prothioconazole, is known to exhibit high activity against F. graminearum. The current study indicated that three highly resistant laboratory mutants exhibited significantly (p < 0.05) altered growth and sporulation, although contrary to expectation, only one of the mutants exhibited reduced growth and sporulation, while the other two exhibited significant (p < 0.05) increases. Despite this, pathogenicity tests revealed that all of the mutants exhibited significantly (p < 0.05) reduced pathogenicity, indicating a substantial cost to fitness. Sequence analysis of the prothioconazole target protein, CYP51, of which F. graminearum has three homologues (FgCYP51A, FgCYP51B, and FgCYP51C), identified three mutations in the FgCYP51B sequence with a high likelihood of being associated with the observed resistance, as well as another three mutations in the FgCYP51B sequence, and two in the FgCYP51A sequence that are worthy of further investigation. Two of the prothioconazole-resistant mutants were also found to have several amino acid substitutions in their FgCYP51C sequences, and it was interesting to note that these two mutants exhibited significantly (p < 0.05) reduced pathogenicity compared to the other mutant. Expression analysis revealed that prothioconazole treatment (0.1 µg/mL) resulted in altered expression of all the FgCYP51 target genes, and that expression was also altered in the prothioconazole-resistant mutants compared to their wild-type parental isolates. Meanwhile, no evidence was found of any cross-resistance between prothioconazole and other commonly used fungicides, including carbendazim, pyraclostrobin, and fluazinam, as well as the triazole tebuconazole and the imidazole DMI prochloraz. Taken together, these results not only provide new insight into potential resistance mechanism in F. graminearum, and the biological characteristics associated with them, but also convincing evidence that prothioconazole can offer effective control of FHB.

Physcion and chitosan-Oligosaccharide (COS) synergistically improve the yield by enhancing photosynthetic efficiency and resilience in wheat (Triticum aestivum L.).

As progressively increasing food safety concerns, diversified plant diseases and abiotic stresses, environmental-friendly bio-pesticides and bio-stimulants combinations may are likely to serve as a vital means of safeguarding green and sustainable food production. Accordingly, in this study, pot and field trials were performed to examine the application potential of the combination of physcion and chitosan-Oligosaccharide (COS) in wheat production. Wheat seeds were coated with physcion and COS and the effects exerted by them on morphology, physiology and yield of the wheat were investigated. As indicated by the results, the combination of physcion and COS not only did not inhibit the growth of wheat seedlings, but also synergistically increased root vigor and photosynthetic pigment content. Simultaneously, the lignin content in the roots and leaves was increased significantly. Moreover, the result confirmed that the combination of both substances reduced the MDA content, which was correlated with the up-regulation of the transcript expression level of antioxidant enzyme genes and the resulting increased enzyme activity. Furthermore, this combination synergistically increased the net photosynthetic rate (Pn) of the flag leaves and ultimately contributed to the increase in yield. Notably, the above-mentioned desirable cooperative effect was not limited by cultivars and cultivation methods. The conclusion of this study suggested that the combination of physcion and COS synergistically improved the photosynthetic rate and resilience in wheat, such that high wheat yields can be more significantly maintained, and future food security can be more effectively ensured.

Smart, degradable, and eco-friendly carboxymethyl cellulose-CaII hydrogel-like networks gated MIL-101(FeIII) nanoherbicides for paraquat delivery.

Nanopesticides have been selected as one of the top 10 chemical innovations for enhancing the efficacy and safety of agrochemicals. Herein, smart, degradable, and eco-friendly metal-organic framework MIL-101(FeIII) nanoherbicides coated with carboxymethyl cellulose-CaII (CMC-CaII) cross-linking hydrogel-like networks are synthesized via a simple strategy. The coating of the CMC-CaII hydrogel-like gatekeepers is oriented by the coordination unsaturated FeIII clusters on the surfaces of the MIL-101(FeIII) nanocarriers to form a dense film network to prevent paraquat (PQ) leakage. Based on the stimuli factors (acid/basic pH, GSH, phosphates, and EDTA) of physiological and natural environments of target plants, the nanoherbicides are combined with five stimuli-responsive properties to attain the various controlled release of packaged PQ by the disassembly of the gatekeepers and/or the degradation of the MOF skeleton structure. More importantly, based on the stimuli-responsive controlled release mechanisms, the eco-friendly nanocarriers are ultimately degraded against bioaccumulation in plants or soil. The coating of natural CMC could promote the spreading of PQ owing to improvement of wettability for aqueous droplets of nanoherbicides on hydrophobic foliage. The PQ trapped in nanocarriers can effectively prevent PQ degradation, which showed that cumulative degradation rate is ca. 2.6 times lower than that of technical PQ under UV irradiation. The prepared nanoherbicides loaded with PQ show good control efficacy against weeds by controlling the release of PQ; good safety on seed germination (germination rate 97.32-99.67 %), seedling emergence (emergence rate 95.53-99.67 %), and are beneficial for the growth of wheat seedling (increase rate of plant height 1.89-6.97 % and 0.54-5.67 % after 7 and 15 days of seedling emergence, respectively) in the greenhouse; good biosafety for honeybees (Apis mellifera L.), which shows that lethal rates were 2.04 and 2.55 times lower than technical PQ for incubation 24 and 48 h, respectively. The nanoherbicides have potential applications in the field for PQ green agriculture.

Chitosan oligosaccharide alleviates the growth inhibition caused by physcion and synergistically enhances resilience in maize seedlings.

The use of biopesticides has gradually become essential to ensure food security and sustainable agricultural production. Nevertheless, the use of single biopesticides is frequently suboptimal in agricultural production given the diversity of biotic and abiotic stresses. The present study investigated the effects of two biopesticides, physcion and chitosan-oligosaccharide (COS), alone and in combination, on growth regulation and antioxidant potential of maize seedlings by seed coating. As suggested from the results, physcion significantly inhibited the growth of the shoots of maize seedlings due to the elevated respiration rate. However, COS significantly reduced the growth inhibition induced by physcion in maize seedlings by lowering the respiration rate and increasing the content of photosynthetic pigments and root vigor, which accounted for lower consumption of photosynthesis products, a higher photosynthetic rate and a greater nutrient absorption rate. Thus, an improved growth was identified. As indicated from the in-depth research, the application of physcion and COS combination is more effective in down-regulated the malondialdehyde (MDA) content by facilitating the activities of the antioxidative enzymes (i.e., superoxide dismutase (SOD), catalase (CAT) and guaiacol peroxidase (G-POD)). Such results indicated that the combined use of physcion and COS neither affected the normal growth of maize seedlings, but also synergistically improved the antioxidant potential of the maize plants, resulting in plants with high stress resistance. Thus, the combined use of physcion and COS by seed coating in maize production has great potential to ensure yield and sustainable production of maize.

Mechanism of Pydiflumetofen Resistance in Fusarium graminearum in China.

Fusarium head blight (FHB), which is primarily caused by Fusarium graminearum, is a widespread and devastating disease of wheat. In the absence of resistant varieties, the control of FHB relies heavily on the application of fungicides, and the new generation SDHI fungicide, pydiflumetofen, has recently been registered in China for the control of FHB in wheat. The current study explored three genetically stable, highly resistant laboratory mutants (S2-4-2R, S27-3R, and S28-2R, with EC50 values of 25.10, 28.57, and 19.22 µg/mL, respectively) to investigate the potential risks associated with pydiflumetofen resistance. Although the mycelial growth of the mutants differed little compared to their parental isolates, the study found that the resistant mutants exhibited significantly reduced (p < 0.05) levels of sporulation and pathogenicity, which suggests a significant fitness cost associated with pydiflumetofen resistance in F. graminearum. Sequence analysis of the Sdh target protein identified numerous amino acid substitutions in the predicted sequences of the four subunits: FgSdhA, FgSdhB, FgSdhC, and FgSdhD. Indeed, the mutants were found to have a series of substitution in multiple subunits such that all three exhibited five identical changes, including Y182F in the FgSdhA subunit; H53Q, C90S, and A94V in FgSdhB; and S31F in FgSdhC. In addition, gene expression analysis revealed that all of the FgSdh genes had significantly altered expression (p < 0.05), particularly FgSdhA and FgdhC, which exhibited remarkably low levels of expression. However, the study found no evidence of cross-resistance between pydiflumetofen and tebuconazole, fludioxonil, prochloraz, fluazinam, carbendazim, pyraclostrobin, or difenoconazole, which indicates that these fungicides, either in rotation or combination with pydiflumetofen, could mitigate the risk of resistance emerging and provide ongoing control of FHB to ensure high and stable wheat yields.