EFEITO DA APLICAÇÃO DE HERBICIDAS SUPOSTAMENTE ANTAGÔNICOS SOBRE PLANTAS DE ARROZ SUSCETÍVEIS A INIBIDORES DA ENZIMA ACCASE

The control of weedy rice has been widely studied in weed science. However, gene flow from Clearfield rice (CL) to weedy rice has damaged the efficiency of the CL production system. A new rice crop that is resistant to ACCase inhibitor herbicides will be launched in the next year on the market, representing another tool for managing weedy rice in irrigated rice crops. In addition to using this tool, there is a need to increase the spectrum of herbicide treatments to control the diversity of weed species in irrigated rice crops. This study aimed to elucidate the effect of latifolicidal herbicides on the graminicide action of quizalofop on cultivated rice as an indicator plant in the simulation of weedy rice. An experiment was carried out in a greenhouse at the Epagri – Experimental Station of Itajaí, Santa Catarina, Brazil. There was a reduction in the efficiency of rice control for all evaluated doses of quizalofop associated with 2,4-D.O controle do arroz-daninho tem sido foco de pesquisas na área de herbologia. Contudo, a ocorrência de fluxo gênico do arroz Clearfield (CL) para a espécie daninha tem resultado em perda na eficiencia do sistema de produção CL. Uma nova cultivar de arroz, resistente a herbicidas inibidores da ACCase, será lançada no mercado e se constitui em mais uma ferramenta para o manejo do arroz-daninho em lavouras de arroz irrigado. Aliada a essa ferramenta, existe a necessidade de aumento no espectro dos tratamentos herbicidas para o controle da diversidade de espécies de plantas daninhas infestantes nas lavouras de arroz irirgado. O objetivo deste estudo foi elucidar o efeito de herbicidas latifolicidas na ação graminicida do quizalofop sobre o arroz cultivado como planta indicadora na simulação de arroz-daninho. Foi realizado um experimento, em casa de vegetação na Epagri-Estação Experimental de Itajaí (SC). Os resultados obtidos indicam que houve redução da eficiência de controle do arroz em todas as doses avaliadas das associações de quizalofop com 2,4-D

Transgerational effect of sublethal doses of glyphosate and quizalofop and drought stress on Eragrostis plana response to both herbicides

Eragrostis plana is the main invasive plant in the fields of the Pampa Biome. It is a highly invasive and competitive species with the native grassland, that tolerates several abiotic stresses and is difficult control. Plants subjected to abiotic stresses and herbicides can develop mechanisms that alleviate or reduce the damage caused by stressors and transmit this ability to the progenies. The objectives of this work were: 1) to investigate the effect of recurrent application of sub-letal rate of herbicides (quizalofop-p-ethyl or glyphosate) with or without drought stress for two generations may have developed reduction in sensitivity to the herbicide; 2) to investigate whether antioxidant enzymes are involved in this enhanced- reduction in sensitivity process; and 3) to investigate the main enhanced- reduction in sensitivity mechanisms in the development of resistance to glyphosate and quizalofop. F2 generation plants subjected to combined stress (drought stress and glyphosate sub-dose - DRYxGLY) showed the highest tolerance to glyphosate. Antioxidant enzymes in conjunction with the overexpression of EPSPS and the ABC MRP10 transporter are involved in increasing the tolerance of the DRYxGLY population to glyphosate. Generation F2 plants subjected to drought stress (named DRY) developed the highest tolerance to quizalofop. The increase in antioxidant enzyme activity together with the overexpression of the genes CYP72A31, CYP81A12 and GSTL2, are involved in the reduction of oxidative stress and possible metabolization of the herbicide, developing of reduction in sensitivity in the DRY population to quizalofop.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPESEragrostis plana é uma das principais plantas invasoras dos campos do Bioma Pampa. Esta se caracteriza por ser uma espécie altamente invasiva e competitiva com o campo nativo, pela capacidade de tolerar diversos estresses abióticos e pelo difícil controle. Plantas submetidas a estresses abióticos e herbicidas podem desenvolver mecanismos que aliviam ou reduzem os danos causados por estressores e transmitem essa capacidade às progênies. Os objetivos deste trabalho foram: 1) investigar o efeito da aplicação recorrente de dose sub-letal dos herbicidas (quizalofop-p-ethyl ou glyphosate) com ou sem estresse por seca por duas gerações no desenvolvimento de maior tolerância aos herbicidas; 2) investigar se as enzimas antioxidantes estão envolvidas nesse processo de tolerância aprimorada; e 3) investigar os principais mecanismos de tolerância aprimorada no desenvolvimento de resistência ao glyphosate e quizalofop. Plantas da geração F2 submetidas ao estresse combinado (estresse por seca e subdose de glyphosate - DRYxGLY) apresentaram a maior tolerância ao glyphosate. As enzimas antioxidantes conjuntamente com a superexpressão de EPSPS e do transportador ABC MRP10 estão envolvidos no aumento da tolerância da população DRYxGLY ao glyphosate. Plantas da geração F2 submetidas ao estresse por seca (denominada DRY) desenvolveram a maior tolerância ao quizalofop. O aumento da atividade enzimática antioxidante conjuntamente com a superexpressão dos genes CYP72A31, CYP81A12 e GSTL2, estão envolvidos na redução do estresse oxidativo e possível metabolização do herbicida, desenvolvendo a tolerância na população DRY ao quizalofop

High Atmospheric CO₂ Concentration Mitigates Drought Effects on <i>Acanthostyles buniifolius</i> an Important Grassland Weed in South America

The differential growth and yield response of plant species to rising carbon dioxide concentrations and climatic change may alter species diversity within biomes. The Pampa Biome in South America is an important grassland biome of agronomic and environmental importance. Acanthostyles buniifolius (Chirca) is one of the most important weeds in natural pasture areas widely distributed in southern South America and can adversely affect livestock production. The current study was designed to identify possible responses of Chirca to CO2 concentration ([CO2]) and drought that would indicate higher adaptation and potential proliferation within the Pampa Biome. Chirca plants were cultivated at two CO2 concentrations (400 (a[CO2]) and 700 (e[CO2]) µmol mol−1) and two water conditions (under water restriction—15% of the pot capacity; and plants without water restriction—pot capacity). Besides growth parameters, we also determined water potential (ѱw), relative water contents (RWC), proline, glycine betaine, total soluble sugars, hydrogen peroxide, lipid peroxidation, superoxide dismutase (SOD), ascorbate peroxidase (APX) activity, chlorophyll A and B, carotenoids and root dry mass (RDM). Plants exposed to e[CO2] are more efficient in water use and have a greater increase in root dry mass, enabling greater adaptation to climate-induced droughts. Among the biochemical changes observed in the plants under drought stress, the accumulation of proline, glycine betaine, and total soluble sugars were the most evident mechanisms allowing plants to tolerate drought stress by osmotic adjustment