Chemical seed treatment and mycorrhizal inoculation provide better development and nutrition of common bean plants.

BACKGROUND: Chemical seed treatment is an established practice in agriculture to protect crops from soil-borne pathogens and pests. Arbuscular mycorrhizal fungi (AMF) benefit plants by extending soil exploration as well as water and nutrient uptake. The objective of this work was to analyze the effects of combinations of seed treatments with doses of inoculant containing Rhizoglomus intraradices on vegetative development, root colonization and nutrition of Phaseolus vulgaris plants and soil microbiota. RESULTS: Seed treatment benefited the vegetative development and nutrition of beans, with the treatments metalaxyl + fludioxonil + tiabendazole and pyraclostrobin + thiophanate methyl + fipronil standing out regarding the contents of nitrogen (N), phosphorus (P), iron (Fe) and zinc (Zn) of the aerial parts. Mycorrhizal inoculation linearly increased dehydrogenase activity, root biomass and total plant biomass, with increments reaching 27%. There was an interaction between seed treatment and inoculation dose for aboveground biomass and the contents of potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), manganese (Mn) and root colonization, with expressive results for the combination of the two highest doses of inoculant with metalaxyl + fludioxonil + tiabendazole or pyraclostrobin + methylthiophanate + fipronil in the seeds. CONCLUSION: Chemical seed treatment and mycorrhizal inoculation benefited bean plants and their nutritional status. The best combinations for the bean crop were metalaxyl + fludioxonil + tiabendazole with 41.4 mg of the inoculant per 100 seeds and pyraclostrobin + thiophanate methyl + fipronil with 62.1 mg of the inoculant per 100 seeds. © 2022 Society of Chemical Industry.

Maternal and developmental toxicity after exposure to formulation of chlorothalonil and thiophanate-methyl during organogenesis in rats.

Chlorothalonil and thiophanate-methyl are fungicides widely used in agriculture. The aim of this study was to assess maternal toxicity and embryotoxic potential of exposure to chlorothalonil and thiophanate-methyl during organogenesis period in rats. Pregnant rats were divided into four groups: control and exposed to 400 (CT400), 800 (CT800) and 1200 mg-1kg bw-1 day (CT1200) of commercial formulation constituted of 200 g of thiophanate-methyl kg-1 and 500 g of chlorothalonil kg-1 by gavage, from 6th to 15th gestational day. Maternal toxicity, liver, kidney and placenta histology, reproductive performance, and external, skeletal and visceral malformations of fetuses were evaluated. Maternal liver weight was decreased in CT1200 group and focal necrosis and microvesicular steatosis, inflammatory infiltrate and hepatocytes with pyknotic nucleus were observed in CT800 and CT1200 groups. Reproductive performance was similar among groups. The percentage of fetuses small for pregnancy age was increase in CT400 and CT800 groups. Moreover, incidence of skeletal anomalies was increased in the three groups exposed to fungicides. Chlorothalonil and thiophanate-methyl exposure showed affect the prenatal development and induce maternal toxicity.

Reduced sensitivity of azoxystrobin and thiophanate-methyl resistance in Lasiodiplodia theobromae from papaya.

Stem-end rot caused by Lasiodiplodia theobromae is one of the most devastating diseases of papaya in northeastern Brazil. It is most effectively controlled by applications of fungicides, including site-specific fungicides at risk for resistance development. This study investigated the molecular mechanisms of reduced sensitivity to the QoI fungicide azoxystrobin and resistance to the MBC fungicide thiophanate-methyl in L. theobromae from Brazilian orchards. The EC50 values for azoxystrobin in sixty-four isolates ranged from 0.36 µg/ml to 364.24 µg/ml and the frequency distribution of EC50 values formed a multimodal curve, indicating reduced sensitivity to azoxystrobin. In detached fruit assays reduced sensitive isolates were not controlled as effectively as sensitive isolates at lowest label rate. Partial fragments were obtained from target genes ß-tubulin (751 bp) and Cytb (687 bp) of isolates resistant to thiophanate-methyl and reduced sensitivity to azoxystrobin. Sequence analysis of the ß-tubulin fragment revealed a mutation corresponding to E198K in all thiophanate-methyl-resistant isolates, while reduced sensitivity to axoxystrobin was not attributable to Cytb gene alterations. The target gene-based mechanism conferring resistance to thiophanate-methyl will likely be stable even if selection pressure subsides. However, the mechanism conferring reduced sensitivity to azoxystrobin is not based on target gene modifications and thus may not be as stable as other genotypes with mutations in Cytb gene.

Sensitivity of Botrytis cinerea Isolates from Conventional and Organic Strawberry Fields in Brazil to Azoxystrobin, Iprodione, Pyrimethanil, and Thiophanate-Methyl.

Botrytis fruit rot, caused by Botrytis cinerea, is one of the most important strawberry diseases worldwide, and fungicide applications are often used to manage the disease in commercial production. Isolates of B. cinerea were collected from conventional and organic strawberry fields in four Brazilian States from 2013 to 2015 and their sensitivity to the main single-site mode-of action fungicides used in Brazil was tested. Resistance to azoxystrobin, iprodione, pyrimethanil, and thiophanate-methyl was found and values for effective concentration that inhibited mycelial growth by 50% were higher than 71.9, 1.2, 5.0, and 688 µg/ml, respectively, regardless the production system. Resistance to these fungicides was observed in 87.5, 76.6, 23.4, and 92.2% of isolates from conventional fields and 31.4, 22.9, 14.3, and 51.4% of isolates from organic fields, respectively. Moreover, frequencies of isolates with multiple fungicide resistance to the four active ingredients were 20.6 and 2.8% whereas 6.3 and 27.8% were sensitive to the four fungicides for conventional and organic areas, respectively. Molecular analyses of the cytochrome b, ß-tubulin, and bos1 genes revealed the presence of G143A; E198A; and I365 N/S, Q369P, or N373S mutations, respectively, in resistant isolates of B. cinerea. Field rates of fungicides sprayed preventively to inoculated strawberry fruit failed to control disease caused by the respective resistant isolates.

Thiophanate-Methyl Resistance and Fitness Components of Colletotrichum musae Isolates from Banana in Brazil.

Anthracnose, caused by Colletotrichum musae, is the most important postharvest disease of banana and is widely distributed among the banana production regions in Brazil. Although thiophanate-methyl is a fungicide frequently used in Brazilian banana orchards to control Sigatoka leaf spot, Collettotrichum populations are also exposed, resulting in the evolution of fungicide resistance and the inability to manage banana anthracnose. We investigated 139 Brazilian isolates of C. musae for thiophanate-methyl sensitivity in vitro. The 50% mycelial growth inhibition (EC50) values varied between 0.003 and 48.73 µg/ml. One-hundred and thirty isolates were classified as sensitive, with EC50 values ranging from 0.003 to 4.84 µg/ml, while the remaining nine isolates were considered moderately resistant, with EC50 values ranging between 10.43 and 48.73 µg/ml. Resistant or highly resistant isolates (EC50 > 100 µg/ml) were not found. A substitution of TAC for TTC at codon 200 in a coding region of the ß-tubulin gene was associated with the moderately resistant phenotype. Applications of thiophanate-methyl formulation to detached banana fruit at the label rate (500 µg/ml) showed low efficacy in controlling the moderately resistant isolates on banana fruits. However, there is no indication of a reduction in fitness associated with fungicide resistance as sensitive and moderately resistant isolates do not differ with respect to mycelial growth rate (P = 0.098), spore production (P = 0.066), spore germination (P = 0.366), osmotic sensitivity (P = 0.051), and virulence (P = 0.057). Our results revealed absence of adaptability cost for the moderately resistant isolates, suggesting that they can be dominant in population if the fungicide continue to be applied.

MSPD sample preparation approach for reversed-phase liquid chromatographic analysis of pesticide residues in stem of coconut palm.

A method was developed using matrix solid-phase dispersion, together with liquid chromatography with ultraviolet diode array detector for determination of carbofuran, difenoconazole, ß-cyfluthrin, spirodiclofen and thiophanate-methyl in stem of coconut palm. The best results were obtained using 2.0 g of stem, 1.6 g of Florisil as sorbent and cyclohexane:acetone mixture (4:1). The method was validated using stem samples spiked with pesticides at four concentration levels (0.05-2.0 µg/g). Average recoveries ranged from 70 % to 114.3 %, with relative standard deviations between 1.2 % and 19.2 %. Detection and quantification limits were in the ranges 0.02-0.03 and 0.05-0.1 µg/g, respectively.

Investigating phenotypic variability in Colletotrichum lindemuthianum populations.

Colletotrichum lindemuthianum, causal agent of anthracnose in the common bean, has wide genetic variability. Differential bean cultivars and morphological and physiological characteristics were used to analyze 74 isolates of C. lindemuthianum collected in two counties in the state of Minas Gerais, Brazil. Six different races were found, with a predominance of race 65 at both locations. Isolates were classified according to their sensitivities to the fungicide thiophanate-methyl, normally used in the control of common bean anthracnose. In all, ≈10% of isolates were resistant to the fungicide in vitro. Characteristics such as indexes of mycelia growth rate, colony diameter, sporulation capacity, and percentage of germination demonstrated the high genetic variability of C. lindemuthianum. We also observed variation in conidial cytology. The conidia of most isolates showed septa formation after germination, in contrast to septa absence, previously reported in the literature. Sexual and asexual reproduction were evaluated for mechanisms that may contribute in the generation of variability in C. lindemuthianum. Conidial anastomosis tubes were commonly found, indicating that asexual reproduction can help increase variability in this species. Information from this study confirmed high variability in C. lindemuthianum and will guide future studies in basic knowledge and applied technologies.

Determinaçäo do fungicida tiofanato metílico por espectrofotometria infravermelha / Determination of the methyl thiophanate fungicide by infrared spectrophotometry

A presente pesquisa descreve método por espectrofotometria infravermelha desenvolvido para analisar tiofanato metílico técnico e suas formulaçöes. Foi utilizada absorçäo em 9,43 mum/1.060 cm(-1), valor correspondente à ligaçäo C-O-, característica da molécula de tiofanato metílico. Concluiu-se que o método estabelecido é adequado para análise de tiofanato metílico, demonstrando exatidäo e precisäo.

A new primary screening test for anthelmintics utilizing the parasitic stages of Nippostrongylus brasiliensis, in vitro.

A new in vitro test suitable for the large scale screening of chemical compounds for anthelmintic activity is described. The test which utilizes the fourth larval and adult stages of Nippostrongylus brasiliensis in a medium capable of supporting the growth and development of the parasite, detects selectively those compounds which possess either broad spectrum anthelmintic or specific anti-trichostrongyle activity. The screen is easy to operate requiring only minute quantities of experimental compound. It renders fully reproducible results which furthermore can be interpreted objectively. This is the first reported in vitro test directed against the parasitic stages of a nematode that is capable of detecting reliably the activity of a wide range of anthelmintics including thiophanate and all the benzimidazoles.