DIFFERENTIAL RESPONSE OF CLONES OF EUCALYPT TO GLYPHOSATE1

Weed control is commonly performed by the inter-row mechanical weeding associated to intrarow glyphosate directed spraying, causing a risk for drift or accidental herbicide application, that can affect the crop of interest. The objective was to evaluate the response of clones C219, GG100, I144, and I224 of eucalypt (Eucalyptus grandis x E. urophylla) to glyphosate doses of 0, 18, 36, 72, 180, 360, and 720 g of acid equivalent per hectare. The clones showed different growth patterns with regard to height, leaf number, stem dry weight, relative growth rate, net assimilation rate, and relative leaf growth rate. The clones I144 and GG100 were more susceptible to glyphosate, showing the doses required to reduce dry weight by 50% of 113.4 and 119.6 g acid equivalent per hectare, respectively. The clones C219 and I224 were less susceptible to glyphosate, showing the doses required to reduce dry weight by 50% of 237.5 and 313.5 g acid equivalent per hectare, respectively. Eucalyptus clones respond differently to glyphosate exposure, so that among I224, C219, GG100, and I144, the susceptibility to the herbicide is increasing.O controle de plantas daninhas é comumente feito com roçadas na entrelinha associada a aplicações dirigidas de glyphosate na linha de plantio de culturas arbóreas, acarretando risco de deriva ou aplicação acidental do herbicida, que pode afetar a cultura de interesse. O objetivo foi avaliar a resposta dos clones C219, GG100, I144 e I224 de eucalipto (Eucalyptus grandis x E. urophylla) a doses de glyphosate de 0, 18, 36, 72, 180, 360 e 720 g de equivalente ácido por hectare. Os clones apresentaram padrões de crescimento distintos no que se refere a altura da planta, número de folhas, massa seca do caule, taxa de crescimento relativo, taxa de assimilação líquida e taxa de crescimento foliar relativo. Os clones I144 e GG100 foram mais suscetíveis ao glyphosate, sendo as doses necessárias para reduzir a massa seca em 50% de 113,4 e 119,6 g ea ha-1, respectivamente. Os clones C219 e I224 foram menos suscetíveis ao glyphosate, sendo as doses necessárias para reduzir a massa seca em 50% de 237,5 e 313,5 gae ha-1, respectivamente. Clones de eucalipto respondem diferentemente à exposição ao glyphosate, e entre I224, C219, GG100 e I144 a suscetibilidade é aumentada.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Univ Estado Santa Catarina, Ctr Ciencias Agrovet, Dept Agron, Lages, SC, BrazilUniv Estadual Paulista, Fac Ciencias Agr &Vet, Dept Biol Aplicada Agropecuaria, Jaboticabal, SC, BrazilUniv Estado Santa Catarina, Programa Posgrad Producao, Lages, SC, BrazilUniversidade Estadual Paulista, Faculdade de Ciências Agrárias e Veterinárias, Departamento de Biologia Aplicada à Agropecuária, Jaboticabal, SC - Brasi

Hormesis with glyphosate depends on coffee growth stage

Os sistemas de manejo de plantas daninhas em quase todos os pomares de café do Brasil permitem que o herbicida pulverizado sofra deriva sobre a cultura. Com objetivo de avaliar se há algum efeito do glyphosate, herbicida mais comumente utilizado em pomares de café, sobre as plantas de café, uma ampla faixa de doses do herbicida foi aplicada diretamente sobre plantas de café em dois distintos estádios de crescimento da planta. Embora o crescimento de ambas as plantas novas e velhas tenha sido reduzido em doses mais altas de glyphosate, baixas doses não causaram efeitos sobre características de crescimento de plantas novas e estimularam o crescimento das mais velhas. Portanto, o efeito hormético do glyphosate é dependente do estádio de crescimento da planta de café no momento da aplicação do herbicida.Weed management systems in almost all Brazilian coffee plantations allow herbicide spray to drift on crop plants. In order to evaluate if there is any effect of the most commonly used herbicide in coffee production, glyphosate, on coffee plants, a range of glyphosate doses were applied directly on coffee plants at two distinct plant growth stages. Although growth of both young and old plants was reduced at higher glyphosate doses, low doses caused no effects on growth characteristics of young plants and stimulated growth of older plants. Therefore, hormesis with glyphosate is dependent on coffee plant growth stage at the time of herbicide application.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Universidade do Estado de Santa Catarina (UDESC) Centro de Cencias Agroveterinarias Departamento de AgronomiaUniversidade Estadual Paulista Faculdade de Cencias Agrarias e Veterinarias Departamento de Biologia Aplicada a AgropecuariaUniversity of Mississippi Natural Products Utilization Research Unit United States Department of AgricultureUniversidade Estadual Paulista Faculdade de Cencias Agrarias e Veterinarias Departamento de Biologia Aplicada a Agropecuari

Pool of Resistance Mechanisms to Glyphosate in Digitaria insularis

Digitaria insularis biotypes resistant to glyphosate have been detected in Brazil. Studies were carried out in controlled conditions to determine the role of absorption, translocation, metabolism, and gene mutation as mechanisms of glyphosate resistance in D. insularis. The susceptible biotype absorbed at least 12% more C-14-glyphosate up to 48 h after treatment (HAT) than resistant biotypes. High differential C-14-glyphosate translocation was observed at 12 HAT, so that >70% of the absorbed herbicide remained in the treated leaf in resistant biotypes, whereas 42% remained in the susceptible biotype at 96 HAT. Glyphosate was degraded to aminomethylphosphonic acid (AMPA), glyoxylate, and sarcosine by >90% in resistant biotypes, whereas a small amount of herbicide (up to 11%) was degraded by the susceptible biotype up to 168 HAT. Two amino acid changes were found at positions 182 and 310 in EPSPS, consisting of a proline to threonine and a tyrosine to cysteine substitution, respectively, in resistant biotypes. Therefore, absorption, translocation, metabolism, and gene mutation play an important role in the D. insularis glyphosate resistance.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)MICINN (Spain)São Paulo State Univ, Dept Appl Biol Agr, BR-14884900 Jaboticabal, BrazilUniv Cordoba, Dept Agr Chem & Edaphol, E-14071 Cordoba, SpainCSIC, Inst Agr Sostenible, E-14080 Cordoba, SpainUniv Cordoba, Dept Analyt Chem, E-14071 Cordoba, SpainSão Paulo State Univ, Dept Appl Biol Agr, BR-14884900 Jaboticabal, BrazilMICINN (Spain): AGL2010-1677

Pro-106-Ser mutation and EPSPS overexpression acting together simultaneously in glyphosate-resistant goosegrass (Eleusine indica)

Glyphosate has been used for more than 15 years for weed management in citrus groves in the Gulf of Mexico, at up to 3–4 applications per year. Goosegrass (Eleusine indica (L.) Gaertn.) control has sometimes failed. In this research, the mechanisms governing three goosegrass biotypes (Ein-Or from an orange grove, and Ein-Pl1 and Ein-Pl2 from Persian lime groves) with suspected resistance to glyphosate were characterized and compared to a susceptible biotype (Ein-S). Dose-response and shikimate accumulation assays confirmed resistance of the resistant (R) biotypes. There were no differences in glyphosate absorption, but the R biotypes retained up to 62–78% of the herbicide in the treated leaf at 96 h after treatment (HAT), in comparison to the Ein-S biotype (36%). The 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) activity in the Ein-Or and Ein-S biotypes was over 100-fold lower than the Ein-Pl1 and Ein-Pl2 ones. The latter showed a high EPSPS-basal activity, a mutation at Pro-106-Ser position in the EPSPS gene, and EPSPS overexpression. The EPSPS basal and EPSPS overexpression were positively correlated. The R goosegrass biotypes displayed poor glyphosate translocation. Furthermore, this grassweed showed, for the first time, two mechanisms at the target-site level (Pro-106-Ser mutation + EPSPS overexpression) acting together simultaneously against glyphosate