Low level resistance of wild poinsettia biotypes to glyphosate and alternative chemical control

Abstract

In the State of Rio Grande do Sul (RS), Southern Brazil, glyphosate has not been capable of controlling wild poinsettia (Euphorbia heterophylla L.) in soybean fields, thus, suggesting resistance to this herbicide. Therefore, this study aimed at evaluating sensitivity of wild poinsettia biotypes to glyphosate, identifying the occurrence of resistance of wild poinsettia to the herbicide in RS state and determining the resistance factor of wild poinsettia biotypes under suspicion, besides assessing other herbicides as alternative controls. Two greenhouse experiments, which lasted two years, were conducted by a completely randomized design with four replications. Six biotypes (Factor A) and eight doses of glyphosate (Factor B) were used for getting the dose-response curve. Regarding the alternative control, post-emergence herbicides for soybean and corn crops were tested. Control and dry mass of the shoot were analyzed as variables. Resistance factors of resistant biotypes 20.2 and 21.1 were 4.83 and 5.29, respectively, by comparison with the susceptible biotype (11.4). In RS state, there has currently been high selection pressure due to the intensive use of glyphosate against wild poinsettia plants, as the result of the occurrence of biotypes 20.2 and 21.1 which have low levels of resistance to glyphosate and very little control by ALS-inhibiting herbicides. Therefore, an alternative to mitigate the problem is the use of herbicides with different mechanisms of action.

2,5-Diketopiperazines via Intramolecular N-Alkylation of Ugi Adducts: A Contribution to the Synthesis, Density Functional Theory Study, X-ray Characterization, and Potential Herbicide Application

“…49,50 Wild poinsettia has become a serious problem in soybean production in Brazil for its ability to select for herbicide resistance. There are numerous reports regarding the occurrence of resistance to various herbicides in wild poinsettia, including acetolactate synthase (ALS) inhibitors, ALS and protoporphyrinogen oxidase (PPO) inhibitors, 51 glyphosate, 52 and recently to imazamox. 53 Therefore, the results obtained in the present work inspire great interest due to the possibility of applying compounds that have selective phytotoxic activity as possible herbicides or as models for the synthesis of more potent analogues.…”

Evolution of EPSPS double mutation imparting glyphosate resistance in wild poinsettia (Euphorbia heterophylla L.)

“…After this time period, plants were able to regrow from the axils forming new branches and completing their life cycle. The LD 50 and MR 50 values for the GR population (624-721 g ha -1 ) were higher than those observed previously (263-433 g ha -1 ) [33,34]. While different wild poinsettia populations could have evolved GR in the past [33], no resistance mechanism has been investigated so far.…”

Fitness Cost of Imazamox Resistance in Wild Poinsettia (Euphorbia heterophylla L.)

“…Wild poinsettia (Euphorbia heterophylla L.), a weed species native to South America [15], causes losses of crop yields in crops such as cotton, soybean, peanut [16], maize and tomato in Africa, Asia, the Mediterranean region and North America [17]. Furthermore, this weed is reported to reduce the quality of the crop at the harvest [18].…”

“…Wild poinsettia has become a serious problem in soybean production in Brazil for its ability to select for herbicide resistance. There are numerous reports regarding the occurrence of resistance to various herbicides in wild poinsettia, including acetolactate synthase (ALS) inhibitors [19], ALS and protoporphyrinogen oxidase (PPO) inhibitors [20], and glyphosate [18,21]. Additionally, a new case of imazamox resistance in wild poinsettia was reported recently by Rojano-Delgado et al [22].…”