Fungicides from rice cultivation (tebuconazole and azoxystrobin) alters biochemical and histological markers of hammertoad tadpoles (Boanafaber).

Tebuconazole (TBZ) and azoxystrobin (AZX) are fungicides frequently used in rice cultivation. Despite protecting crops against fungal diseases, these compounds can contaminate the natural environments close to the crops, exerting negative effects on non-target organisms, the present study aimed to characterize the contamination by fungicides of a river that flows in an area dominated by rice cultivation in the north of the state of Santa Catarina, SC, Brazil. Concentrations of TBZ and AZX found in the field were used to evaluate their negative effects on development, biochemical biomarkers and histopatology of the liver of a native tadpole species, the hammerfrog (Boana faber). Tadpoles were exposed for 16 days to the lowest (1.20 µg/L) and highest (2.60 µg/L) concentration of TBZ, lowest (0.70 µg/L) and highest (1.60 µg/L) concentration of AZX, and the mix of both fungicides at lowest and highest concentration of each found in field analyses. Exposure to the lower TBZ concentration and both concentrations of the Mix accelerated the development of tadpoles. AZX caused an increase in the activities of glutathione S-transferase (GST), carboxylesterase (CbE) and glucose-6-phosphate dehydrogenase (G6PDH) in the liver, an increase in the levels of protein carbonyls (PC) in the liver and an increase in the activity of acetylcholinesterase (AChE) in muscle of tadpoles. TBZ, on the other hand, generated an increase in GST, G6PDH, PC and histopathological severity scores in liver and in muscle AChE activity. The effects were more intense in the groups exposed to the Mix of contaminants. No treatment altered brain AChE. The data showed that the fungicides from in rice cultivation found in natural aquatic environments around the crops pose risks to the health of the animals, compromising their metabolism and development.

Higher fitness and competitive advantage of Pyricularia oryzae Triticum lineage resistant to QoI fungicides.

BACKGROUND: Quinone outside inhibitor (QoI) fungicides have not been effective in controlling the wheat blast disease [Pyricularia oryzae Triticum lineage (PoTl)] in Brazil. The first report of resistance of PoTl to QoIs in this country occurred in 2015. This study aimed to test hypotheses about the changes in fitness parameters and competitive advantage of the QoI-resistant (R) PoTl isolate group compared to the sensitive (S) isolate group. Mycelial growth on PDA medium and in vivo conidial production, incubation period and disease severity were analyzed as fitness parameters. The competitive ability was measured on wheat leaves and heads inoculated with mixtures of R:S isolates at the following proportions: 0S:100R, 20S:80R, 50S:50R, 80S:20R, 100S:0R, and 0S:0R. RESULTS: The QoI-R isolate group had significantly higher fitness than the sensitive isolate group, considering both in vitro and in vivo parameters. The highest in vivo conidial production on wheat leaves and the highest leaf and head disease severity were detected when resistant strains were predominant in the isolate's mixtures (20S:80R or 0S:100R proportions), in the absence of fungicide pressure. Conidia harvested from wheat blast lesions on leaves inoculated with 20S:80R and 0S:100R mixtures were resistant to QoIs in vitro assays based on discriminatory doses of the fungicide. CONCLUSION: Therefore, QoI resistance facilitated a higher fitness and a competitive advantage in PoTl, which contrasts with the evolutionary theory that associates a fitness cost to fungicide resistance. We discuss the evolutionary and ecological implications of the higher fitness as found in the fungicide-resistant adapted populations of the wheat blast pathogen. © 2022 Society of Chemical Industry.

Virulence of native isolates of entomopathogenic fungi (Hypocreales) against the "sweetpotato whitefly" Bemisia tabaci (Hemiptera: Aleyrodidae), including the effects of temperature and fungicides.

Hypocrella, Moelleriella and related species in the Hypocreales (Ascomycota, Sordariomycetes) cause epizootics of whiteflies and scale insects in nature. However, studies on their host specificity, virulence, infection cycles, optimal development under laboratory conditions, and compatibility with other control methods, are unexplored for most species. Under laboratory conditions, the virulence of several isolates of field-collected hypocrealean fungi (Hypocrella, Moelleriella, Regiocrella, and Verticillium) was determined on Bemisia tabaci eggs and 4th instar nymphs. In addition to virulence, the effect of temperature and two commercial fungicides on growth rates and germination of the isolates was evaluated. None of the isolates infected the eggs, while M. libera, M. ochracea, and M. turbinata caused high nymphal mortality. Moelleriella libera was the most virulent isolate. At all temperatures, M. libera, Regiocrella sp. (P17H20), and Verticillium cf. pseudohemipterigenum had the highest germination and growth rates. The optimal growth temperature depended on the isolate, but at 23 °C and 25 °C, the probability of spore germination was higher for most isolates. Finally, the fungicides azoxystrobin and chlorothalonil inhibited growth rates and conidial germination at 24 and 48 h of exposure. This research produces vital knowledge on the virulence and infection cycles of poorly studied native species of entomopathogenic fungi. In addition, the results provide information on the optimal temperature for development in laboratory conditions and susceptibility to fungicides, which could contribute to future biological control strategies.

Degradation of pesticides present in tomato rinse water by direct photolysis and UVC/H2O2: optimization of process conditions through sequential Doehlert design.

The degradation of three pesticides, azoxystrobin (AZO), difenoconazole (DFZ), and imidacloprid (IMD), commonly found in the tomato rinse water, was studied through UVC (251-257 nm) and UVC/H2O2 photolysis. The results showed that direct photolysis follows pseudo-first-order kinetics, with total AZO and IMD removals within 15 min, using 21.8 and 28.6 W m-2, respectively, while the highest percentage of DFZ degradation was 51.7% at 28.6 W m-2 UVC. The estimated quantum yields were 0.572, 0.028, and 0.061 mol Einstein-1 for AZO, DFZ, and IMD, respectively. With regard to UVC/H2O2, total pesticide removal was achieved after 10 min, while optimal treatment conditions in relation to the pesticide removal rates, estimated through the sequential Doehlert design, were about [H2O2]0 = 130 mg L-1 and 26 W m-2. Cytotoxicity and genotoxicity assays carried out with Allium cepa, for real industrial tomato rinse water sampled from washing belts did not show abnormalities during cell division, with total pesticides degradation after 15 min, demonstrating the potential application of the UVC/H2O2 process as a viable localized treatment with a focus on the possible reuse of treated water.

Environmentally relevant pesticides induce biochemical changes in Nile tilapia (Oreochromis niloticus).

The high demand for food consequently increases the entry of agricultural residues into water resources, and this phenomenon can affect non-target organisms in different ways. Environmentally relevant pesticide effects (per se or in combinations) are scarce in the scientific literature. Therefore, the aim of this study was to investigate: (1) the presence of pesticide residues in an important Brazilian source of water supply and power generation (Jacuí river), during 1 year of monitoring. (2) in a laboratory study verify the effects of the most frequently, herbicide, fungicide, and insecticide found in Jacuí river (individualized or in a mixture) on biochemical parameters in different tissues of Oreochromis niloticus. Twenty pesticide residues were detected in superficial water samples, and two of them are banned in Brazilian territory. Atrazine (0.56 µg L-1), azoxystrobin (0.024 µg L-1), and imidacloprid (0.11 µg L-1) were the most frequently herbicide, fungicide, and insecticide, respectively, found in the river and were used in the laboratory assay. O. niloticus exposed to the pesticide mixture exhibited more biochemical effects than individualized exposure groups. This response can be a result of the combined pesticide effects, culminating in an additive or synergistic effect, depending on the biomarker. In individual exposure groups, atrazine presented the most pronounced alterations, followed by azoxystrobin and imidacloprid. Overall, pesticide exposure increased levels of oxidative stress parameters, reduced antioxidant enzyme activities, and induced acetylcholinesterase activity. These findings highlight the threat to aquatic organisms which may be exposed to a miscellaneous of toxic compounds in the environment.

Effect of household rice cooking on pesticide residues.

This investigation shows the pesticide distribution and reduction using three common household cooking methods. Extraction was performed using QuEChERS and solid phase microextraction methodologies for rice and water, respectively. Gas chromatography-mass spectrometry was used. Both methods showed good linearity (r2 > 0.9996 and 0.9945), adequate recoveries (between 98.9 and 107.8% and 90.5-104.2%) and relative standard deviations lower than 4.5% and 7.0%, for rice and water, respectively. The initial concentration of deltamethrin, penconazole, kresoxim-methyl, cyproconazole, epoxiconazole and azoxystrobin, were 84.9, 242.2, 298.5, 230.7, 253.4 and 293.5 µg/kg, respectively. Washing and soaking water reduce pesticides only 0.40 to 4.28%. The pesticide reduction during cooking were 20.73 to 57.72%, 32.74 to 70.39%, and 68.87 to 87.50% for traditional, excess water, and pre-soaking rice methods, respectively. Pre-soaking rice with extra water before cooking proved to be the method that generates the greatest reduction.

Use of ozone and detergent for removal of pesticides and improving storage quality of tomato.

The efficiencies of two conventional domestic procedures (immersion in pure water and detergent solution at 0.25 and 1%) and two treatments using ozone (immersion in water with bubbling O3 and immersion in ozonated water, both at 1 and 3 mg L-1) were evaluated for the removal of residues of the fungicides azoxystrobin, chlorothalonil and difenoconazole in tomatoes. The fungicides were sprayed on the fruits at the recommended concentration for the crop. The residues in the tomatoes and in the washing solutions were determined by extraction with low-temperature partition techniques and analysis by gas chromatography. More concentrated solutions were more effective in removing pesticide residues. The water bubbled with ozone at 3 mg L-1 was the most efficient treatment for the removal of fungicides, reaching a reduction of 70-90% of the residues. However, the treatments with the lowest concentration of ozone had lower loss of fruit mass during storage.

Physiological, biochemical, and nutritional parameters of wheat treated with a fungicide and foliar fertilizer / Parâmetros fisiológicos, bioquímicos e nutricionais em trigo tratado com fungicida e fertilizante foliar

Agronomic improvements in grain yield and quality of wheat crops could be obtained through the application of strategies, such as using foliar fungicides with fertilizers, to protect the leaves against pathogens and delay senescence during grain filling. However, few studies have reported the effect of these practices on wheat, although these treatments could represent a new method of increasing wheat production and profits. The objective of this study was to evaluate the effects of foliar fertilizer, applied alone or in combination with a fungicide, on the photochemical, biochemical, and nutritional parameters of wheat plants. The experiment was conducted under greenhouse conditions in a 2 × 3 factorial design (fungicide × foliar fertilizer) with four replications. The fungicide treatment used was azoxystrobin + cyproconazole + mineral oil; the control was left untreated. The foliar fertilizer was used at two different rates, and the control was not treated. Plants were sprayed at the GS29/GS30, GS45, and GS60 growth stages, and the plants were assessed ten days after the last spray. Chlorophyll a fluorescence, the photochemical efficiency of photosystem II (Fv/Fm), and electron transport rate were positively influenced by fertilizer. Fertilizer spraying significantly increased the leaf pigment content (chlorophylls a and b and carotenoids) and the nitrogen, phosphorus, and...

Melhorias no rendimento e qualidade de grãos na cultura do trigo poderiam ser obtidas através da implementação de estratégias, como a utilização de fungicidas com fertilizantes foliares, para proteção das folhas contra patógenos e retardo da senescência durante o enchimento de grãos. Entretanto, poucos estudos têm reportado o efeito destas práticas em trigo, embora estes tratamentos possam representar incrementos na produção de trigo e maiores lucros. O objetivo deste trabalho foi avaliar o efeito do fertilizante foliar aplicado isolado ou em associação com fungicida, em parâmetros fotoquímicos, bioquímicos e nutricionais em plantas de trigo. O ensaio foi conduzido em condições de casa de vegetação em esquema fatorial 2 × 3 (fungicida x fertilizante) com quatro repetições. O fungicida utilizado foi azoxistrobina + ciproconazol + óleo mineral; o controle foi deixado sem tratamento. O fertilizante foliar foi utilizado em duas doses, e o controle não foi tratado. As plantas foram pulverizadas nos estágios GS29/GS30, GS45 e GS60, e as plantas foram avaliadas dez dias após a última aplicação. Os parâmetros da fluorescência da clorofila a, eficiência fotoquímica máxima do fotossistema II (Fv/ Fm) e taxa de transporte de elétrons foram positivamente influenciados pelo fertilizante. A aplicação do fertilizante significativamente incrementou o conteúdo de pigmentos foliares...

Physiological, biochemical, and nutritional parameters of wheat treated with a fungicide and foliar fertilizer / Parâmetros fisiológicos, bioquímicos e nutricionais em trigo tratado com fungicida e fertilizante foliar

Agronomic improvements in grain yield and quality of wheat crops could be obtained through the application of strategies, such as using foliar fungicides with fertilizers, to protect the leaves against pathogens and delay senescence during grain filling. However, few studies have reported the effect of these practices on wheat, although these treatments could represent a new method of increasing wheat production and profits. The objective of this study was to evaluate the effects of foliar fertilizer, applied alone or in combination with a fungicide, on the photochemical, biochemical, and nutritional parameters of wheat plants. The experiment was conducted under greenhouse conditions in a 2 × 3 factorial design (fungicide × foliar fertilizer) with four replications. The fungicide treatment used was azoxystrobin + cyproconazole + mineral oil; the control was left untreated. The foliar fertilizer was used at two different rates, and the control was not treated. Plants were sprayed at the GS29/GS30, GS45, and GS60 growth stages, and the plants were assessed ten days after the last spray. Chlorophyll a fluorescence, the photochemical efficiency of photosystem II (Fv/Fm), and electron transport rate were positively influenced by fertilizer. Fertilizer spraying significantly increased the leaf pigment content (chlorophylls a and b and carotenoids) and the nitrogen, phosphorus, and...(AU)

Melhorias no rendimento e qualidade de grãos na cultura do trigo poderiam ser obtidas através da implementação de estratégias, como a utilização de fungicidas com fertilizantes foliares, para proteção das folhas contra patógenos e retardo da senescência durante o enchimento de grãos. Entretanto, poucos estudos têm reportado o efeito destas práticas em trigo, embora estes tratamentos possam representar incrementos na produção de trigo e maiores lucros. O objetivo deste trabalho foi avaliar o efeito do fertilizante foliar aplicado isolado ou em associação com fungicida, em parâmetros fotoquímicos, bioquímicos e nutricionais em plantas de trigo. O ensaio foi conduzido em condições de casa de vegetação em esquema fatorial 2 × 3 (fungicida x fertilizante) com quatro repetições. O fungicida utilizado foi azoxistrobina + ciproconazol + óleo mineral; o controle foi deixado sem tratamento. O fertilizante foliar foi utilizado em duas doses, e o controle não foi tratado. As plantas foram pulverizadas nos estágios GS29/GS30, GS45 e GS60, e as plantas foram avaliadas dez dias após a última aplicação. Os parâmetros da fluorescência da clorofila a, eficiência fotoquímica máxima do fotossistema II (Fv/ Fm) e taxa de transporte de elétrons foram positivamente influenciados pelo fertilizante. A aplicação do fertilizante significativamente incrementou o conteúdo de pigmentos foliares...(AU)

Physiological changes promoted by a strobilurin fungicide in the rice-Bipolaris oryzae interaction.

Strobilurins are among the most important fungicides that are used for plant disease control worldwide. In addition to their fungicide effect, strobilurins can also improve crop physiology. Nonetheless, the impact of azoxystrobin (Az), the main marketed strobilurin, on rice physiology is still unknown. Detailed gas exchange measurements and chlorophyll a fluorescence analysis were used to examine the Az effects on the photosynthetic performance of rice plants (cultivar Metica-1) either challenged or not with Bipolaris oryzae, the causal agent of brown spot. Az impaired carbon (C) fixation in the non-inoculated plants in a manner that was not related to photochemical or biochemical limitations, but rather to decreased stomatal conductance that limited the CO2 influx into the mesophyll cells. The photosynthesis of rice plants that were not sprayed with Az dramatically decreased upon B. oryzae infection, which was chiefly governed by photochemical and biochemical limitations. The energy surplus that was caused by limited C fixation in the rice plants that were treated with Az and inoculated with B. oryzae was thermally and effectively dissipated until 72h after inoculation. In Az absence, however, this mechanism was not sufficient to prevent chronic photoinhibition to photosynthesis. The inoculated plants were not able to fully capture and exploit the collected light energy, but these constraints were greatly limited in the presence of Az. In conclusion, Az impaired the photosynthetic performance of non-infected plants by diffusive constraints, but prevented, to a greater extent, the damage to the photosynthetic apparatus during the infection process of B. oryzae.

Physiological responses in the banana plantlets treateds with strobilurins / Respostas fisiológicas em mudas de banananeira tratadas com estrobilurinas

There are reports that strobilurin besides having a fungicide effect can promote physiologic benefits to the plants. However, this effect on banana plants was not studied yet. The objective of the present study was to evaluate the effect of strobirulins on the physiology of banana plantlets. For this purpose, cultivar Grand Naine banana plantlets were transferred to pots containing substrate and kept in a nursery with 50% shading. The experimental design was a completely randomized design with three treatments (water, azoxystrobin and pyraclostrobin) and five replications. The treatments were applied at 15, 30, 45, 60 and 75 days after transplanting at a dose 100 g a. i. ha-1 with manual spray. Plant height, pseudostem diameter, shoot dry matter in strobilurin treated plants were higher than the untreated plants, however, the effect of fungicide treatment was different, being the most pronounced effect of pyraclostrobin compared to azoxystrobin. Plants treated with pyraclostrobin had higher leaf area, nitrate reductase activity and chlorophyll content of leaf total nitrogen than the plants treated with azoxystrobin and water, which did not differ. Strobilurins affect the physiology of the banana plantlets differently, the effect being more pronounced by pyraclostrobin.

Há relatos de que estrobilurinas, além de atuarem como fungicida, promovem benefícios fisiológicos às plantas. Assim sendo, o presente trabalho teve como objetivo avaliar o efeito de estrobirulinas na fisiologia de mudas de bananeira. Para tal, mudas micropropagadas da cultivar Grand Naine foram repicadas para vasos contendo substrato e mantidas em viveiro a 50% de sombreamento. O delineamento experimental foi inteiramente casualizado, com três tratamentos (água, azoxistrobina e piraclostrobina) e cinco repetições. As estrobirulinas foram aplicadas com pulverizador manual aos 15, 30, 45, 60 e 75 dias após a repicagem, na dose de 100 g i. a. ha-1. A altura da planta, diâmetro do pseudocaule e a massa da matéria seca da parte aérea de plantas tratadas com estrobilurinas foram superiores às de plantas não tratadas. O efeito do tratamento com fungicidas foi diferenciado, sendo mais pronunciado nas plantas tratadas com piraclostrobina do que nas plantas tratadas com azoxistrobina. Plantas tratadas com piraclostrobina apresentaram área foliar, atividade da redutase do nitrato e teor de clorofila a e de nitrogênio total foliar superiores às plantas tratadas com azoxistrobina e água, que não diferiram entre si. As estrobilurinas afetaram a fisiologia das mudas de bananeira, com destaque para a piraclostrobina.

Physiological responses in the banana plantlets treateds with strobilurins / Respostas fisiológicas em mudas de banananeira tratadas com estrobilurinas

There are reports that strobilurin besides having a fungicide effect can promote physiologic benefits to the plants. However, this effect on banana plants was not studied yet. The objective of the present study was to evaluate the effect of strobirulins on the physiology of banana plantlets. For this purpose, cultivar Grand Naine banana plantlets were transferred to pots containing substrate and kept in a nursery with 50% shading. The experimental design was a completely randomized design with three treatments (water, azoxystrobin and pyraclostrobin) and five replications. The treatments were applied at 15, 30, 45, 60 and 75 days after transplanting at a dose 100 g a. i. ha-1 with manual spray. Plant height, pseudostem diameter, shoot dry matter in strobilurin treated plants were higher than the untreated plants, however, the effect of fungicide treatment was different, being the most pronounced effect of pyraclostrobin compared to azoxystrobin. Plants treated with pyraclostrobin had higher leaf area, nitrate reductase activity and chlorophyll content of leaf total nitrogen than the plants treated with azoxystrobin and water, which did not differ. Strobilurins affect the physiology of the banana plantlets differently, the effect being more pronounced by pyraclostrobin.

Há relatos de que estrobilurinas, além de atuarem como fungicida, promovem benefícios fisiológicos às plantas. Assim sendo, o presente trabalho teve como objetivo avaliar o efeito de estrobirulinas na fisiologia de mudas de bananeira. Para tal, mudas micropropagadas da cultivar Grand Naine foram repicadas para vasos contendo substrato e mantidas em viveiro a 50% de sombreamento. O delineamento experimental foi inteiramente casualizado, com três tratamentos (água, azoxistrobina e piraclostrobina) e cinco repetições. As estrobirulinas foram aplicadas com pulverizador manual aos 15, 30, 45, 60 e 75 dias após a repicagem, na dose de 100 g i. a. ha-1. A altura da planta, diâmetro do pseudocaule e a massa da matéria seca da parte aérea de plantas tratadas com estrobilurinas foram superiores às de plantas não tratadas. O efeito do tratamento com fungicidas foi diferenciado, sendo mais pronunciado nas plantas tratadas com piraclostrobina do que nas plantas tratadas com azoxistrobina. Plantas tratadas com piraclostrobina apresentaram área foliar, atividade da redutase do nitrato e teor de clorofila a e de nitrogênio total foliar superiores às plantas tratadas com azoxistrobina e água, que não diferiram entre si. As estrobilurinas afetaram a fisiologia das mudas de bananeira, com destaque para a piraclostrobina.

Fungicide resistance and genetic variability in plant pathogenic strains of Guignardia citricarpa / Resistência a fungicidas e variabilidade genética em linhagens patogênicas de plantas Guignardiacitricarpa

Citrus black spot (CBS) is a plant disease of worldwide occurrence, affecting crops in Africa, Oceania, and South America. In Brazil, climate provides favorable conditions and CBS has spread to the Southeast and South regions. CBS is caused by the fungus Guignardia citricarpa (anamorph: Phyllosticta citricarpa) and its control is based on the use of fungicides, such as benzimidazoles. In South Africa, the disease was kept under control for 10 years with benomyl, until cases of resistance to high concentrations of this fungicide were reported from all citrus-producing areas. Azoxystrobin (a strobilurin) has been found effective in controlling phytopathogens, including CBS, in a wide range of economically important crops. The present study investigated in vitro the effects of the fungicides benomyl and azoxystrobin on 10 strains of G. citricarpa isolated from lesions in citrus plants from Brazil and South Africa. Benomyl at 0.5 µg/mL inhibited mycelial growth in all strains except PC3C, of African origin, which exhibited resistance to concentrations of up to 100.0 µg/mL. The spontaneous mutation frequency for resistance to benomyl was 1.25 ï 10-7. Azoxystrobin, even at high concentrations, did not inhibit mycelial growth in any of the strains, but significantly reduced sporulation rates, by as much as 100%, at a concentration of 5.0 µg/mL. Variations in sensitivity across strains, particularly to the strobilurin azoxystrobin, are possibly related to genetic variability in G. citricarpa isolates.

A Mancha Preta dos Citros (MPC) tem ocorrência mundial afetando a produção de citros na África, Oceania e América do Sul. No Brasil, onde o clima é favorável ao seu desenvolvimento, a doença está espalhada nas regiões Sul e Sudeste. O controle da MPC, causada pelo fungo Guignardia citricarpa (anamorfo: Phyllosticta citricarpa) é baseado na aplicação de fungicidas, como os benzimidazóis. Na África do Sul, após 10 anos de controle da doença com o fungicida benomil, os casos de resistência a altas concentrações deste fungicida atingiram todas as áreas produtoras. O fungicida estrolilurina chamado azoxistrobina tem se mostrado eficiente no controle dos fitopatógenos de uma grande variedade de culturas economicamente importantes, incluindo a MPC. Neste trabalho foram investigados os efeitos in vitro dos fungicidas benomil e azoxistrobina em 10 linhagens de G. citricarpa isoladas de lesões em plantas cítricas no Brasil e na África do Sul. Houve inibição do crescimento micelial a 0,5 µg/mL do fungicida benomil entre as linhagens testadas, com exceção de PC3C de origem sul-africana, que apresentou resistência até a concentração de 100,0 µg/mL de benomil. A freqüência de mutação espontânea para resistência ao benomil foi de 1,25 ï 10-7. A estrobilurina azoxistrobina, mesmo em altas concentrações, não inibiu o crescimento micelial dos isolados, entretanto reduziu significativamente a produção de esporos, chegando a 100% de inibição em concentrações de 5,0 µg/mL de azoxistrobina. A variação na sensibilidade das linhagens, principalmente com a estrobilurina azoxistrobina, possivelmente está relacionada com a variabilidade genética dos isolados de G. citricarpa.

Fungicide resistance and genetic variability in plant pathogenic strains of Guignardia citricarpa.

Citrus black spot (CBS) is a plant disease of worldwide occurrence, affecting crops in Africa, Oceania, and South America. In Brazil, climate provides favorable conditions and CBS has spread to the Southeast and South regions. CBS is caused by the fungus Guignardia citricarpa (anamorph: Phyllosticta citricarpa) and its control is based on the use of fungicides, such as benzimidazoles. In South Africa, the disease was kept under control for 10 years with benomyl, until cases of resistance to high concentrations of this fungicide were reported from all citrus-producing areas. Azoxystrobin (a strobilurin) has been found effective in controlling phytopathogens, including CBS, in a wide range of economically important crops. The present study investigated in vitro the effects of the fungicides benomyl and azoxystrobin on 10 strains of G. citricarpa isolated from lesions in citrus plants from Brazil and South Africa. Benomyl at 0.5 µg/mL inhibited mycelial growth in all strains except PC3C, of African origin, which exhibited resistance to concentrations of up to 100.0 µg/mL. The spontaneous mutation frequency for resistance to benomyl was 1.25 × 10(-7). Azoxystrobin, even at high concentrations, did not inhibit mycelial growth in any of the strains, but significantly reduced sporulation rates, by as much as 100%, at a concentration of 5.0 µg/mL. Variations in sensitivity across strains, particularly to the strobilurin azoxystrobin, are possibly related to genetic variability in G. citricarpa isolates.

Fungicide resistance and genetic variability in plant pathogenic strains of Guignardia citricarpa

Citrus black spot (CBS) is a plant disease of worldwide occurrence, affecting crops in Africa, Oceania, and South America. In Brazil, climate provides favorable conditions and CBS has spread to the Southeast and South regions. CBS is caused by the fungus Guignardia citricarpa (anamorph: Phyllosticta citricarpa) and its control is based on the use of fungicides, such as benzimidazoles. In South Africa, the disease was kept under control for 10 years with benomyl, until cases of resistance to high concentrations of this fungicide were reported from all citrus-producing areas. Azoxystrobin (a strobilurin) has been found effective in controlling phytopathogens, including CBS, in a wide range of economically important crops. The present study investigated in vitro the effects of the fungicides benomyl and azoxystrobin on 10 strains of G. citricarpa isolated from lesions in citrus plants from Brazil and South Africa. Benomyl at 0.5 µg/mL inhibited mycelial growth in all strains except PC3C, of African origin, which exhibited resistance to concentrations of up to 100.0 µg/mL. The spontaneous mutation frequency for resistance to benomyl was 1.25 ´ 10-7. Azoxystrobin, even at high concentrations, did not inhibit mycelial growth in any of the strains, but significantly reduced sporulation rates, by as much as 100%, at a concentration of 5.0 µg/mL. Variations in sensitivity across strains, particularly to the strobilurin azoxystrobin, are possibly related to genetic variability in G. citricarpa isolates.

A Mancha Preta dos Citros (MPC) tem ocorrência mundial afetando a produção de citros na África, Oceania e América do Sul. No Brasil, onde o clima é favorável ao seu desenvolvimento, a doença está espalhada nas regiões Sul e Sudeste. O controle da MPC, causada pelo fungo Guignardia citricarpa (anamorfo: Phyllosticta citricarpa) é baseado na aplicação de fungicidas, como os benzimidazóis. Na África do Sul, após 10 anos de controle da doença com o fungicida benomil, os casos de resistência a altas concentrações deste fungicida atingiram todas as áreas produtoras. O fungicida estrolilurina chamado azoxistrobina tem se mostrado eficiente no controle dos fitopatógenos de uma grande variedade de culturas economicamente importantes, incluindo a MPC. Neste trabalho foram investigados os efeitos in vitro dos fungicidas benomil e azoxistrobina em 10 linhagens de G. citricarpa isoladas de lesões em plantas cítricas no Brasil e na África do Sul. Houve inibição do crescimento micelial a 0,5 µg/mL do fungicida benomil entre as linhagens testadas, com exceção de PC3C de origem sul-africana, que apresentou resistência até a concentração de 100,0 µg/mL de benomil. A freqüência de mutação espontânea para resistência ao benomil foi de 1,25 FONT FACE=Symbol>´ /font> 10-7. A estrobilurina azoxistrobina, mesmo em altas concentrações, não inibiu o crescimento micelial dos isolados, entretanto reduziu significativamente a produção de esporos, chegando a 100% de inibição em concentrações de 5,0 µg/mL de azoxistrobina. A variação na sensibilidade das linhagens, principalmente com a estrobilurina azoxistrobina, possivelmente está relacionada com a variabilidade genética dos isolados de G. citricarpa.

Efeito de fungicidas no controle da ferrugem do feijoeiro causada por uromyces appendiculatus em condições de campo / Fungicides effects on the control of leaf bean rust caused by uromyces appendiculatus under field conditions

RESUMO Avaliou-se a eficácia de fungicidas no controle da ferrugem do feijoeiro, em condições de campo. O experimento foi conduzido em Marília, SP, com plantas de feijão do grupo Carioca. Foram realizadas 3 pulverizações a cada 14 dias, utilizando-se 300 L de calda/ha, com os ingredientes ativos: trifloxystrobin + propiconazole (75 mL/ha), prothioconazole (100 mL ha-1); azoxystrobin (50 g ha-1) + nimbus 0,25% v/v e trifloxystrobin + tebuconazole (50 + 100, 60 + 120 e 75 + 150 mL ha-1). O controle proporcionado pelos ingredientes ativos foi avaliado nas folhas, sendo o índice de infecção calculado através de escala de notas dividida em nove níveis. Constatou-se q ue todos os fungicidas e doses utilizados foram eficientes no controle da ferrugem (Uromyces appendiculatus), proporcionando mais de 90% de eficiência. Na testemunha o índice de infecção chegou a 52% na terceira avaliação.

ABSTRACT The efficacy of fungicides for the controlof bean rust was evaluated, under field conditions. The experiment was conducted in Marília, SP (Brasil), using bean plants of the 'Carioca' group. Three sprayings were applied, each 14 days, with spray volume of 300 liters ha-1, with the following active ingredients: trifloxystrobin + propiconazole (75 mL ha-1), prothioconazole (100 mL ha-1), azoxystrobin (50 g ha-1) + nimbus 0,25% v/v and trifloxystrobin + tebuconazole (50 + 100, 60 + 120 and 75 + 150 mL ha-1). The disease control provided by active ingredients was evaluated on leaves, with its infection index calculated from a 9-degree disease index. All the fungicides and their doses used were efficient in controlling leaf bean rust (Uromyces appendiculatus), reaching more than 90% efficiency. In the control treatment the leaf infection index reached 52% at the third evaluation.