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Article

Preparation and Application of Multi-Walled Carbon Nanotube-Supported Metconazole Suspension Concentrate for Seed Coating to Control Wheat Sharp Eyespot

by
Xuexiang Ren
1,2,*,
Dongdong Qi
1,2,3,
Zhao Li
1,2,
Yu Chi
1,2,
Xianyan Su
1,2,
Kaixin Gu
1,2,
Zhenghe Ye
1,2,
Shun He
4 and
Li Chen
3
1
Institute of Plant Protection and Agro-Products Safety, Anhui Academy of Agricultural Sciences, Hefei 230001, China
2
Anhui Province Key Laboratory of Pesticide Resistance Management on Grain and Vegetable Pests, Hefei 230001, China
3
School of Plant Protection, Anhui Agricultural University, Hefei 230036, China
4
College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430074, China
*
Author to whom correspondence should be addressed.
Agronomy 2024, 14(9), 1985; https://doi.org/10.3390/agronomy14091985
Submission received: 4 July 2024 / Revised: 23 August 2024 / Accepted: 28 August 2024 / Published: 1 September 2024
(This article belongs to the Section Pest and Disease Management)
Browse Figures
Versions Notes

Abstract

:
Wheat sharp eyespot is a prevalent soil-borne disease that causes substantial economic losses in agriculture. Metconazole, a new triazole broad-spectrum fungicide, has demonstrated effective control of soil-borne diseases. Multi-walled carbon nanotubes (MWCNTs) are an innovative adsorbent material known for their large surface area and high absorptive capacity. This study identifies MWCNTs as the optimal adsorption material for metconazole, achieving an adsorption rate of 85.27% under optimal conditions (stirring time of 30 min and feeding ratio of 6:1). The optimized formula consists of 1.5% dispersant sodium wood, 1% emulsifier BY-112, 2% AEO-15, 3% glycol, 3% filmogen, and 4% red dyes. A 0.5% MWCNT–metconazole suspension concentrate for seed coating (FSC) significantly enhances the inhibitory effect of metconazole on wheat growth and promotes root development. At the tillering stage, a coating ratio of 1:100 shows a marked impact on wheat growth, and MWCNTs can improve the control effect of metconazole to Rhizoctonia cerealis. This work offers a novel approach for applying metconazole in a wheat suspension concentrate for seed coating.

1. Introduction

Wheat sharp eyespot (sheath blight) is a disease affecting the roots and stem bases of plants, caused by Rhizoctonia cerealis. This disease manifests as stem spotting, crown rot, seedling death, head blight, and other symptoms [1]. Wheat sharp eyespot has been reported in many areas of the world, including China, the United States, the United Kingdom, New Zealand, Egypt, South America, and Poland [2]. To date, no wheat germplasm has shown complete resistance to sharp eyespot, and only a few varieties have shown partial resistance [3]. Therefore, chemical fungicides remain a primary method for controlling wheat sharp eyespot.
Triazole fungicides were introduced in the 1970s and have seen a consistent increase in market share since then [4]. Metconazole, known chemically as 5-(4-chlorobenzyl)-2,2-dimethyl-1-(1H-1,2,4-triazol-1-ylmethyl) cyclopentanol, is a broad-spectrum triazole fungicide that inhibits ergosterol biosynthesis. It is widely used to control fungal disease such as wheat leaf rust, powdery mildew, and leaf blight [5]. However, there is no report on the application of metconazole as a seed coating agent to control wheat sharp eyespot because of the poor safety of metconazole to wheat seeds.
Seed coating agents are pesticide formulations made by processing active and inactive ingredients through specific processes. These agents can be applied directly or diluted and applied to the surface of seeds to form a pesticide coating. They are primarily used to prevent and control diseases and pests during the seeding stage, with smaller amounts applied in later stages of plant growth [6]. Additionally, seed coating agents can enhance seed germination, thereby improving the physiological and morphological properties of crops and increasing their yield [7].
Nanotechnology, as an interdisciplinary field, has engendered the formation of new disciplines such as nanophysics, nanobiology, nanochemistry, and nanoelectronics, all of which have been widely employed in research and industry [8]. The application of nanomaterials in the research and development of pesticide formulations is gaining popularity. Common nanomaterials include nano-silica, mesoporous carbon materials, and cyclodextrins. When diatomite is used to adsorb hymexazol, its slow release time can last for more than 25 days, with a maximum release rate above 70% [9]. Mesoporous silica nanoparticles loaded with pyrimethanil, pyraclostrobin, 2,4-dichlorophenoxy acetic acid, and azoxystrobin have demonstrated excellent slow-release properties and biological activity [10,11,12,13]. Multi-walled carbon nanotubes (MWCNTs) are a novel one-dimensional carbon-based nanomaterial known for their large specific surface area and strong adsorption capacity [14]. MWCNT-immobilized magnetic nanoparticles have demonstrated strong adsorption capacity for 2,4-D and atrazine [15]. Moreover, a previous study has found that MWCNTs reduce the phytotoxicity of quinclorac to tomatoes, significantly increasing the height and fresh weight of tomato plants and fruits [16].
Previous studies have found that metconazole-coated wheat seeds exhibit significant inhibitory effects on wheat sharp eyespot. In this study, metconazole, a triazole fungicide, was loaded onto MWCNTs. This study then compared two types of suspension concentrates for seed coating, one containing metconazole alone and the other containing metconazole adsorbed onto MWCNTs, both applied at the same concentration. This study will offer new strategies for preventing and controlling wheat sharp eyespot, provide a scientific basis for ensuring wheat security, and expand the application range of metconazole.

2. Materials and Methods

2.1. Plant Material, Fungal Pathogen, and Chemical Reagents

Wheat seeds (Yangmai 23, high sensitivity to R. cerealis) were provided by the Institute of Plant Protection and Agro-Product Safety at Anhui Academy of Agricultural Sciences. The R. cerealis strain was provided by the Laboratory of Plant Disease Prevalence and Comprehensive Treatment in the College of Plant Protection at Anhui Agricultural University. Naphthyl sulfonate formaldehyde condensation (NNO) was provided from Shandong Tongyi Chemical Co., Ltd. (Zibo, China). Lignin sulfonate was provided from Handan Cheng and Building Materials Co., Ltd. (Handan, China). Various emulsifiers, including polyethylene glycol 4000 (PEG4000), emulsifier TX-50, fatty alcohol ethoxylates (JFC-1), emulsifier HEL-40, BY-112 emulsifier, emulsifier EL-10, emulsifier O-10 and O-20, hard fatty acid polyether (SG-10 and SG-9), polyoxyethylene lauryl ether (MOA-7 and MOA-15), emulsifier S-20, polyethylene-polypropylene glycol (L-35 and L-65), polypropylene glycol 600 (PPG600), primary alcohol ethoxylate (E-1303, OS-15, and AEO-15), and polyether polyol HSH-206, were provided from Jiangsu Hai’an Petrochemical Factory (Nantong, China). Ethylene glycol was acquired from Shanghai Guangnuo Technology Co., Ltd. (Shanghai, China). Methyl alcohol was provided from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). Metconazole was provided from Anhui Jiuyi Agriculture Co., Ltd. (Hefei, China). MWCNTs were provided from Shenzhen Evolution Technology Co., Ltd. (Shenzhen, China).

2.2. Adsorption Rate and Loading Capacity of MWCNTs

To determine the maximum absorption peak of metconazole, a series of metconazole–methanol solutions of varying concentrations were prepared, using methanol as the reference solution. A UV–visible spectrophotometer was employed to scan the wavelength range of 200–400 nm to determine the location of the maximum absorption peak. For the construction of a metconazole standard curve, 0.1 g of metconazole was dissolved in methanol, and 990 μL of dimethyl sulfoxide (DMSO) was added to obtain a 1000 μg/mL dilution of the metconazole solution. Determined by a preliminary trial, the solution was used to prepare a concentration gradient of 20 μL, 40 μL, 60 μL, 80 μL, and 100 μL. The absorbance at 268 nm for each concentration was determined using a UV spectrophotometer, and the results were used to construct a standard curve for metconazole. For calculating the adsorption rate and loading capacity, 0.5 mL of the sample was added to a 10 mL centrifuge tube and diluted to 5 mL with a 30% methanol solution. The solution was centrifuged at 10,000 r/min for 5 min and allowed to stand at room temperature for 1 min. The absorbance of the solution was measured at 268 nm and compared with the methanol standard curve to determine the corresponding concentration from each absorbance value. The adsorption rate and loading capacity were calculated using the following formulas [17]:
Adsorption rate: R = (P0 − Pe)/P0
Loading capacity: L = [(P0 − Pe) × V]/M
where P0 is the initial mass concentration of the solution (mg/L); Pe is the mass concentration at solution equilibrium (mg/L); V is the solution volume (L); and M is the mass (g) of the metconazole-carrying preparation.
The main test steps for the preparation of MWCNT–metconazole were as follows [18]. Five feeding ratios (MWCNTs–metconazole) were set as 1:1, 2:1, 4:1, 6:1, and 8:1. Six time points were set as follows: 5 min, 10 min, 20 min, 30 min, 60 min, and 90 min. According to the dosage ratio, an appropriate amount of the metconazole was placed into a 100 mL conical bottle with 50 mL of a 40% methanol aqueous solution. After ultrasonication for 1 min to fully dissolve, 0.5 mL of the solution was transferred to a 1 mL centrifuge tube. The corresponding proportions of carbon tubes were weighed and added to the bottle to seal the adsorption system. The sealed conical bottle was placed on a constant temperature oscillator at 25 °C, 180 r/min. A 1 mL volume of the sample was taken at each specified time point and centrifuged for 10 min. A pipette was used to draw 0.5 mL of the supernatant, after which the supernatant was diluted 10 times and the absorbance was measured with a UV–visible spectrophotometer to obtain the adsorption rate and adsorption amount.

2.3. Selection of Different Adjuvant for the Suspension Concentrate for Seed Coating

The dispersant screening steps were as follows: four concentration gradients of sodium lignum and NNO were set at 1%, 1.5%, 2%, and 2.5%. The appropriate proportions of MWCNTs, metconazole, and pure water were added to a sand mill for grinding, along with a number of glass beads (at a ratio of approximately 1:3). During the grinding process, the dispersant corresponding to each concentration gradient was added. Samples were obtained using a glass rod every 30 min, diluted with water, and the particle size was determined using a laser particle size analyzer. The process continued until the particle size became balanced, at which point grinding was stopped and the range of particle sizes was recorded.
The steps for processing seed coating formulations were as described in a previous study [19]. The MWCNT–metconazole preparation was weighed, mixed with water, and homogenized. Each component (dispersant and emulsifier) was weighed according to the relevant ratio, added to a grinding and dispersing machine along with the grinding beads (approximately 150 g), and thoroughly mixed. The grinding machine was set to 3500 r/min. Glycol antifreeze was weighed and added to the grinder, and the formation of bubbles was observed. Every 30 min, samples were taken, and the particle size range was measured using a laser particle size analyzer until the particle size reached 5 μm or less. When the particle size met the requirements, grinding was stopped, and the grinding liquid was filtered for 30 min and poured out. The appropriate amounts of the film-forming agent and dye were added to the filtered sample, thoroughly mixed, and bottled for testing.

2.4. Development of the Suspension Concentrate for Seed Coating and Verification of Field Effect

Two different suspension concentrates for seed coating, 0.5% MWCNT–metconazole FSC and 0.5% metconazole FSC, were developed according to the screening formula by the wet sand grinding method.
The field experiment was carried out in the Hefei experimental base of Anhui Academy of Agricultural Sciences. The tested wheat variety was Yangmai 23, the coating ratio was set to 1:50 and 1:100, and the seeds were dried after uniform mixing. Each treatment was repeated 3 times with 15 plots, arranged randomly, with each plot covering an area of 25 m2, and 1 m protection rows left between each plot. Investigations were conducted at the seedling stage and tillering stage, respectively. A random fixed-point sampling method was adopted in each plot, and 30 wheat plants were sampled and measured at each point. Plant height (cm), root length (cm), fresh weight (g), dry weight (g), chlorophyll (SPAD), and nitrogen content (ng/g) were measured and recorded. Chlorophyll and nitrogen content were measured using a SPAD-502® Chlorophyll meter (Shuangxu Electronic Co., Ltd., Shanghai, China).

2.5. Effect of Metconazole Concentration on Wheat Sharp Eyespot under Controlled Conditions

The wheat sharp eyespot occurred very lightly under natural conditions for two years due to the weather. Therefore, a pot experiment was carried out by using the mixed method of fungal and soil inoculation.
The strain of R. cerealis was inoculated on a PDA medium for activation, and the medium was sealed and placed in a constant temperature incubator at 25 °C for 7 days. For the tests, 1 kg of sterilized soil was prepared in advance. Ten large dishes of R. cerealis were added to the sterilized soil, and mixed thoroughly. The coating ratio was set to 1:25, 1:50, 1:100, and 1:200. There were four replicates per treatment and 30 seeds per replicate. The seeds were evenly coated according to the relevant ratio. A total of 27 small plastic pots (diameter: 15 cm, height: 10 cm) containing 140 g of sterilized soil were prepared, and we added sterile water to saturate the soil, then sprinkled 20 g of mixed soil on the surface of the sterilized soil. The treated seeds were then evenly placed on the surface of the mixed soil and covered with 10 g of sterilized soil. The planted wheat was subsequently placed in an incubator (temperature: 25 °C, light/darkness = 12 h:12 h) for 25 days, and the incidence of wheat sharp eyespot was observed [20].

2.6. Statistical Analysis

The data are presented as the mean ± standard deviation. The statistical analysis of the data from each experiment was conducted using a one-way analysis of variance (ANOVA), followed by Tukey’s multiple-range test, as available on the SPSS 22.0® statistical package. The significance level for the data analysis was set at p < 0.05.

3. Results

3.1. Electron Microscope Pictures of MWCNTs

MWCNTs are a new type of nano-adsorption material with a large specific surface area and excellent adsorption capacity. Figure 1 shows electron microscope pictures of MWCNTs, where they appear as loosely entangled wire-like tubes with large specific surface area and good adsorption capacity.

3.2. Establishment of a Standard Curve for Metconazole

The ultraviolet (UV)–visible absorption spectrum of metconazole, measured using a UV-1900i spectrophotometer (Kojimazu Enterprise Management (China) Co., Ltd., Shanghai, China), revealed that the maximum absorption peak was at 202 nm. However, since methanol also absorbs at approximately 202 nm, this would interfere with the spectrophotometric measurements and affect the accuracy of the adsorption rate. Therefore, the second-largest absorption peak of metconazole, at 268 nm, was selected for accurate measurement. The UV absorption spectrum of metconazole is shown in Figure 2A. The standard curve for metconazole, established over a concentration range of 20–100 mg/L, exhibited a correlation coefficient of 0.99884, indicating a strong linear relationship and confirming the reliability of the standard curve for quantifying metconazole content in the solution (Figure 2B).

3.3. Optimum Preparation Conditions of MWCNTs–Metconazole

The adsorption rates at various feeding ratios increased during the first 30 min. At a feeding ratio (mass ratio) of 6:1, the rate of increase was relatively high. The growth rates at ratios of 4:1 and 8:1 were similar, while those at 1:1 and 2:1 were slower. After 30 min, the adsorption rates achieved equilibrium. The highest adsorption rate, 85.27%, was observed at a 6:1 ratio. In comparison, the rates were 63.15% at 4:1 and 82.29% at 8:1. The lowest rates occurred at 1:1 and 2:1, with values of 15.03% and 22.01%, respectively. As the feeding ratio increased from 1:1 to 6:1, there was a gradual increase in the adsorption rate of metconazole onto MWCNTs. However, at a feeding ratio of 8:1, the adsorption rate declined, possibly due to the excessive amount of MWCNTs resulting in a stirring adsorption process; i.e., a fraction of the metconazole molecules adsorbed on the surface of the MWCNTs returned to the solution. The optimal conditions for preparing MWCNT–metconazole involved a stirring time of 30 min and a feeding ratio of 6:1, which yielded the highest adsorption rate of 85.27% (Figure 3).

3.4. Determination of the Optimal Composition of the Suspension Concentrate for Seed Coating

3.4.1. Optimal Dispersant Selection

Different dispersants have variable effects on the system. In general, the volume mean diameter and area mean diameter are important indicators of the dispersion effect. The smaller the volume mean diameter and area mean diameter, the better the dispersion effect at a given concentration. When the concentration of sodium lignosulfonate was in the range of 1–2.5%, the volume and area mean diameters generally decreased initially and then increased, with the best dispersion effect observed at a concentration of 1.5%. This concentration resulted in a relatively narrow particle size range (Table 1). For NNO, within the same concentration range, the mean diameters also showed a trend of first decreasing and then increasing, with the best dispersion effect observed at a concentration of 2%. Based on these results, sodium lignosulfonate at a concentration of 1.5% was selected as the dispersant for the suspension concentrate used in seed coating.

3.4.2. Emulsifier and Antifreeze Selection

From the preliminary screening results for different emulsifiers, BY-112 and AEO-15 demonstrated good flow performance, with low delamination rates of 2.5% and 0, respectively, and no precipitation (Table 2). Other emulsifiers showed relatively poor flow performance, and high delamination rates or precipitation (Table 2). Therefore, BY-112 and AEO-15 were selected as emulsifiers for subsequent experiments, and orthogonal tests were performed to screen for suitable formulations.
According to the selection of the concentration range of ethanediol, the concentrations of glycol were determined to be 2%, 3%, and 4%. As shown in Table 3, when the concentrations of BY-112, AEO-15, and ethylene glycol were 1%, 2%, and 3%, respectively, the average area diameter and volume diameter of the system were the lowest at 16.16 μm and 30.27 μm, respectively. Finally, the optimal formula for the MWCNT–metconazole wheat seed coat emulsifier was determined to be 1% BY-112, 2% AEO-15, and 3% ethanediol, with the latter also serving as an antifreeze.

3.5. The Field Effect of Different Suspension Concentrates for Seed Coating

The 0.5% MWCNT–metconazole FSC could significantly improve the inhibitory effect of metconazole on wheat growth, and significantly promote the growth of wheat roots. At the tillering stage, the 1:100 coating ratio showed a marked effect on wheat growth (Figure 4).

3.5.1. The Field Effect of Different Suspension Concentrates for Seed Coating at the Seedling Stage

Under the same coating ratio, plants treated with FSC (DM) showed significantly greater height than those treated with FSC (M), indicating that MWCNTs facilitated a slow-release effect for metconazole, reducing its inhibitory impact on wheat growth (Figure 5A). The root length of plants treated with FSC (DM) at a 1:100 ratio was significantly greater than other treatments (Figure 5B). Additionally, the fresh weight and dry weight of plants treated with FSC (DM) were higher than other treatments (Figure 5C,D), demonstrating that MWCNTs effectively promoted dry matter accumulation in wheat seedlings. There were no significant differences in SPAD and nitrogen content among the different treatments (Figure 5E,F).

3.5.2. The Field Effect of Different Suspension Concentrates for Seed Coating at the Tillering Stage

The plant height and number of tillers in plants treated with FSC (M) were significantly lower than those in other treatments. In contrast, plants treated with FSC (DM) at a 1:100 ratio exhibited significantly greater plant height compared to the other treatments (Figure 6A,B). Both the fresh weight and dry weight were significantly lower than CK, except in plants treated with FSC (DM) at a 1:100 ratio (Figure 6C,D). There were no significant differences in SPAD and nitrogen content among the different treatments (Figure 6E,F).

3.6. FSC (DM) Treatment Significantly Improves the Effectiveness of Wheat Sharp Eyespot

The coating ratios ranged from 1:25 to 1:200. After treatment with the 0.5% MWCNT–metconazole seed coating agent, the control effects at coating ratios of 1:25, 1:50, 1:100, and 1:200 were 86.14%, 82.25%, 75.86%, and 67.42%, respectively. The control effect of FSC (DM) was significantly higher than that of FSC (M) (Table 4).

4. Discussion

Wheat is one of the world’s three major food crops, and wheat farmers suffer hundreds of millions of dollars of losses each year due to soil-borne fungal diseases [21,22,23]. Triazole fungicides are effective against soil-borne diseases of wheat and are widely used as wheat seed coating agents [24]. Metconazole, a triazole fungicide, has a significant control effect on wheat sharp eyespot. As a pesticide formulation, the suspension concentrate for seed coating has excellent effects in soil-borne disease control. In this study, the carrier material and the adsorption conditions were carefully screened and optimized, and various auxiliary additives were examined. Finally, a 0.5% MWCNT–metconazole suspension concentrate for seed coating was developed. The quality and control efficacy of this formulation were thoroughly compared to a 0.5% metconazole suspension concentrate for seed coating.
Carbon nanotubes (CNTs), also known as buckytubes, are a new type of carbon nanomaterial first synthesized by Japanese scientists in 1991 [25]. MWCNTs are coaxial circular tubes composed of several or dozens of layers of graphene sheets stabilized by van der Waals forces between the layers. The layer spacing is generally approximately 0.34 nm, the tube diameter is 2–30 nm, and the tube’s length is 0.1–50 μm [26]. MWCNTs have been shown to improve the repair efficiency of the hyperaccumulator Solanum nigrum L. under cadmium and arsenic stress [27]. Five-walled CNTs could efficiently absorb diazinon [28]. Additionally, increasing the content of MWCNTs in soil to 0.5% and 1% significantly reduced the phytotoxicity of quinclorac to tomato plants, promoting their growth [16]. In this study, a constant temperature oscillation method was used to prepare the pesticide-carrying preparation. Due to the high viscosity of MWCNTs in water, the adsorption was weakened at high ratios, determining the optimal ratio of metconazole in the seed coating agent to be 0.5%.
Traditional pesticide-type seed coating agents benefit the germination and growth of crop seeds [29,30]. For example, a seed coating agent increased the growth factors of plant height, root length, fresh weight, and dry weight of cotton seedlings, which increased by 52.70%, 25.13%, 46.47%, and 33.21%, respectively [31]. Furthermore, two Streptomyces strains (S. roche D74 and S. pactum Act12) significantly affected the biological characteristics, photosynthesis, and biochemical metabolism of maize seedlings, promoting root development, plant growth, and yield [32]. Although metconazole has good activity against wheat sharp eyespot, it being used as a seed coating ingredient has not been explored due to its poor safety for wheat seeds. Considering the controlled-release properties of MWCNTs, this study utilized MWCNTs to adsorb metconazole, thereby reducing potential pesticide damage.
The results of this study showed that a 0.5% MWCNT–metconazole seed coating had greater safety than a 0.5% metconazole seed coating with a sustained release effect on metconazole. In field experiments, wheat growth treated with the 0.5% MWCNT–metconazole seed coating was lower than that of the blank control at pesticide-to-seed ratios of 1:50 and 1:100. MWCNTs significantly alleviated the pesticide damage of metconazole to wheat seeds, making it possible to apply metconazole to the seed coating. Furthermore, there was a small inhibitory effect on the growth of wheat seedlings at 1:50 due to the partial release of the original pesticide from the pores and walls of the carrier material during processing. Regarding the tillering stage, wheat treated with 0.5% MWCNT–metconazole FSC showed significantly better growth compared to those treated with 0.5% metconazole FSC alone, with no signs of growth inhibition. This suggests that MWCNTs had a significant controlled-release effect on metconazole.
In addition to promoting plant growth, seed coating agents can effectively reduce the damage caused by diseases and pests [33,34]. For example, wheat seeds coated with Streptomyces sp. strain DEF39 spores had a reduced risk of Fusarium head blight [35]. In addition, using imidacloprid as a seed coating agent on oilseed rape effectively reduced aphid damage [36]. Here, the efficacy of 0.5% MWCNT–metconazole and 0.5% metconazole seed coatings in controlling wheat sharp eyespot was evaluated through field experiments. The results showed that the incidence of wheat sharp eyespot was significantly lower in plants treated with the 0.5% MWCNT–metconazole seed coating compared to those treated with the 0.5% metconazole seed coating, likely due to the slow release of metconazole from the MWCNTs. However, this experiment only assessed the treatments’ effectiveness during the early stages of wheat growth, limiting the ability to fully examine the slow-release performance of the pesticide-loaded seed coating. Future studies will investigate the pharmacodynamics of wheat across multiple growth stages to gather more comprehensive data. Research will also explore the mechanism of promoting growth, soil microbial changes, and metconazole residues, focusing on the sustained release after MWCNTs adsorb metconazole.

5. Conclusions

The application of seed coating agents has benefited agricultural production. In this study, the proportion of metconazole as an active ingredient in seed coating agents was 0.5%. The formulation of MWCNTs–metconazole for wheat seed coatings was determined to be 0.5% MWCNTs–metconazole, 1.5% dispersant sodium lignum, 1% emulsifier BY-112, 3% AEPO-15, 3% glycol as an antifreeze, 3% film-forming agent, and 4% dye. Laboratory safety tests showed that the 0.5% MWCNT–metconazole seed coating agent was highly safe. Furthermore, the 0.5% MWCNT–metconazole seed coating had a better control effect on wheat sharp eyespot than a 0.5% metconazole seed coating, with a control effect reaching 86.14% at a metconazole-to-seed ratio of 1:25. This research provides data supporting the use of metconazole as a seed coating agent to control wheat sharp eyespot.

Author Contributions

X.R.: Conceptualization; Formal analysis; Methodology; Visualization; and Writing—original draft and review and editing. D.Q.: Investigation; Data curation; Writing—original draft; and Methodology. Z.L.: Project administration; Data curation; and Funding acquisition. Y.C.: Investigation; Formal analysis; and Validation. X.S.: Investigation; Formal analysis; and Validation. K.G.: Formal analysis; and Supervision of resource allocation. Z.Y. and S.H.: Investigation; and Formal analysis. L.C.: Supervision of resource allocation; Validation; and Writing—review and editing. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by the Youth Talents Project of Anhui Academy of Agricultural Sciences (QNYC-202213).

Data Availability Statement

The data are contained within the article.

Conflicts of Interest

The authors declare no conflicts of interest.

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Agronomy 14 01985 g001
Figure 1. Electron microscope pictures of MWCNTs.
Figure 1. Electron microscope pictures of MWCNTs.
Agronomy 14 01985 g001
Agronomy 14 01985 g002aAgronomy 14 01985 g002b
Figure 2. Establishment of standard curve for metconazole. (A) Ultraviolet absorption spectrum of metconazole; (B) standard curve for metconazole.
Figure 2. Establishment of standard curve for metconazole. (A) Ultraviolet absorption spectrum of metconazole; (B) standard curve for metconazole.
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Figure 3. Adsorption curves for different MWCNT inputs over time. The abscissa reflects time, and the ordinate indicates the adsorption rate. The gray, red, blue, green, and purple lines represent ratios of 1:1, 2:1, 4:1, 6:1, and 8:1, respectively.
Figure 3. Adsorption curves for different MWCNT inputs over time. The abscissa reflects time, and the ordinate indicates the adsorption rate. The gray, red, blue, green, and purple lines represent ratios of 1:1, 2:1, 4:1, 6:1, and 8:1, respectively.
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Figure 4. The field effect of 0.5% MWCNT–metconazole FSC (DM) and 0.5% metconazole FSC (M) at the seedling stage (top) and tillering stage (bottom). CK: the blank control.
Figure 4. The field effect of 0.5% MWCNT–metconazole FSC (DM) and 0.5% metconazole FSC (M) at the seedling stage (top) and tillering stage (bottom). CK: the blank control.
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Figure 5. Plant height (A), root length (B), fresh weight (C), dry weight (D), SPAD (E), and nitrogen content (F) of 0.5% MWCNT–metconazole FSC (DM) and 0.5% metconazole FSC (M) at seedling stage. Significant differences are marked by letters (Student’s t-test, p < 0.05).
Figure 5. Plant height (A), root length (B), fresh weight (C), dry weight (D), SPAD (E), and nitrogen content (F) of 0.5% MWCNT–metconazole FSC (DM) and 0.5% metconazole FSC (M) at seedling stage. Significant differences are marked by letters (Student’s t-test, p < 0.05).
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Figure 6. Plant height (A), number of tillers (B), fresh weight (C), dry weight (D), SPAD (E), and nitrogen content (F) of 0.5% MWCNT–metconazole FSC (DM) and 0.5% metconazole FSC (M) at tillering stage. Significant differences are marked by letters (Student’s t-test, p < 0.05).
Figure 6. Plant height (A), number of tillers (B), fresh weight (C), dry weight (D), SPAD (E), and nitrogen content (F) of 0.5% MWCNT–metconazole FSC (DM) and 0.5% metconazole FSC (M) at tillering stage. Significant differences are marked by letters (Student’s t-test, p < 0.05).
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Table 1. Selection testing for the dispersant concentration.
Table 1. Selection testing for the dispersant concentration.
Dispersant and Concentration (%)Volume Mean Diameter (μm)Area Mean Diameter (μm)
Sodium
lignosulfonate		132.91 ± 0.47 d21.86 ± 0.67 d
1.524.72 ± 1.88 g14.81 ± 1.14 g
228.11 ± 4.13 f16.15 ± 3.02 e
2.530.63 ± 0.43 e15.46 ± 1.33 f
NNO137.76 ± 1.04 b25.35 ± 1.16 b
1.533.80 ± 1.90 c23.51 ± 1.75 c
234.86 ± 1.31 c20.82 ± 2.59 d
2.545.13 ± 1.21 a30.35 ± 2.03 a
Note: Data are shown as the mean ± SE; significant differences are marked by letters (Student’s t-test, p < 0.05).
Table 2. Preliminary selection experiment for emulsifier.
Table 2. Preliminary selection experiment for emulsifier.
NumberLayering Rate (%)
PEG40007.5 ± 0.26 k
TX-5010.0 ± 0.77 j
JFC-165.0 ± 3.21 a
HEL-405.0 ± 0.14 l
BY-1122.5 ± 0.10 m
EL-1017.5 ± 1.10 h
O-1020.0 ± 1.71 g
SG-1067.5 ± 3.20 a
SG-965.0 ± 3.31 a
MOA-730.0 ± 2.10 c
MOA-1530.0 ± 1.55 c
S-2027.5 ± 1.77 d
L-6525.0 ± 1.35 e
PPG60045.0 ± 2.10 b
L-3522.5 ± 1.66 f
O-2012.5 ± 0.71 i
E-130310.0 ± 0.52 j
OS-1517.5 ± 1.21 h
AEO-150 ± 0.00 n
HSH-2065.0 ± 0.41 l
Note: Data are shown as the mean ± SE; significant differences are marked by letters (Student’s t-test, p < 0.05).
Table 3. Orthogonal experiment results for the emulsifier and antifreeze.
Table 3. Orthogonal experiment results for the emulsifier and antifreeze.
NumberBY-112 (%)AEO-15 (%)Ethynediol (%)Area Mean Diameter (μm)Volume Mean Diameter (μm)
111220.58 ± 0.29 e31.57 ± 0.51 g
212316.16 ± 1.22 f30.27 ± 2.91 g
313415.51 ± 1.60 f40.48 ± 2.11 f
421321.36 ± 0.6 e38.71 ± 2.19 f
522442.63 ± 2.36 c81.78 ± 2.68 d
623229.09 ± 0.78 d88.43 ± 4.68 c
731465.99 ± 7.99 a136.46 ± 4.69 a
832257.12 ± 7.26 b125.82 ± 7.15 b
933320.35 ± 0.75 e47.85 ± 2.01 e
Note: Data are shown as the mean ± SE; significant differences are marked by letters (Student’s t-test, p < 0.05).
Table 4. Control effect of FSC (DM) and FSC (M) on wheat sharp eyespot.
Table 4. Control effect of FSC (DM) and FSC (M) on wheat sharp eyespot.
TreatmentCoating Ratio (g/g)Disease IndexControl Efficiency (%)
0.5% MWCNT–metconazole FSC (DM)1:253.17 ± 0.55 e86.14 ± 0.37 a
1:504.13 ± 1.45 de82.25 ± 0.91 ab
1:1005.40 ± 1.09 de75.86 ± 1.09 ab
1:2007.30 ± 0.54 cde67.42 ± 0.56 abc
0.5% metconazole FSC (M)1:256.98 ± 3.06 cde68.61 ± 1.13 abc
1:508.57 ± 4.95 bcd61.04 ± 0.47 bcd
1:10010.48 ± 3.43 bc52.60 ± 0.87 cd
1:20012.38 ± 1.90 b45.12 ± 0.66 d
CK—22.86 ± 3.30 a—
Note: Data are shown as the mean ± SE; significant differences are marked by letters (Student’s t-test, p < 0.05). CK means control treated with noting.
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Ren, X.; Qi, D.; Li, Z.; Chi, Y.; Su, X.; Gu, K.; Ye, Z.; He, S.; Chen, L. Preparation and Application of Multi-Walled Carbon Nanotube-Supported Metconazole Suspension Concentrate for Seed Coating to Control Wheat Sharp Eyespot. Agronomy 2024, 14, 1985. https://doi.org/10.3390/agronomy14091985

AMA Style

Ren X, Qi D, Li Z, Chi Y, Su X, Gu K, Ye Z, He S, Chen L. Preparation and Application of Multi-Walled Carbon Nanotube-Supported Metconazole Suspension Concentrate for Seed Coating to Control Wheat Sharp Eyespot. Agronomy. 2024; 14(9):1985. https://doi.org/10.3390/agronomy14091985

Chicago/Turabian Style

Ren, Xuexiang, Dongdong Qi, Zhao Li, Yu Chi, Xianyan Su, Kaixin Gu, Zhenghe Ye, Shun He, and Li Chen. 2024. "Preparation and Application of Multi-Walled Carbon Nanotube-Supported Metconazole Suspension Concentrate for Seed Coating to Control Wheat Sharp Eyespot" Agronomy 14, no. 9: 1985. https://doi.org/10.3390/agronomy14091985

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