Caracterização da resistência de Echium plantagineum aos herbicidas inibidores da enzima acetolactato sintase (ALS)

Abstract

The high degree of genetic variability of plant populations, is one of the main features that allow the survival and adaptation of species under any environmental condition of stress caused to the environment. The continued use of a single herbicide or mechanism of action favors the selection of resistant weeds, which becomes serious problem in the areas of agricultural production. The weeds when living with the cultures interfere in their development and cause losses in productivity and quality of the final product grain. The Echium plantagineum L. species commonly known as flower - Purple was introduced in Brazil with an ornamental purpose, and it is considered a suitable species to produce honey. Currently its significance is related to weed plant, which occurs mainly in the south where inhabits grasslands and winter crops. Currently there are plants that are no longer controlled by the main herbicide used in areas, methyl metsulfurom, acetolactate synthase enzyme inhibitor (ALS). Aiming to confirm the resistance E. plantagineum the group of the ALS herbicides mechanism; assess whether the resistance is linked to the metabolism of the herbicide, as well as understanding the development of the species throughout its cycle and its characteristics morphoanatomic. Three experiments were conducted in greenhouse and laboratory during the years 2016 to 2018 at the University of Passo Fundo (UPF)/Passo Fundo. To evaluate the resistance of the biotypes experiment was conducted in a greenhouse in order to realize the dose response curve four ALS inhibitor herbicides (metsulfurom - methyl, bispyribac-sodium, and piroxulam imazethapyr). For the evaluation of enzymatic properties of ALS and resistance mechanisms unrelated to the site of action, the study-subdivided in two experiments. The first to assess the activity of the ALS enzyme in the presence of imazapic and the concentration of substrate (pyruvate) that provides initial speed equal to half the maximum reaction rate (KM) and maximum reaction velocity (Vmax). The second corresponded to the test metabolism by cytochrome P450 monooxygenase complex. Biotopes as evaluating the growth analysis, morphoanatomical chromosomes and counting were performed three experiments. From the studies it was unable to verify the resistance of the ALS enzyme biotypes, where they were cross-resistant. To assess the enzymatic activity it was found that there was a change of the kinetic parameters of the enzyme to the substrate which in turn also confers biotype resistance R and the high level of susceptibility biotypes S1 and S2. When assessing whether the resistance can be linked to metabolism study showed that there is involvement of the P450 complex in biotype resistance R. Finally parse that biotypes respond differently in the development being that sensitive biotypes have greater development of air already has tough Mays root system development capabilities. As the morphoanatomic features and chromosome counting not found to change.