Wheat blast, caused by Pyricularia oryzae Triticum (PoT) lineage, is a major constraint to wheat production, mainly in the tropics of Brazil where severe epidemics are more frequent. We analyzed disease and wheat yield data from 42 uniform field trials conducted during nine years (2012 to 2020) in order to assess whether the percent control and yield response were influenced by fungicide type, region (tropical or subtropical), and year. Six treatments were selected, all evaluated in at least 19 trials. Two fungicides were applied as solo active ingredients: MANCozeb, and TEBUconazole, and four were premixes: AZOXystrobin + TEBU, TriFLoXystrobin + PROThioconazole, TFLX + TEBU, and PYRAclostrobin + EPOXiconazole. Percent control, calculated from back-transforming estimates by a meta-analysis network model fitted to the log of the means, ranged from 43% to 58%, with all but PYRA + EPOX showing efficacy greater than 52% on average, not differing among them. The variation in both efficacy and yield response was explained by region and all but TEBU performed better in the subtropics than in the tropics. Yield response from using three sequential sprays was around two times greater in the subtropics (319 to 532 kg/ha) than in the tropics (149 to 241.3 kg/ha). No significant decline in fungicide efficacy or yield response was observed in nine years of study for any of the fungicides. Our results reinforce the need to improve control by adopting an integrated management approach in the tropics given the poorer performance and lower profitability, especially for the premixes, than in the subtropics.
Fusarium head blight (FHB), caused mainly by Fusarium graminearum, is best controlled with demethylation inhibitor (DMI) fungicides during flowering. However, the use of premixes of DMI and quinone outside inhibitor (QoI) fungicides to control FHB has increased in Brazil. Data on FHB severity and wheat yields measured in field experiments conducted in Brazil were gathered from both peer- and non-peer-reviewed sources published from 2000 to 2018. After applying selection criteria, 73 field trials from 35 bibliographic sources were identified, among which 50% of the data were obtained from cooperative network trials conducted after 2011. To be included in the analysis, a DMI+QoI premixes or tebuconazole (TEB) were tested in at least 14 trials and three years. Four premixes met the criteria. Estimates of percent control (and respective 95% confidence interval) by a network model fitted to the log of the treatment means ranged from 44.1% (pyraclostrobin + metconazole applied once; 32.4 to 53.7) to 64.3% (pyraclostrobin + metconazole; 58.4 to 69.3); the latter not differing from TEB (59.9%, 53.6 to 65.3). Yield response was statistically similar for pyraclostrobin + metconazole (532.1 kg/ha, 441 to 623) and trifloxystrobin + prothioconazole (494.9 kg/ha, 385 to 551), and both differed statistically from a group composed of TEB (448.2 kg/ha, 342 to 554), trifloxystrobin + TEB (468.2 kg/ha, 385 to 551), azoxystrobin + TEB (462.4 kg/ha, 366 to 558) and pyraclostrobin + metconazole applied once (413.7 kg/ha, 308 to 518). The two categories of FHB index (7% cut off) and yield (3,000 kg/ha cut off), both in the non-treated check, did not explain the heterogeneity in the estimates. Two sequential sprays of TEB or one spray of pyraclostrobin + metconazole as management choices are likely more profitable than DIM+QoI premixes sprayed twice during flowering considering only the fungicide effects on yield.
-The Brazilian pastures establishment success depends on the use of seeds with high physiological and sanitary quality. The aim of this study was to evaluate the effect of thermal and chemical treatments on quality of Brachiaria brizantha, cv. BRS Piatã and pathogen transmission via seed. The treatments included the use of fungicides, detergent, sodium hypochlorite, sulfuric acid and alcohol, as well as thermal treatments. In addition to seeds without treatment, nine treatments were tested.The tests used to assess the physiological quality of the seeds were first and final count of germination test and root protrusion; germination and root protrusion speed index. A transmitting test and filter paper method had been performed for sanitary quality. Fungal lower incidence was observed in seeds treated with alcohol, however, this treatment reduced the physiological quality of the seeds and higher frequency of fungi transmission from seeds to seedlings was observed for Bipolaris sp., Fusarium sp. and Phoma sp. Treatment with sulfuric acid provided a better seed germination performance and reduced the incidence of fungi.Index terms: germination, vigor, seed-seedling, incidence, forage.Qualidade fisiológica, sanitária e transmissão de fungos associados às sementes de Brachiaria brizantha (Hochst. ex. A. Rich.) Stapf submetidas a tratamentos térmicos e químicos RESUMO -O sucesso no estabelecimento das pastagens brasileiras depende da utilização de sementes com boa qualidade fisiológica e sanitária. Objetivou-se com o trabalho avaliar o efeito de tratamentos térmicos e químicos sobre a qualidade fisiológica e sanitária de sementes de Brachiaria brizantha, cultivar BRS Piatã e a transmissão de patógenos via semente. Os tratamentos incluíram o uso de fungicidas, detergente, hipoclorito de sódio, álcool e ácido sulfúrico, além de tratamentos térmicos. Os testes utilizados para a avaliação da qualidade fisiológica das sementes foram primeira contagem e contagem final do teste de germinação e de protrusão radicular; índice de velocidade de germinação e de protrusão radicular. Para a qualidade sanitária foi realizado o método de papel de filtro e o teste de transmissão. Menor incidência fúngica foi observada nas sementes tratadas com álcool, no entanto, esse tratamento reduziu a qualidade fisiológica das sementes e maior frequência de transmissão de fungos das sementes para as plântulas foi observada para Bipolaris sp., Fusarium sp. e Phoma sp. O tratamento com ácido sulfúrico proporcionou melhor desempenho germinativo das sementes e reduziu a incidência de fungos.Termos para indexação: germinação, vigor, semente-plântula, incidência, forrageira.
A triticultura brasileira apresenta constantes perdas no rendimento, associadas à ocorrência da ferrugem da folha, causada pelo fungo Puccinia triticina. A incorporação da resistência genética e o conhecimento do número de genes envolvidos são importantes para os programas de melhoramento genético vegetal, que a cada ano têm introduzido resistência qualitativa nas cultivares, visando superar o aparecimento de novas raças do patógeno. As técnicas bioquímicas, baseadas na análise de polimorfismo de enzimas, possibilitam a rápida e precisa detecção de marcadores moleculares, para o estudo de aspectos básicos de genética vegetal, bem como representam valiosa ferramenta de apoio aos programas de melhoramento, pois permitem a identificação antecipada de genótipos resistentes e suscetíveis. Este trabalho visa avaliar, fitopatológica e molecularmente, a população haplodiplóide Trigo BR 35 (resistente)/IAC 13-Lorena (suscetível) de trigo (Triticum aestivum), quanto à resistência de planta adulta à ferrugem da folha, bem como à similaridade genética presente na progênie haplodiploidizada na geração F1. Nas avaliações fitopatológicas em planta adulta, das 96 linhas duplo-haplóide, 29 foram resistentes, 15 suscetíveis e 52 intermediárias apresentaram reação que variou entre nível de resistência inferior ao determinado para Trigo BR 35 a menos suscetível do que IAC 13-Lorena. A análise genética revelou dois genes parcialmente dominantes. Na análise bioquímica, através do sistema isoenzimático das esterases, foram detectadas, seis bandas, todas anódicas e com especificidade alfa-esterásica, cujas MRs (migração relativa) variaram de 0,09 a 0,69. Quanto à variabilidade genética, foi detectada, para as 96 linhas, elevada similaridade genética, a qual confirmou as análises isoesterásicas.
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