ABSTRACT The effects of different nitrogen doses on dry weight yield, stevioside and rebaudioside A contents, and yields were evaluated in stevia (Stevia rebaudiana Bertoni). This study was carried out at the Instituto Federal Catarinense, Rio do Sul (SC), Brazil, under decreasing photoperiods. A randomized complete block design with four blocks and five treatments (0, 65, 135, 200 and 270 kg ha-1 N) was used. Variables related to dry weight yield (total dry weight, leaf dry weight, stem dry weight, number of secondary branches and tertiary branches, and main stem length), growth rates (total leaf area, leaf area index, specific leaf area, leaf area ratio, leaf weight ratio), and stevioside and rebaudioside A contents and yields were evaluated. The doses of nitrogen fertilization did not affect the variables related to dry weight yield, stevioside and rebaudioside A contents and yields, or rebaudioside A:stevioside ratio in stevia genotype 8 (G8), grown under decreasing photoperiods.

RESUMEN El efecto de diferentes tasas de nitrógeno en la producción de biomasa, el contenido y rendimiento de esteviósido y rebaudiósido A en el cultivo de estevia se evaluaron en un experimento de campo en el Instituto Federal Catarinense, Rio do Sul (SC), Brasil, en condiciones de fotoperíodo decreciente. Se utilizó un diseño de bloques completos al azar con cuatro bloques y cinco tratamientos (0, 65, 135, 200 y 270 kg ha-1 N). Se evaluaron las variables relacionadas con la producción de biomasa (DM total, tallo MS, hojas MS, número de ramas secundarias, número de ramas terciarias y longitud de rama más grande), variables relacionadas con los índices de crecimiento (AFT, IAF, AFE, RAF y RPF) y también variables relacionadas con el contenido y el rendimiento de esteviósido y rebaudiósido A. Las diferentes dosis de fertilización nitrogenada no afectaron las variables relacionadas con la acumulación de materia seca en el genotipo G8 cultivado en condiciones de fotoperíodo decreciente en las condiciones de campo. Los niveles de fertilización nitrogenada no afectaron los niveles de esteviósido y rebaudiósido A, la productividad de esteviósido y rebaudiósido A y la proporción de rebaudiósido A / esteviósido en el G8 cultivado en condiciones de fotoperíodo de disminución de campo.

RESUMO O míldio da cebola causado por Peronospora destructor exige pulverização semanal de fungicidas para seu controle e com intuito de reduzir esse número, o presente trabalho teve como objetivo avaliar tecnicamente e economicamente um sistema de previsão da doença e comparar com o sistema convencional de controle. Um experimento em blocos casualizados com quatro repetições e quatro tratamentos foi instalado em 2018 e 2019 em Rio do Sul (SC) com o cultivar de cebola Empasc 352 – Bola Precoce. No sistema convencional, as pulverizações iniciaram uma semana após o transplantio e semanalmente durante o ciclo da cultura com um tratamento utilizando fungicida protetor e outro com sistêmico e no sistema de previsão foi realizado após 30 dias utilizando o sistema validado por Marcuzzo quando o valor de severidade da doença (VDS) atingisse doze pontos utilizando os mesmos tipos de fungicidas do convencional em cada tratamento. No sistema de previsão com protetor se ocorresse um acúmulo de chuva de 25mm de chuva era feito a reaplicação do fungicida. A área abaixo da curva de progresso da doença, severidade final e a taxa de progresso da doença e a produtividade não diferiram entre os tratamentos, mas no sistema de previsão com fungicida protetor a redução do número de pulverizações foi de 31 e 43% menor em relação ao sistema de aplicação semanal respectivamente em 2018 e 2019, enquanto que o sistêmico foi de 62% para ambos as safras. O sistema de previsão possibilitou uma redução de custo com fungicida sistêmico de R$ 3.000,00 e 3.500,00/ha para os respectivos anos em comparação ao convencional, enquanto que o protetor foi de R$ 210,00 e 480,00/ha para 2018 e 2019 respectivamente. O uso do sistema de previsão mostrou ser uma ferramenta viável no manejo do míldio da cebola no estado de Santa Catarina e encontra-se disponível para a cadeia produtiva em http://www.ciram.sc.gov.br/agroconnect/.

ABSTRACT Onion downy mildew caused by tlid-translationPeronospora destructortlid-translation requires weekly spraying of fungicides for its control and, in order to reduce this number, the present study aimed to technically and economically evaluate a disease forecasting system and compare it with the conventional control system. A randomized block design with four replicates and four treatments was established in 2018 and 2019 in Rio do Sul City (Santa Catarina State, Brazil) with the onion cultivar Empasc 352 - Bola Precoce. For the conventional system, spraying started one week after transplanting and was weekly performed during the crop cycle with a treatment using protective fungicide and another treatment using systemic fungicide. For the forecasting system, spraying was performed after 30 days, adopting the system validated by Marcuzzo, when the disease severity value (DSV) reached twelve points and the same types of fungicides used in the conventional system for each treatment. The forecasting system had the protective fungicide reapplied when accumulated rainfall was 25mm. Area under the disease progress curve, final severity, disease progression rate and yield did not differ between treatments, but the reduction in the number of sprays for the protective fungicide in the forecasting system was 31% and 43% smaller than that in the weekly application system in 2018 and 2019, respectively, while such a reduction was 62% for the systemic fungicide in both years. The forecasting system allowed a reduction in the cost with systemic fungicide of R$ 3,000.00 and R$ 3,500.00/ha for the respective years, compared to the conventional system, while with the protective fungicide the cost reduction was R$ 210.00 and 480.00/ha for 2018 and 2019, respectively. The forecasting system has proven to be a viable tool for the management of onion downy mildew in Santa Catarina State, Brazil, and is available for the production chain at http://www.ciram.sc.gov.br/agroconnect/.

RESUMEN La evaluación de cuatro genotipos de estevia para la producción de biomasa, el contenido y rendimiento de esteviósido y rebaudiósido A, se llevó a cabo en la región de Alto Vale do Itajaí, estado de Santa Catarina, SC (Brasil), en condiciones de disminución de fotoperíodo. El experimento se realizó en el campo de la Granja São Miguel, Lontras, SC, Brasil, bajo condiciones de disminución del fotoperíodo, con una variación de 13.72 h de luz, en el momento de la implantación del experimento, a 12.57 h de luz al final de las evaluaciones. Los tratamientos fueron cuatro genotipos (G4, G8, G9 y G12), procedentes de EMBRAPA-CENARGEN. Se utilizó un diseño de bloques completos al azar con cuatro tratamientos (genotipos de estevia) y cuatro repeticiones. Cada parcela constaba de 21 plantas y el área del piso por cinco plantas. G12 tuvo el mayor peso seco de la hoja (PSH), área foliar total, índice de área foliar, relación de área foliar y área foliar específica de todos los genotipos. G4 y G12 presentaron similitud en PSH, siendo superiores a los demás, con producción de 755,6 y 836,4 kg ha-1, respectivamente. El contenido de esteviósido fue mayor en G12 (200.07 mg g-1). G8 y G9 fueron iguales para el contenido de rebaudiósido A, presentando 64,77 y 49,05 mg g-1, respectivamente. La relación rebaudiósido A: esteviósido fue mayor en el genotipo G8 (0,44 g g-1). Ningún genotipo evaluado bajo las condiciones productivas del Alto Vale do Itajaí presentó la relación rebaudiósido A: esteviósido apropiada requerido para la industria.

ABSTRACT An evaluation of four stevia genotypes for biomass yield, stevioside and rebaudioside A content and yield under decreasing photoperiod conditions was carried out in the Alto Vale do Itajaí region, located in the State of Santa Catarina (SC), Brazil. This field experiment was conducted at Site São Miguel, a farm located in the city of Lontras (SC), Brazil, under conditions of decreasing photoperiods, with a variation of 13.72 h of light at experiment implantation to 12.57 h of light at the end of the evaluations. The treatments consisted of four genotypes (G4, G8, G9 and G12) provided by EMBRAPA-CENARGEN. A randomized complete block design with four treatments (stevia genotypes) and four replications was used. Each plot consisted of 21 plants, and the floor area had five plants. G12 had the highest leaf dry weight (LDW), total leaf area, leaf area index, leaf area ratio and specific leaf area of all the genotypes. G4 and G12 were equal for LDW and were higher than the other genotypes, with yields of 755.6 and 836.4 kg ha-1, respectively. The stevioside content was highest in G12 (200.07 mg g-1). G8 and G9 were similar for rebaudioside A content (64.77 and 49.05 mg g-1, respectively). The rebaudioside A: stevioside ratio was highest in G8 (0.44 g g-1). No genotype had a rebaudioside A: stevioside ratio suitable for industry requirements.