Absence Of Fungicide Research Articles

Host Genetic Resistance in Brassica napus: A Valuable Tool for the Integrated Management of the Fungal Pathogen Leptosphaeria maculans.

Management of plant disease in agro-ecosystems ideally relies on a combination of host genetic resistance, chemical control, and cultural practices. Growers increasingly rely on chemical and genetic options, but their relative benefits in disease control, yield, and economic outcomes are rarely quantified. We explore this relationship for blackleg crown canker disease (caused by Leptosphaeria maculans), a major biotic constraint limiting canola production globally. Data from 20 field trials conducted from 2013 to 2015 in canola-growing regions of Australia were used to assess the effects of host resistance and fungicide treatment on blackleg severity, grain yield, and gross margin. In the absence of fungicide, blackleg disease was 88% lower in the most resistant compared with the most susceptible blackleg resistance category. In the most susceptible resistance category, the most effective fungicide treatment significantly reduced blackleg severity (from 50 to 6%) and increased grain yield (478 kg/ha, 41%) and gross margin (AU$120/ha, 17%). However, the mean benefits of fungicide tended to decrease with increasing levels of genetic resistance, to the point that yield, disease, and gross margin benefits were close to zero in the most resistant cultivars. Overall, these findings suggest that fungicides can reduce blackleg severity, but the benefits of application strongly depend on associated levels of genetic resistance. Canola cultivars with higher genetic resistance reliably reduced blackleg disease and maintained grain yield without the associated cost of fungicide application. The intensification of canola production to meet increasing global demand will require strategies to sustainably manage and protect finite genetic resistance resources to control blackleg disease.

Leaf Species-Dependent Fungicide Effects on the Function and Abundance of Associated Microbial Communities

Microbially-mediated leaf litter decomposition is a critical ecosystem function in running waters within forested areas, which can be affected by fungicides. However, fungicide effects on leaf litter decomposition have been investigated almost exclusively with black alder leaves, a leaf species with traits favourable to consumers (i.e., low recalcitrance and high nutrient content). At the same time, little is known about fungicide effects on microbial colonisation and decomposition of other leaf species with less favourable traits. In this 21 day lasting study, we explore the effects of increasing fungicide sum concentrations (0–3000 µg/L) on microbial colonisation and decomposition of three leaf species (black alder, Norway maple and European beech) differing in terms of recalcitrance and nutrient content. Leaf litter decomposition rate, leaf-associated fungal biomass and bacterial density were quantified to observe potential effects at the functional level. Beech, as the species with the least favourable leaf traits, showed a substantially lower decomposition rate (50%) in absence of fungicides than alder and maple. In the presence of high fungicide concentrations (300–3000 µg/L), beech showed a concentration-related decrease not only in microbial leaf litter decomposition but also fungal biomass. This suggests that favourable traits of leaf litter (as for alder and maple) enable leaf-associated microorganisms to acquire leaf-bound energy more easily to withstand potential effects induced by fungicide exposure. Our results indicate the need to deepen our understanding on how leaf species’ traits interact with the impact of chemical stressors on the leaf decomposition activity of microbial communities.

SdhC-I86F Mutation in Phakopsora pachyrhizi Is Stable and Can Be Related to Fitness Penalties.

Succinate dehydrogenase inhibitors (SDHIs) fungicides are used to control Asian soybean rust (Phakopsora pachyrhizi), and the SdhC-I86F mutation is related to pathogen resistance. The objective of this study was to determine whether fitness penalties are associated with SDHI resistance (SdhC-I86F mutation) in P. pachyrhizi populations. Moreover, the study investigated whether the SdhC-I86F mutation remained stable after the fungus propagation both in the absence and presence of fungicide. The populations used in this study presented mutations for all genes analyzed (Cyp51, Cytb, and SdhC), except for a wild-type population (WTSdhC) found with no SdhC-I86F mutation. The frequencies of the SdhC-I86F mutant populations were stable after 36 generations in the absence of fungicide. However, in the case of the WTSdhC population, the SdhC-I86F mutation was further detected after one generation of the fungus in the presence of the SDHI fungicide, according to the results of a detached leaf assay. Three tests were performed to evaluate fitness components and sensitivity to fungicides (half maximal effective concentration). SdhC-I86F mutant populations were more sensitive to osmotic and oxidative stress than the WTSdhC population; however, the sensitivity to ultraviolet radiation was similar for both populations. All mutated populations were less sensitive than the WTSdhC when using SDHI (azoxystrobin + benzovindiflupyr), but more sensitive to mancozeb. The presence of fitness penalties, the mutation stability, and the sensitivity to mancozeb presented by the SdhC-I86F mutant populations can be relevant to the management of the disease in the field.

Wheat Yield Response to Nitrogen Rate Depends on Foliar Fungicide Application

Nitrogen (N) and fungicide are among the most important factors impacting wheat yields in Kansas. However, there is limited information on whether foliar fungicides interact with N rates in wheat yield determination. Thus, our objectives were to evaluate wheat yield as impacted by different N rates with or without the use of foliar fungicide. One field experiment was established using a factorial structure of five N rates (0, 30, 60, 90, and 120 pounds of N per acre) by two fungicide management practices (either absent or 13 fluid ounces per acre of Nexicor) in a split-plot design near Hutchinson, KS, during the 2020–2021 wheat growing season. The variety Larry was planted at 90 pounds of seed per acre, N was the whole plot and fungicide was the subplot. There was a significant interaction between N and fungicide on winter wheat grain yield, where the benefit of fungicide was greater with higher N rates. In the absence of fungicide, wheat yields ranged from 51.1 bushels per acre in the zero N rate, to 68.5 bu/a in the highest N rate. Meanwhile, grain yield ranged from 57.3 bu/a when no N was applied, to 83.8 bu/a in the highest N rate. Despite higher yields when fungicides were applied, grain yield within fungicide treatment plateaued at the 90 pounds of N per acre rate. This experiment provided initial empirical evidence for the interaction between N management and fungicide. More field experiments are expected to validate this in future years.

As above, so below? Effects of fungicides on microbial organic matter decomposition are stronger in the hyporheic than in the benthic zone

AbstractMicrobial organic matter decomposition is a critical ecosystem function, which can be negatively affected by chemicals. Although the majority of organic matter is stored in sediments, the impact of chemicals has exclusively been studied in benthic systems. To address this knowledge gap, we assessed the impact of a fungicide mixture at three concentrations on the decomposition of black alder leaves in the benthic and hyporheic zone. We targeted two sediment treatments characterized by fine and coarse grain sizes (1–2 vs. 2–4 mm). Besides microbial communities' functioning (i.e., decomposition), we determined their structure through microbial biomass estimates and community composition. In absence of fungicides, leaf decomposition, microbial biomass estimates and fungal sporulation were lower in the hyporheic zone, while the importance of bacteria was elevated. Leaf decomposition was reduced (40%) under fungicide exposure in fine sediment with an effect size more than twice as high as in the benthic zone (15%). These differences are likely triggered by the lower hydraulic conductivity in the hyporheic zone influencing microbial dispersal as well as oxygen and nutrient fluxes. Since insights from the benthic zone are not easily transferable, these results indicate that the hyporheic zone requires a higher recognition with regard to ecotoxicological effects on organic matter decomposition.

Plant diversity ameliorates the evolutionary development of fungicide resistance in an agricultural ecosystem

Abstract The evolution of fungicide resistance in agricultural and natural ecosystems is associated with the biology of pathogens, the chemical property and application strategies of the fungicides. The influence of ecological factors such as host diversity on the evolution of fungicide resistance has been largely overlooked but is highly relevant to social and natural sustainability. In this study, we used an experimental evolution approach to understand how host population heterogeneity may affect the evolution of fungicide resistance in the associated pathogens. Potato populations with six levels of genetic heterogeneity were grown in the same field and naturally infected by Phytophthora infestans. Pathogen isolates (~1,200) recovered from the field experiment were molecularly genotyped. Genetically distinct isolates were selected from each population and 142 isolates were assayed for their tolerance to two fungicides differing in the mode of action. Tolerance was determined by calculating the relative growth rate of the isolates in the presence and absence of fungicides and the effective concentration for 50% inhibition. The evolution of fungicide resistance in P. infestans was affected by the genetic variation of host populations. Higher potato diversification increased the sensitivity of P. infestans to both fungicides and reduced genetic variation of the pathogen available for the development of fungicide resistance. These mitigating effects are independent of biochemical properties of fungicides and are likely caused by host selection for pathogen strains differing in the ability of fungicide influxes, effluxes or detoxification rather than mutations in fungicide target genes. Synthesis and applications. The development of fungicide resistance greatly threatens food security and ecological sustainability, and it is urgent need to develop agricultural practices which can ameliorate this problem. Our results show that potato crop with a higher genetic diversity is associated with a late blight pathogen of higher fungicide sensitivity and lower potential of developing fungicide resistance, indicating that agricultural diversification such as through cultivar mixture can reduce the application dose and frequency of fungicides needed to achieve the same level of disease control, which, in turn, further reduce the selection pressure acting on the pathogen populations and the evolutionary risk of developing fungicide resistance in pathogens. Together with benefits documented in other studies, our results indicate that crop diversification is an eco‐friendly approach that not only ameliorate fungicide resistance but also help achieve social and ecological sustainability by balancing the interaction among food security, socio‐economic development and ecological resilience and should be promoted.

Bottom-up effects of fungicides on tadpoles of the European common frog (Rana temporaria).

Biodiversity is under pressure worldwide, with amphibians being particularly threatened. Stressors related to human activity, such as chemicals, are contributing to this decline. It remains, however, unclear whether chemicals exhibiting a fungicidal activity could indirectly affect tadpoles that depend on microbially conditioned leaf litter as food source. The indirect effect of fungicides (sum concentration of a fungicide mixture composed of azoxystrobin, carbendazim, cyprodinil, quinoxyfen, and tebuconazole: 100 µg/L) on tadpoles was assessed relative to leaf litter colonized by microbes in absence of fungicides (control) and a worst‐case scenario, that is leached leaf litter without microbial colonization. The quality of leaf litter as food for tadpoles of the European common frog (Rana temporaria) was characterized through neutral lipid fatty acid profiles and microbial sum parameters and verified by sublethal responses in tadpoles (i.e., feeding rate, feces production, growth, and fatty acid composition). Fungicides changed the nutritious quality of leaf litter likely through alterations in leaves’ neutral lipid fatty acid profiles (i.e., changes in some physiologically important highly unsaturated fatty acids reached more than 200%) in combination with a potential adsorption onto leaves during conditioning. These changes were reflected by differences in the development of tadpoles ultimately resulting in an earlier start of metamorphosis. Our data provide a first indication that fungicides potentially affect tadpole development indirectly through bottom‐up effects. This pathway is so far not addressed in fungicide environmental risk assessment and merits further attention.

Effects of foliar fungicide on yield, micronutrients, and cadmium in grains from historical and modern hard winter wheat genotypes.

Plant breeding and disease management practices have increased the grain yield of hard winter wheat (Triticum aestivum L.) adapted to the Great Plains of the United States during the last century. However, the effect of genetic gains for seed yield and the application of fungicide on the micronutrient and cadmium (Cd) concentration in wheat grains is still unclear. The objectives of this study were to evaluate the effects of fungicide application on the productivity and nutritional quality of wheat cultivars representing 80 years of plant breeding efforts. Field experiments were conducted over two crop years (2017 and 2018) with eighteen hard winter wheat genotypes released between 1933 and 2013 in the presence or absence of fungicide application. For each growing season, the treatments were arranged in a split-plot design with the fungicide levels (treated and untreated) as the whole plot treatments and the genotypes as split-plot treatments in triplicate. The effects on seed yield, grain protein concentration (GPC), micronutrients, phytic acid, and Cd in grains were measured. While the yield of wheat was found to increase at annualized rates of 26.5 and 13.0 kg ha-1 yr-1 in the presence and absence of fungicide (P < 0.001), respectively, GPC (-190 and -180 mg kg-1 yr-1, P < 0.001), Fe (-35.0 and -44.0 μg kg-1 yr-1, P < 0.05), and Zn (-68.0 and -57.0 μg kg-1 yr-1, P < 0.01) significantly decreased during the period studied. In contrast to the other mineral elements, grain Cd significantly increased over time (0.4 μg kg-1 yr-1, P < 0.01) in the absence of fungicide. The results from this study are of great concern, as many mineral elements essential for human nutrition have decreased over time while the toxic heavy metal, Cd, has increased, indicating modern wheats are becoming a better vector of dietary Cd.

Stimulatory Effects of Boscalid on Virulence of Sclerotinia sclerotiorum Indicate Hormesis May Be Masked by Inhibitions.

Hormetic effects of fungicides on phytopathogens are of great importance for proper application of fungicides. The aim of the present study was to investigate the stimulatory effects of the fungicide boscalid on mycelial growth and virulence of the devastating plant pathogen Sclerotinia sclerotiorum. Boscalid in potato dextrose agar (PDA) at a dosage range from 0.0005 to 0.002 μg/ml exerted statistically significant (P ≤ 0.015) stimulations on mycelial growth of S. sclerotiorum, and the maximum stimulation magnitudes were 5.55 ± 0.73% (mean ± SD) for the four isolates tested. Boscalid in PDA at 0.02 μg/ml inhibited mycelial growth of isolates HLJ3H and HLJ4H by 15.0 and 8.9%, respectively. However, after the growth-inhibited mycelia were inoculated on rapeseed leaves, isolates HLJ3H and HLJ4H exhibited virulence stimulations of 8.7 and 17.8%, respectively, indicating that hormesis may be masked by inhibitions. Boscalid sprayed at 0.0001 to 0.1 μg/ml on detached rapeseed leaves had significant (P ≤ 0.041) stimulations on virulence of S. sclerotiorum, and the maximum stimulation magnitudes were 17.90 ± 5.94% (mean ± SD) for the four isolates tested. Experiments on 12 isolates with different levels of virulence showed there was a negative correlation (R = -0.663, P = 0.019) between the maximum virulence stimulation magnitude and virulence of S. sclerotiorum in the absence of fungicide. Boscalid at stimulatory concentrations had no significant effect on the expression levels of three virulence-associated genes that encode cutinase (SsCut), polygalacturonase (SsPG1), and oxaloacetate acetylhydrolase (SsOah1). The molecular mechanisms for hormetic effects of boscalid on S. sclerotiorum remain to be studied in the future.

In vivo sensitivity of Phakopsora pachyrhizi to fungicides

ABSTRACT: Asian soybean rust is one of the most destructive diseases that can be found in this crop. It can be largely controlled by fungicide application. The objective was to assess the sensitivity of P. pachyrhizi isolates to fungicides. The tests were performed in a completely randomized design, with six replicates. The sensitivity of twelve isolates to site-specific and multisite fungicides at concentrations of 0.1; 1.0; 10.0, and 100.0 mg L-1, plus a control with absence of fungicide (0.0 mg L-1) was assessed. Soybean leaflets were immersed in the appropriate fungicide solutions, disposed in wet chambers in plastic boxes, and inoculated using each uredinia suspension of P. pachyhrizi (5.0 x 104 uredospores mL-1), separately. Boxes were incubated for 20 days at a temperature of 23°C and a 12-hour photoperiod. Next, the number of uredinia per cm2 on the abaxial face of each leaflet was evaluated. The active ingredients prothioconazole, trifloxystrobin, fluxapiroxade, trifloxystrobin + prothioconazole, trifloxystrobin + bixafen + prothioconazole, azoxystrobin + benzovindiflupyr, and azoxystrobin + benzovindiflupyr + diphenoconazole were highly fungitoxic for the majority of the isolates, with EC50 lower than 1.0 mg L-1. Diphenoconazole, azoxystrobin, and fenpropimorph were considered moderately fungitoxic for nine of the twelve isolates, with EC50 between 1 and 10 mg L-1. The multisites mancozeb and copper oxychloride presented EC50 responses classified as low toxic for the twelve isolates and eight for chlorothalonil (EC50 between 10 mg L-1 and 50 mg L-1). Site-specific fungicides showed high-to-moderate fungitoxicity to P. pachyrhizi isolates, even as the multisites presented moderate-to-less toxic activity.

Assessing Fitness Costs and Phenotypic Instability of Fentin Hydroxide and Tebuconazole Resistance in Venturia effusa

Sensitivity monitoring of Venturia effusa, cause of pecan scab, has revealed insensitivity to fentin hydroxide and tebuconazole, but recent research indicates that the insensitivity to fentin hydroxide is not stable. A study was undertaken to determine if a fitness cost may be responsible for this instability. In this study, experiments were conducted to evaluate fitness components and phenotypic stability of insensitivity of V. effusa to fentin hydroxide and tebuconazole. Conidial production, conidial germination, microcolony growth, sensitivity to osmotic stress, and sensitivity to oxidative stress in the absence of fungicide were compared for isolates with differing sensitivities to both fungicides. Percent conidial germination decreased linearly with increasing fentin hydroxide insensitivity, and microcolony growth on 1.0 mM H2O2 decreased linearly with increasing tebuconazole insensitivity. Stability of resistance was assessed on concentrations of 1.0, 3.0, and 10 µg/ml of both fungicides prior to and after five transfers on non-fungicide-amended medium. Tebuconazole insensitivity was stable after transfers, but fentin hydroxide insensitivity on 1.0 and 3.0 µg/ml decreased significantly after transfers, indicating instability. Here we provide evidence that in V. effusa tebuconazole insensitivity is stable and fentin hydroxide insensitivity is not. These results suggest that fentin-hydroxide-resistant V. effusa isolates have reduced conidial viability compared with sensitive isolates, which may allow the population to regain sensitivity in the absence of this frequently used fungicide.

Management of white mold in common bean using partial resistance and fungicide applications

White mold (WM) is a damaging disease of common bean in Brazil and fungicide applications can effectively control it. However, in the absence of fungicide, some type III bean genotypes have exhibited less WM disease and higher yields under field conditions than the current Brazilian cultivars. Here we assessed the possibility of reducing the number of foliar fungicide applications to control WM using genotypes partially resistant to WM. The production of sclerotia was also assessed. We conducted sprinkler-irrigated trials combining genotypes (susceptible, moderately resistant or partially resistant to WM) with a number of fluazinam applications (0, 1, 2 or 3) under low, low/moderate, moderate or high WM pressure. Under low and low/moderate pressure, one fungicide application reduced WM disease for the susceptible genotype, but did not affect WM disease for the partially resistant genotype. In these conditions, fungicide did not affect yield for either of the genotypes. Under moderate and high pressure and in the cross-site analysis, genotype-by-fungicide interactions were nonsignificant for WM incidence, WM severity index, yield and sclerotia weight. Averaged across site and fungicide, the partially resistant genotype presented a 30% lower WM severity index and produced 2.3-fold fewer sclerotia than the susceptible genotype. We conclude that partially field-resistant beans may contribute to the integrated management of WM, with a potential, at least under light pressure, to reduce the use of fungicide.

Fitness costs associated with G461S mutants of Monilinia fructicola could favor the management of tebuconazole resistance in Brazil

In this study, we investigated the sensitivity components of demethylation fungicide inhibitors (DMI-tebuconazole) for two different sensitivity genotypes of Monilinia fructicola (G461S mutants and wild-type isolates). These components included the fungicide resistance stability and fitness studied over the course of nine and five successive transfers in vitro and ex vivo, respectively, in the absence of fungicide. The results showed no effect of successive transfers on tebuconazole sensitivity of isolates with the G461S mutation for in vitro and ex vivo assays. Athough stable resistance was found, resistant isolates demonstrated a fitness disadvantage relative to the wild-type isolates. The in vitro assay revealed that wild-type isolates had higher germination rates and mycelial growth capacity; and when tested ex vivo, wild-type isolates could produce more spores and larger lesions in peach fruit. The competition studies corroborate the predicted fitness results, where resistant spores were less frequently re-isolated from two pairs of resistant and sensitive mixtures prepared at different ratios. The results obtained in this study have important implications for tebuconazole resistance management of stone-fruit orchards in Brazil and field tests are currently underway to confirm its practicality.

Population Structure of Pseudocercospora fijiensis in Costa Rica Reveals Shared Haplotype Diversity with Southeast Asian Populations

Pseudocercospora fijiensis is the causal pathogen of black Sigatoka, a devastating disease of banana that can cause 20 to 80% yield loss in the absence of fungicides in banana crops. The genetic structure of populations of P. fijiensis in Costa Rica was examined and compared with Honduran and global populations to better understand migration patterns and inform management strategies. In total, 118 isolates of P. fijiensis collected from Costa Rica and Honduras from 2010 to 2014 were analyzed using multilocus genotyping of six loci and compared with a previously published global dataset of populations of P. fijiensis. The Costa Rican and Honduran populations shared haplotype diversity with haplotypes from Southeast Asia, Oceania, and the Americas but not Africa for all but one of the six loci studied. Gene flow and shared haplotype diversity was found in Honduran and Costa Rican populations of the pathogen. The data indicate that the haplotypic diversity observed in Costa Rican populations of P. fijiensis is derived from dispersal from initial outbreak sources in Honduras and admixtures between genetically differentiated sources from Southeast Asia, Oceania, and the Americas.

The Future of Lr34 in Modern, High‐Input Wheat Breeding Programs

Lr34 is an important adult plant resistance gene that is effective against a number of wheat (Triticum aestivum L.) diseases and has proved durable for over 100 yr. However, the energy requirements of Lr34 resistance, combined with the pleiotrophic effect of leaf tip necrosis, can result in reduced yield potential. To evaluate the absence of Lr34 from elite breeding material, a cross was made between similar‐yielding, milling wheat cultivars ‘Conquest’ (Lr34sus) and ‘Bakker Gold’ (Lr34res). Independent lines were carried forward and, at the F4 stage, sister pairs were selected for the different homozygous alleles of the marker csLV34, corresponding to Lr34res or Lr34sus. These lines were further selfed to produce nine stable F8 pairs (Lr34res and Lr34sus) for field trialing and evaluation over 3 yr under a range of fungicide treatments. In the absence of fungicide and with natural infections of stripe rust (Puccinia striiformis f.sp. tritici) and leaf rust (Puccinia triticina), Lr34res lines had lower disease severity, increased total yield, and better grain quality than Lr34sus lines. This pattern was reversed under full fungicide control, as Lr34sus lines displayed higher mean plot yield (2010: +4.3%, p &lt; 0.001; 2012: +4.4%, p &lt; 0.001) and possessed superior grain quality data than the Lr34res lines. The high‐yield, high‐input farming environment and the use of full fungicide control in New Zealand's current wheat cultivar trialing system means that genetic sources of rust resistance such as Lr34 provide little or no competitive advantage.

Demethylase Inhibitor Fungicide Resistance in Pyrenophora teres f. sp. teres Associated with Target Site Modification and Inducible Overexpression of Cyp51.

Pyrenophora teres f. sp. teres is the cause of net form of net blotch (NFNB), an economically important foliar disease in barley (Hordeum vulgare). Net and spot forms of net blotch are widely controlled using site-specific systemic fungicides. Although resistance to succinate dehydrogenase inhibitors and quinone outside inhibitors has been addressed before in net blotches, mechanisms controlling demethylation inhibitor resistance have not yet been reported at the molecular level. Here we report the isolation of strains of NFNB in Australia since 2013 resistant to a range of demethylase inhibitor fungicides. Cyp51A:KO103-A1, an allele with the mutation F489L, corresponding to the archetype F495I in Aspergillus fumigatus, was only present in resistant strains and was correlated with resistance factors to various demethylase inhibitors ranging from 1.1 for epoxiconazole to 31.7 for prochloraz. Structural in silico modeling of the sensitive and resistant CYP51A proteins docked with different demethylase inhibitor fungicides showed how the interaction of F489L within the heme cavity produced a localized constriction of the region adjacent to the docking site that is predicted to result in lower binding affinities. Resistant strains also displayed enhanced induced expression of the two Cyp51A paralogs and of Cyp51B genes. While Cyp51B was found to be constitutively expressed in the absence of fungicide, Cyp51A was only detected at extremely low levels. Under fungicide induction, expression of Cyp51B, Cyp51A2, and Cyp51A1 was shown to be 1.6-, 3,- and 5.3-fold higher, respectively in the resistant isolate compared to the wild type. These increased levels of expression were not supported by changes in the promoters of any of the three genes. The implications of these findings on demethylase inhibitor activity will require current net blotch management strategies to be reconsidered in order to avoid the development of further resistance and preserve the lifespan of fungicides in use.

Metabolic effects of azoxystrobin and kresoxim-methyl against Fusarium kyushuense examined using the Biolog FF MicroPlate

Azoxystrobin and kresoxim-methyl are strobilurin fungicides, and are effective in controlling many plant diseases, including Fusarium wilt. The mode of action of this kind of chemical is inhibition of respiration. This research investigated the sensitivities of Fusarium kyushuense to azoxystrobin and kresoxim-methyl, and to the alternative oxidase inhibitor salicylhydroxamic acid (SHAM). The Biolog FF MicroPlate is designed to examine substrate utilization and metabolic profiling of micro-organisms, and was used here to study the activity of azoxystrobin, kresoxim-methyl and SHAM against F. kyushuense. Results presented that azoxystrobin and kresoxim-methyl strongly inhibited conidial germination and mycelial growth of F. kyushuense, with EC50 values of 1.60 and 1.79μgml−1, and 6.25 and 11.43μgml−1, respectively; while not for SHAM. In the absence of fungicide, F. kyushuense was able to metabolize 91.6% of the tested carbon substrates, including 69 effectively and 18 moderately. SHAM did not inhibit carbon substrate utilization. Under the selective pressure of azoxystrobin and kresoxim-methyl during mycelial growth (up to 100μgml−1) and conidial germination (up to 10μgml−1), F. kyushuense was unable to metabolize many substrates in the Biolog FF MicroPlate; while especially for carbon substrates in glycolysis and tricarboxylic acid cycle, with notable exceptions such as β-hydroxybutyric acid, y-hydroxybutyric acid, α-ketoglutaric acid, α-d-glucose-1-phosphate, d-saccharic acid and succinic acid in the mycelial growth stage, and β-hydroxybutyric acid, y-hydroxybutyric acid, α-ketoglutaric acid, tween-80, arbutin, dextrin, glycerol and glycogen in the conidial germination stage. This is a new finding for some effect of azoxystrobin and kresoxim-methyl on carbon substrate utilization related to glycolysis and tricarboxylic acid cycle and other carbons, and may lead to future applications of Biolog FF MicroPlate for metabolic effects of other fungicides and other fungi, as well as providing a carbon metabolic fingerprint of F. kyushuense that could be useful for identification.

Adaptability and Stability of Yield and Industrial Grain Quality with and without Fungicide in Brazilian Oat Cultivars

The use of productive cultivars with adaptability and stability and less demanding to fungicide use are critical to the sustainability of production factors. The objective of this work was to determine the per se performance of white oat cultivars and parameters of adaptability and stability on yield and grain quality in the proposition of cultivars more responsive in reducing the use fungicide. The study was conducted in Augusto Pestana, RS, Brazil, between the years 2010 and 2013. The experimental design was randomized blocks with six replicates, three with and three without fungicide. The study evaluated 14 white oat cultivars for yield and industrial capability. The white oat cultivars FAEM 4 Carlasul and URS Corona indicate high grain yield with stability and general adaptability, independent of chemical control. The cultivar URS Corona shows together high yield and thousand grain weight and hectoliter with general adaptability and stability in the absence of fungicide. Although no stability has been detected in industrial yield without the use of fungicides, cultivars of URS Charrua, URS Corona and URS Taura show high means with general adaptability.

Eficiência de fungicidas no controle da brusone em trigo

Causada pelo fungo Pyricularia grisea, a brusone do trigo constitui-se num dos principais entraves à expansão da produção tritícola no Brasil Central. O objetivo deste trabalho foi avaliar a eficiência de fungicidas no controle da brusone em trigo. Foram utilizados três fungicidas, com princípios ativos distintos, combinados com quatro genótipos de trigo. Realizaram-se duas aplicações do produto comercial, sendo estas no estádio 45 e 65 da escala de Zadokset al. A inoculação artificial com os esporos de P. grisea ocorreu no estádio 58-60 da referida escala. Determinou-se a área abaixo da curva de progresso da doença (AACPD), a severidade em folhas bandeira (SEVFB) e em espigas (SEVEsp) e quantificou-se a produção de grãos (PG).Ao final do trabalho, os diferentes parâmetros analisados foram submetidos à análise de correlação de Pearson.Os fungicidas epoxiconazol+piraclostrobina e tebuconazol+trifloxistrobina foram os que proporcionaram menor AACPD nos genótipos VI 03061, VI 07505 e BRS 254. Não houve diferença para SEVFB entre os genótipos na presença de fungicidas. As linhagens VI 98053 e VI 07505 apresentam menor SEVFB na ausência de fungicidas.O fungicida tebuconazole+trifloxistrobina proporcionou maior PG e menor SEVEsp. A severidade da doença em espigas foi maior do que em folhas bandeira. O controle da brusoneem trigo através da aplicação de fungicidas mostrou-se eficiente em folhas bandeira, mas não eficiente para o controle nas espigas.

Development of a semi-selective medium for improved isolation of the turfgrass dollar spot pathogen Sclerotinia homoeocarpa from host tissues

Dollar spot, caused by Sclerotinia homoeocarpa, is one of the most economically devastating diseases of amenity turfgrasses worldwide. The pathogen is readily isolated from active lesions, but detection from seed, dormant host tissue and other plant debris that may serve as a source of primary inoculum is difficult. A semi-selective medium was developed to enhance isolation of S. homoeocarpa. Various fungicides used on turfgrass, the pH indicator dye bromophenol blue, and two pH levels, were assessed for their effects on, and in the case of bromophenol blue, response to growth of S. homoeocarpa and contaminant fungi frequently isolated from field and seed samples. Amendment of the medium to pH 4 promoted growth of S. homoeocarpa in the absence of fungicides and enhanced pathogen growth relative to contaminant isolates on medium amended with 0.1 μg mL−1 triticonazole or 5 μg mL−1 azoxystrobin. The growth rate of S. homoeocarpa on these three media, as determined by in vitro radial growth assays, was consistent for many isolates representing the majority of S. homoeocarpa vegetative compatibility groups. Isolation efficiency on the pH-amended media was tested against antibiotic-amended potato dextrose agar from field samples and artificially inoculated turfgrass seed. In both cases, the medium amended to pH 4 and containing 5 μg mL−1 azoxystrobin significantly decreased contaminant growth with no adverse effects on recovery of S. homoeocarpa in comparison with antibiotic-amended PDA. The enhanced specificity of this medium will be a useful tool for selective detection of S. homoeocarpa and identification of sources of initial inoculum for dollar spot development.