Dinâmica e ação do nicosulfuron em híbridos de milho
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Data
2019-03-01
Autores
Bevilaqua, Natalia da Cunha
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Universidade Estadual Paulista (Unesp)
Resumo
O herbicida nicosulfuron se destaca entre os principais utilizados em pós-emergência na cultura do milho. Dentre as tecnologias disponíveis no mercado, alguns híbridos podem ser considerados tolerantes ao nicosulfuron, e essa sensibilidade diferencial está relacionada com o ambiente, o estádio de desenvolvimento da planta e a dose de herbicida utilizada. A seletividade de herbicidas é geralmente determinada em função da fitointoxicação e do efeito do produto nas características morfológicas e fisiológicas das plantas. De modo que o objetivo do trabalho foi determinar a sensibilidade de híbridos de milho ao herbicida nicosulfuron por meio de marcadores bioquímicos. O primeiro experimento foi conduzido em casa-de-vegetação com delineamento experimental inteiramente casualizado com 4 repetições em esquema fatorial 4 x 2 (híbridos x doses), o herbicida foi aplicado nas doses 0 e 120 g i.a. ha-1 quando as plantas se encontravam no estádio fenológico V3. Foram realizadas avaliações da taxa de transporte de elétrons (ETR), fitointoxicação e altura aos 1, 3, 7 e 14 dias após a aplicação (DAA). Aos 14 DAA as plantas foram coletadas para determinação da massa seca. Dentre os híbridos utilizados selecionou-se o mais sensível e o mais tolerante para a realização de análises de determinação dos teores do ácido aminobutírico, e dos aminoácidos valina, leucina e isoleucina, nesses mesmos períodos de avaliação. O segundo experimento foi disposto em delineamento inteiramente casualizado com 5 repetições em esquema fatorial 8 x 2 (híbridos x doses), as doses de nicosulfuron aplicadas foram 0 e 120 g i.a. ha-1. O experimento foi realizado em épocas distintas para os estádios V2 e V6 de desenvolvimento do milho. Um dia após a aplicação do herbicida as plantas foram coletadas para determinação dos teores de nicosulfuron, dos ácidos aminobutírico e quínico e dos aminoácidos valina, leucina e isoleucina. Durante o experimento foram realizadas avaliações da taxa de transporte de elétrons aos 1, 7, 10, 14, 21 e 28 DAA; altura e fitointoxicação das plantas aos 7, 14, 21 e 28 DAA e aos 7 DAA foram determinados os teores de clorofila. As plantas foram coletadas aos 28 DAA para determinação da massa seca da parte aérea. No primeiro experimento, a coleta das plantas um dia após aplicação de nicosulfuron foi considerado o melhor período para determinação dos teores de ácido aminobutírico, uma vez que o maior acúmulo desse composto ocorreu nesse período. O híbrido mais sensível apresentou maiores valores de fitotoxicidade, menores valores de altura, ETR, massa seca e maior acúmulo do ácido aminobutírico quando comparado ao híbrido mais tolerante. No segundo experimento os oito híbridos estudados apresentaram diferentes níveis de sensibilidade ao nicosulfuron e os maiores teores internos e externos do herbicida foram encontrados nas plantas aplicadas no estádio fenológico V2. O acúmulo de aminobutírico nas plantas após aplicação do herbicida ocorreu para todos os híbridos nos dois estádios fenológicos, no entanto só foi possível estabelecer correlações entre o acúmulo de aminobutírico e a sensibilidade dos híbridos quando a aplicação ocorreu no estádio V2 de desenvolvimento das plantas.
Nicosulfuron stands out among the principal post-emergent herbicides used in the maize crop. Among the commercial technologies available, there are some hybrids considered tolerant to this molecule and can present a differential sensitivity, process which is related to the environment, growth stage and herbicide dose. The objective of the study was to determine the sensitivity of corn hybrids to the herbicide nicosulfuron by means of biochemical markers. The first experiment was carried out under greenhouse conditions in a completely randomized design with four replications in a factorial scheme 4 x 2 (hybrids x doses). The herbicide was applied at 0 and 120 g a.i. ha-1, when the plants were in the V3 stage. Electron transport rate (ETR), phytointoxication and plant height were evaluated at 1, 3, 7 and 14 days after treatment (DAT). Plants were collected at 14 DAT to determine its dry weight. The most sensitive and tolerant hybrids were selected to determinate the content of 2-aminobutyric acid and valine, leucine and isoleucine amino acids, in the same evaluation period. The second experiment was arranged in a completely randomized design with five replications in a factorial scheme 8 x 2 (hybrids x doses), the nicosulfuron was applied at 0 and 120 g a.i. ha-1. The experiment was conducted in different periods, for V2 and V6 maize growing stage. One day after the herbicide application, the plants were collected to determine the content of nicosulfuron, 2-aminobutyric and quinic acid, as well as valine, leucine and isoleucine amino acids. During the experiment, the ETR was evaluated at 1, 7, 10, 14, 21 and 28 DAT, and the variables plant height and phytointoxication at 7, 14, 21 and 28 DAT. At 7 DAT the chlorophyll content was determined. Plants were collected at 28 DAT to determine the shoot dry weight. In the first experiment, the collection of the plants one day after application was considered the best period for determination of aminobutyric acid contents, since the greatest accumulation of this compound occurred during that period. The most sensitive hybrid presented higher phytotoxicity values, lower plant height, ETR, dry weight and the highest 2-aminobutyric acid accumulation when compared to the most tolerant hybrid. In the second experiment the eight hybrids presented different sensitivity levels to nicosulfuron. The greatest internal and external herbicide content was observed in V2 stage. The accumulation of 2-aminobutyric acid in the plants after herbicide application occurred for all hybrids in both growing stages, however it was only possible to establish correlations between the accumulation of 2-aminobutyric acid and the sensitivity of the hybrids when the herbicide was applied in the V2 stage.
Nicosulfuron stands out among the principal post-emergent herbicides used in the maize crop. Among the commercial technologies available, there are some hybrids considered tolerant to this molecule and can present a differential sensitivity, process which is related to the environment, growth stage and herbicide dose. The objective of the study was to determine the sensitivity of corn hybrids to the herbicide nicosulfuron by means of biochemical markers. The first experiment was carried out under greenhouse conditions in a completely randomized design with four replications in a factorial scheme 4 x 2 (hybrids x doses). The herbicide was applied at 0 and 120 g a.i. ha-1, when the plants were in the V3 stage. Electron transport rate (ETR), phytointoxication and plant height were evaluated at 1, 3, 7 and 14 days after treatment (DAT). Plants were collected at 14 DAT to determine its dry weight. The most sensitive and tolerant hybrids were selected to determinate the content of 2-aminobutyric acid and valine, leucine and isoleucine amino acids, in the same evaluation period. The second experiment was arranged in a completely randomized design with five replications in a factorial scheme 8 x 2 (hybrids x doses), the nicosulfuron was applied at 0 and 120 g a.i. ha-1. The experiment was conducted in different periods, for V2 and V6 maize growing stage. One day after the herbicide application, the plants were collected to determine the content of nicosulfuron, 2-aminobutyric and quinic acid, as well as valine, leucine and isoleucine amino acids. During the experiment, the ETR was evaluated at 1, 7, 10, 14, 21 and 28 DAT, and the variables plant height and phytointoxication at 7, 14, 21 and 28 DAT. At 7 DAT the chlorophyll content was determined. Plants were collected at 28 DAT to determine the shoot dry weight. In the first experiment, the collection of the plants one day after application was considered the best period for determination of aminobutyric acid contents, since the greatest accumulation of this compound occurred during that period. The most sensitive hybrid presented higher phytotoxicity values, lower plant height, ETR, dry weight and the highest 2-aminobutyric acid accumulation when compared to the most tolerant hybrid. In the second experiment the eight hybrids presented different sensitivity levels to nicosulfuron. The greatest internal and external herbicide content was observed in V2 stage. The accumulation of 2-aminobutyric acid in the plants after herbicide application occurred for all hybrids in both growing stages, however it was only possible to establish correlations between the accumulation of 2-aminobutyric acid and the sensitivity of the hybrids when the herbicide was applied in the V2 stage.
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Palavras-chave
Ácido aminobutírico, Aminoácidos, Herbicidas inibidores da ALS, Sulfonilureia