Evaluation of the Mechanism Responsible for the Low-Level Resistance to Glyphosate in Goosegrass

Abstract

-Goosegrass (Eleusine indica) infests various crops, being reported as low-level resistant (LLR) to glyphosate. The objectives of this study were to evaluate the mechanisms of resistance to glyphosate in goosegrass by the cyt-P450 complex to identify changes in leaf anatomy of these plants and quantify the accumulation of shikimate in biotypes susceptible and with LLR. The metabolic rate was assessed by applying the cyt-P450 malathion inhibitor 30 minutes before the herbicide application. The analysis of the leaf anatomy consisted of a characterization of anatomic cross-sections and evaluation of the effect of glyphosate on the leaf epidermis and the conducting vessels. Plant tissue was collected 24 hours after treatment (HAT) of the dose-response curve to evaluate the accumulation of shikimate. The LLR biotype has not shown glyphosate metabolism by the early application of malathion due to the control of about 65% with or without applying the inhibitor. There is no anatomical evidence to determine the differential absorption of glyphosate by LLR biotypes. However, there is evidence of lower absorption and translocation of glyphosate in this biotype by lower stomatal density and a smaller diameter of the phloem. However, the LLR biotype presents diameter of phloem of 0.027 mm and stomatal density of 91.23 mm -2 , values which are below the observed ones on the susceptible biotype. The susceptible biotype presents shikimate accumulation 17% higher compared to the biotype with LLR at a dose of 1,080 g e.a. ha -1 , allowing to infer that the resistance mechanism is related to the enzyme insensitivity to the herbicide, which enables the use of appropriate management practices to control this weed.Keywords: cyt-P450 monooxygenase, shikimate, absorption and translocation, EPSPs, Eleusine indica. RESUMO -O capim-pé-de-galinha (Eleusine indica) é infestante de diversos cultivos, sendo relatado como resistente de nível baixo (RNB) ao herbicida glyphosate. Os objetivos deste trabalho foram avaliar mecanismos de resistência de capim-pé-de

Morphoanatomic characterization of Gomphrena perennis and Gomphrena pulchella leaves

“…2003) in weed species like Galinsoga parviflora, Conyza bonaeriensis and Ipomoea cairica, considered a potential barrier to penetration of herbicides applied to the canopy, the low stomatal densities in the adaxial side, that were of (48, 42 and 47 stomata mm -2 ) in the adaxial side and of (156, 162 and 143 stomata mm -2 ) in the abaxial side. Ulguin et al (2017), in studies on Eleusine indica, found that characteristics of surface and leaf anatomy may affect the effectiveness of glyphosate absorption by weeds. Features such as composition of the cuticle, number of stomata, and trichomes interfere with the foliar absorption of herbicides and may indicate auxiliary resistance Thus, weeds anatomy characteristics may influence resistance to herbicides, and therefore their determination is important.…”

Monitoring weed mechanical and chemical damage stress based on chlorophyll fluorescence imaging

“…Comparative analysis of the effects of complex stress and single stress on CF parameters of two weeds Compared with single stress, compound stress not only disrupted the physiological pattern of weeds but also directly damaged the leaf structure of weeds, broke the obstruction of weed cuticle layer, made glufosinate enter into weeds faster, and combined with ATP and occupied the reaction site of GS, the synthesis of GS was blocked, and photosynthesis was affected, which made the weeds die much more efficiently (Ulguim et al, 2019;Takano et al, 2020a;Takano et al, 2020b). It is evident from the time that the composite stress leads to the death of the weed in a far shorter time than when a single stress acts on the weed.…”

Morphoanatomic characterization of Gomphrena perennis and Gomphrena pulchella leaves

“…2003) in weed species like Galinsoga parviflora, Conyza bonaeriensis and Ipomoea cairica, considered a potential barrier to penetration of herbicides applied to the canopy, the low stomatal densities in the adaxial side, that were of (48, 42 and 47 stomata mm -2 ) in the adaxial side and of (156, 162 and 143 stomata mm -2 ) in the abaxial side. Ulguin et al (2017), in studies on Eleusine indica, found that characteristics of surface and leaf anatomy may affect the effectiveness of glyphosate absorption by weeds. Features such as composition of the cuticle, number of stomata, and trichomes interfere with the foliar absorption of herbicides and may indicate auxiliary resistance mechanisms.…”