Padronização de métodos para inoculação de Sporisorium scitamineum em testes de resistência ao carvão da cana-de-açúcar
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2016-05-30
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Universidade Estadual Paulista (Unesp)
Resumo
O carvão da cana-de-açúcar (Sporisorium scitamineum) é uma das principais doenças que causam perda na produtividade e redução do estande da cultura. Não há até o momento, metodologias adequadas e genótipos que possam contribuir à discriminação dos materiais genéticos quanto aos níveis de resistência de forma convincente e segura. Com isso, os objetivos do presente trabalho foram: (i) determinar metodologias mais adequadas de inoculação e de pós-inoculação; (ii) avaliar o comportamento diferencial de genótipos de cana-de-açúcar quando submetidos a diferentes métodos de inoculação; (iii) padronizar metodologias de avaliação do carvão empregando-se métodos de inoculação, temperatura pós-inoculação, e padrões de suscetibilidade, intermediário e resistência para programas de melhoramento. Foram realizados três experimentos, em diferentes épocas, conduzidos em cana-planta e cana-soca, em casa de vegetação e a campo. No primeiro experimento, foram avaliadas as condições ideais prévias de inoculação e de pós-inoculação, empregando os genótipos RB925345 e IACSP03-4080. Os minitoletes de gema individualizada foram inoculados por aspersão, imersão e punctura das gemas com suspensão de 106 teliósporos/mL e posteriormente submetidos a temperaturas de 26, 28 e 30°C por 72 horas. Foi empregado o delineamento inteiramente casualizado com quatro repetições em cana-planta por 180 dias, e em cana-soca por 180 dias em casa de vegetação. A avaliação consistiu na determinação semanal da incidência de plantas com chicote. Posteriormente, os genótipos Co419, NA56-79, RB925345, SP80-3280, IACSP93-3046, IACSP95-5000, IACSP95-5094, IACSP96-2042, IACSP96-3060, IACSP96-7569, IACSP96-3076, IACSP97-4039, IACSP98-2053, IACSP03-4080, foram submetidos aos métodos de inoculação por aspersão, imersão e punctura em suspensão de mesma concentração de teliósporos já descrita. O delineamento foi inteiramente casualizado em cana-planta conduzido em casa de vegetação e em blocos casualizados em cana-soca conduzida à campo. As avaliações da incidência de plantas com chicotes foram realizadas semanalmente, em casa de vegetação, durante 180 dias em cana-planta, e por mais 180 dias em cana-soca em campo. Um terceiro experimento foi realizado, utilizando os genótipos Co419, NA56-79, SP80-3280, IACSP93-3046, IACSP95-5094 e IACSP03-4080, com a intenção de validação dos resultados obtidos para padronização da metodologia de inoculação e pós-inoculação e genótipos. O experimento foi conduzido a campo por 180 dias, sendo avaliado quanto a incidência de carvão. Os resultados revelam que a temperatura ideal pós-inoculação foi de 28°C por demonstrar melhor resposta quanto à porcentagem de brotação das gemas e incidência de plantas com chicotes. O melhor método indicado para as fases de seleções de genótipos resistentes foi inoculação por imersão, por ser mais próximo das condições naturais. Já o método por punctura pode ser indicado para identificar genitores resistentes a serem utilizados em cruzamentos genéticos, por ser um método mais agressivo, possibilitando a obtenção de genótipos resistentes geneticamente. O método de aspersão mostrou-se pouco viável devido às possíveis falhas de inoculação. Experimentos conduzidos a campo revelaram resultados mais rápidos e seguros, em relação aos conduzidos em casa de vegetação. A nova escala de avaliação proposta neste trabalho permitiu melhores condições para caracterização dos genótipos quanto à resistência ao carvão e respostas em menor tempo de avaliação. Os genótipos Co419, IACSP03-4080 e IACSP93-3046 mostraram-se adequados como padrões de suscetibilidade; NA56-79 intermediário e SP80-3280 de resistência.
Smut of sugarcane (Sporisorium scitamineum) is one of the main diseases that cause loss of productivity and crop stand reduction. There are still no appropriate methodologies and genotypes that could contribute to the discrimination of genetic material and the resistance levels in a convincing and safe way. Thus, this study aimed: (i) determine the most appropriate methods of inoculation and pos inoculation; (ii) evaluate the behavior of sugarcane genotypes when submitted to different methods of inoculation; (iii) standardize assessment methodologies for smut, employing methods of inoculation, pos inoculation temperature, and susceptibility patterns, intermediate and resistance to breeding programs. Three experiments were carried out at different times, using cane plant and ratoon cane in greenhouse and field. In the first experiment, the ideal preconditions for inoculation and pos inoculation were evaluated using the RB925345 and IACSP03-4080 genotypes. The individualized bud setts were inoculated by spraying, immersion and puncture (wounding) of the buds with teliospore suspension of 106/mL and then subjected to temperatures of 26, 28 and 30°C for 72 hours. It was used a completely randomized design with four replications in cane plant for 180 days, and in ratoon cane /for 180 days in a greenhouse. The evaluation consisted of weekly determination of the incidence of plants with whip. Subsequently, Co419, NA56-79, RB925345, SP80-3280, IACSP93-3046, IACSP95-5000, IACSP95-5094, IACSP96-2042, IACSP96-3060, IACSP96-7569, IACSP96-3076, IACSP97-4039, IACSP98-2053, IACSP03-4080 genotypes underwent methods of inoculation by spraying, immersion and puncture suspension of same concentration of teliospores already described. The design was completely randomized in cane plant carried out in a greenhouse and a randomized block of ratoon under field conditions. Evaluations of whips incidence in plants were done weekly, in a greenhouse, 180 days in cane plant, and for another 180 days in ratoon at field. A third experiment was carried out using the Co419, NA56-79, SP80-3280, IACSP93-3046, IACSP95-5094 and IACSP03-4080 genotypes with the intention to validate the results obtained to standardize the methodology of inoculation and pos inoculation and genotypes. The experiment was carried out under field conditions for 180 days and the whip incidence was evaluated. The results show that pos inoculation optimal temperature was 28°C due to demonstrate better response as the buds sprouted percentage and incidence of plants with whips. The best method suitable for screening for smut resistance resistant genotypes phase selections was the inoculation by immersion, closer to the natural conditions. The puncture method can be indicated to identify parents resistant in genetic crosses, due to be a more aggressive method, enabling the production of genotypes genetically resistant. The spray method was impractical because of the possible inoculation failures. The experiments carried out under field conditions revealed faster and safe results related to the ones conducted in the greenhouse. This work new scale proposed evaluation enabled better conditions to characterize genotypes for smut resistance as well as faster evaluation answers. The IACSP03-4080, Co419 and IACSP93-3046 genotypes proved to be suitable as susceptibility patterns; NA56-79 intermediate and SP80-3280 resistance.
Smut of sugarcane (Sporisorium scitamineum) is one of the main diseases that cause loss of productivity and crop stand reduction. There are still no appropriate methodologies and genotypes that could contribute to the discrimination of genetic material and the resistance levels in a convincing and safe way. Thus, this study aimed: (i) determine the most appropriate methods of inoculation and pos inoculation; (ii) evaluate the behavior of sugarcane genotypes when submitted to different methods of inoculation; (iii) standardize assessment methodologies for smut, employing methods of inoculation, pos inoculation temperature, and susceptibility patterns, intermediate and resistance to breeding programs. Three experiments were carried out at different times, using cane plant and ratoon cane in greenhouse and field. In the first experiment, the ideal preconditions for inoculation and pos inoculation were evaluated using the RB925345 and IACSP03-4080 genotypes. The individualized bud setts were inoculated by spraying, immersion and puncture (wounding) of the buds with teliospore suspension of 106/mL and then subjected to temperatures of 26, 28 and 30°C for 72 hours. It was used a completely randomized design with four replications in cane plant for 180 days, and in ratoon cane /for 180 days in a greenhouse. The evaluation consisted of weekly determination of the incidence of plants with whip. Subsequently, Co419, NA56-79, RB925345, SP80-3280, IACSP93-3046, IACSP95-5000, IACSP95-5094, IACSP96-2042, IACSP96-3060, IACSP96-7569, IACSP96-3076, IACSP97-4039, IACSP98-2053, IACSP03-4080 genotypes underwent methods of inoculation by spraying, immersion and puncture suspension of same concentration of teliospores already described. The design was completely randomized in cane plant carried out in a greenhouse and a randomized block of ratoon under field conditions. Evaluations of whips incidence in plants were done weekly, in a greenhouse, 180 days in cane plant, and for another 180 days in ratoon at field. A third experiment was carried out using the Co419, NA56-79, SP80-3280, IACSP93-3046, IACSP95-5094 and IACSP03-4080 genotypes with the intention to validate the results obtained to standardize the methodology of inoculation and pos inoculation and genotypes. The experiment was carried out under field conditions for 180 days and the whip incidence was evaluated. The results show that pos inoculation optimal temperature was 28°C due to demonstrate better response as the buds sprouted percentage and incidence of plants with whips. The best method suitable for screening for smut resistance resistant genotypes phase selections was the inoculation by immersion, closer to the natural conditions. The puncture method can be indicated to identify parents resistant in genetic crosses, due to be a more aggressive method, enabling the production of genotypes genetically resistant. The spray method was impractical because of the possible inoculation failures. The experiments carried out under field conditions revealed faster and safe results related to the ones conducted in the greenhouse. This work new scale proposed evaluation enabled better conditions to characterize genotypes for smut resistance as well as faster evaluation answers. The IACSP03-4080, Co419 and IACSP93-3046 genotypes proved to be suitable as susceptibility patterns; NA56-79 intermediate and SP80-3280 resistance.
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Palavras-chave
Resistência varietal, Saccharum spp., Temperatura pós-inoculação, Varietal resistance, Pos inoculation temperature