Evolution of Natural Resistance to Glyphosate in Morning Glory Populations

Abstract

-Tolerance, also referred to as natural resistance, is a feature that exists in the plant even before herbicide application in an area. I. grandifolia, I. indivisa and I. purpurea are among the tolerant species most commonly found over fields in southern Brazil. We hypothesized that the intensive use of glyphosate results in increasing levels of tolerance to glyphosate, and in pronounced response variability in populations of the same Ipomoea species. This study aimed at identifying tolerance variations to glyphosate among I. grandifolia, I. indivisa and I. purpurea morning glory species and among populations of these species. In crops over Paraná and Santa Catarina states (Brazil) 31 biotypes were collected (20 I. grandifolia, 7 I. indivisa and 4 I. purpurea), on which were applied 0, 216, 432, 864, 1,296, 1,728 and 2,160 g a.e. ha -1 of glyphosate and the dose required to reduce 50% of dry matter (GR 50 ) was determined. Biotypes of all tested Ipomoea species showed variability of glyphosate tolerance. Tolerance factors had greater amplitude among biotypes of I. gradifolia and I. indivisa species (between 1.7 and 33.6 and between 3.3 and 34.2, respectively) than in I. purpurea (between 3.7 and 4.9). Especially within I. gradifolia e I. indivisa species, some biotypes required a much higher dose than the recommended one to control the wild biotype, indicating progress in the level of glyphosate tolerance; this proves the initial hypothesis of this work. Keywords

Phytotoxic Neocassane Diterpenes fromEragrostis plana

“…The herbicide glyphosate has a broad spectrum of action and a high degree of phytotoxicity on harmful species and considered as one of the molecules with the greatest impact on agriculture currently used . The plants E. heterophylla and I. grandifolia are tolerant to glyphosate , in more advanced stages of development; however, in the seedling stage, as utilized in the present assays, there are fewer barriers until the herbicide reaches the site of action (EPSPs enzyme), and thus its efficiency is higher.…”

Residual de herbicidas aplicados na soja sobre o milho safrinha e controle de Digitaria insularis

“…Com os presentes resultados pode-se observar que a mistura dos herbicidas flumioxazina + imazetapir apresenta melhores resultados de controle quando aplicados de forma juntos do que quando aplicados isoladamente, aumentando assim a capacidade de controle de plantas daninhas, quando comparado com aplicação dos herbicidas isolados para o controle de espécies eudicotiledôneas. Isso demonstra que a interação entre diferentes moléculas é importante para a obtenção do controle efetivo de plantas daninhas, muitas vezes apresentando melhores do que aqueles quando esses princípios ativos são aplicados separadamente (Pazuch et al, 2017;Spadotto et al, 2017), como demonstrado no presente trabalho. As espécies monocotiledôneas encontradas na área foram capim-colchão (Digitaria horizontalis), timbete (Cenchrus echinatus), capim pé de galinha (Eleusine indica) e trapoeraba (Comellina sp.).…”

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“…Later, Monquero and Silva (2007) also reported that this molecule did not efficiently control I. purpurea. Additionally, Pazuch et al (2017) reported new tolerance to this herbicide in Ipomoea spp. in the southern region of Brazil, which makes the future of the management of this invasive species in the country worrying.…”