Franciele Mariani

Differential susceptibility of biotypes of conyza sumatrensis to Chlorimuron-ethyl herbicide

6 ABSTRACT - Horseweed (Conyza spp.) is an annual weed, infesting soybean crops in southern Brazil, with chlorimuron-ethyl being one of the most commonly used herbicides for its control. However, in recent soybean harvests, an unsatisfactory control of this weed using this herbicide was observed, generating suspicion regarding the selection of resistant biotypes. The objective of this study was to evaluate the susceptibility of horseweed biotypes to the herbicide chlorimuron-ethyl. Two experiments were conducted in a greenhouse; in the first one, the biotypes were selected selected, and the second experiment was arranged in a 5 x 5 factorial in a completely randomized design with four replications. The treatments used in the preparation of the dose response curves were doses of the herbicide chlorimuron-ethyl (0.0, 1.56, 3.13, 6.25, 12.5, and 25 g ha -1 ), applied on the five horseweed biotypes at the 3-4 leaf growth stage. The variables evaluated were visual control percentage and shoot dry weight, compared to the control without herbicide application, and plant acetolactate accumulation. It was concluded that there is a differential susceptibility among the biotypes at doses of less than 20 g ha -1 (dose response curves), which indicates low-level resistance. The practical consequences are the indications of chlorimuron-ethyl application at the maximum doses recomended and that the practice of rotating mechanisms of action must be used in the chemical weed management of these areas.

Weed Management in Soybean — Issues and Practices

Weed management is essential for any current system of agricultural production, especially for large monoculture areas, which exert high pressure on the environment. Soybean is among the largest monoculture registered worldwide, with 102 million hectares harvested only in 2010. The leading countries of production are Argentina, Brazil and the United States, with more than 70% of the total cultivated area. Along with China and India, these five countries represent 90% of all produced soybean. The production incentive is related to growing global demand for oil and protein for food and feed, as well as the feasibility of crops for biodiesel production, extremely important for the global economy.

Properties of the enzyme acetolactate synthase in herbicide resistant canola

Bragantia, Campinas, v. 77, n. 3, p.485-492, 2018 ABSTRACT: Mutations in the gene that encodes the enzyme acetolactate synthase (ALS), conferring plant resistance to ALS inhibitor herbicides, can reduce or inhibit enzymatic function. The objective of this work was to determine the functionality and kinetic characteristics of the enzyme ALS and evaluate the action of the herbicides imazapic (imidazolinone) and metsulfuron-methyl (sulfonylurea) on the activity of the enzyme ALS in canola hybrid Hyola 571CL (imidazolinone resistant), compared to hybrids Hyola 555TT (triazine resistant) and Hyola 61 (conventional). The plants were grown in a greenhouse, and leaves were collected to perform ALS activity analysis. The concentration of pyruvate to provide initial velocity equal to half the maximum reaction rate (Km) and the maximum PLANT PROTECTION Article

Valor adaptativo e habilidade competitiva de azevém resistente e suscetível ao iodosulfuron em competição com o trigo

O objetivo deste trabalho foi identificar e comparar valores adaptativos dos biotipos de azevem (Lolium multiflorum) resistente e suscetivel ao herbicida iodosulfuron e avaliar sua habilidade competitiva com o trigo (Triticum aestivum). Para avaliar o valor adaptativo, os biotipos foram semeados em vasos e coletados a cada 10 dias apos a emergencia, ate os 80 dias. Em cada coleta, avaliaram-se estatura, area foliar e massa seca da parte aerea, e, a partir destas avaliacoes, foram calculadas variaveis indiretas para comparar o crescimento entre os biotipos. A habilidade competitiva foi determinada em experimento de serie de substituicao, tendo-se variado a proporcao da cultura e do competidor. As proporcoes testadas foram: 100:0 (estande puro do trigo), 75:25, 50:50, 25:75 e 0:100% (estande puro do biotipo de azevem resistente ou suscetivel); ja as variaveis avaliadas foram area foliar e massa seca. Os resultados dos estudos comparativos de crescimento mostraram similaridade entre os biotipos de azevem resistente e suscetivel ao iodosulfuron, o que nao caracterizou efeito pleiotropico decorrente da resistencia. Quanto a habilidade competitiva, a competicao interespecifica e prejudicial para o biotipo resistente, enquanto, para o biotipo suscetivel, independe o competidor. A cultura do trigo mostra habilidade competitiva superior a dos biotipos de azevem resistente e suscetivel.

Efeito do glyphosate sobre parâmetros fisiológicos de buva - DOI:10.5039/agraria.v9i4a4342

O objetivo do trabalho foi determinar alteracoes no processo fotossintetico e na inibicao da 5-enolpiruvilchiquimato-3-fosfato sintase (EPSPs), por meio do acumulo de acido chiquimico, apos a aplicacao do herbicida glyphosate, em quatro biotipos de C. sumatrensis, coletados no Estado do Rio Grande do Sul. Para isto foram conduzidos experimentos em casa-de-vegetacao e em laboratorio avaliando fitomassa seca da parte aerea, taxa de fotossintese, transpiracao e eficiencia do uso da agua; a quantidade de acido chiquimico foi calculada para cada tratamento. A aplicacao do glyphosate reduziu o crescimento e afetou a taxa de fotossintese a eficiencia do uso da agua dos biotipos de forma diferencial, sendo que o biotipo resistente teve pequena interferencia do glyphosate enquanto os parâmetros fisiologicos do biotipo suscetivel foram profundamente afetados pelo herbicida. Nos biotipos suscetiveis o acumulo de acido chiquimico foi maior que no biotipo resistente evidenciando sensibilidade diferencial da EPSPs dos biotipos resistente e sensiveis ao glyphosate.