Does competition between soybeans and Wild Poinsettia with low-level resistance or susceptibility to glyphosate affect physiology and secondary metabolism?

Abstract

The Wild Poinsettia (Euphorbia heterophylla L.) has elevated potential to reduce the soybean yield and is a difficult to control plant due to herbicide resistance. The objectives of this study were to determine the changes in the photosynthetic physiological parameters, secondary metabolite levels, cellular damage, and antioxidant system activity in soybean plants and Wild Poinsettia biotypes with a low level of resistance or susceptibility to glyphosate in competition with soybeans. Two replacement series experiments were conducted in a greenhouse under competition between soybeans and the low-level resistant biotype (experiment I) or susceptible biotype (experiment II). The treatments consisted of different proportions of soybean plants and Wild Poinsettia [100:0 (pure stand of soybean), 50:50, and 0:100 (pure stand of Wild Poinsettia)] and different evaluation periods (the 2013/14 and 2014/15 growing seasons). The following parameters were analyzed: the chlorophyll, carotenoid (CRT), total phenol, hydrogen peroxide (H 2 O 2 ), and lipid peroxidation levels and the catalase (CAT), ascorbate peroxidase (APX), and superoxide dismutase (SOD) enzyme activity. Generally, competition between the soybeans and the Wild Poinsettia biotypes did not alter the photosynthetic parameters or the photosynthetic pigment levels of the crop. For the weed biotypes, competition with the soybeans negatively affected photosynthesis. Greater losses of chlorophylls and CRTs were observed for the susceptible biotype when in competition with soybeans, whereas the opposite trend was observed for the biotype with a low level of resistance. No cellular damage or alterations in antioxidant system enzyme activity was observed, which indicated a lack of oxidative stress. Key words: Photosynthesis. Stomatal conductance. Chlorophyll. Carotenoids. Euphorbia heterophylla L. ResumoA leiteira (Euphorbia heterophylla L.) apresenta elevado potencial de redução da produtividade de soja, sendo uma planta de difícil controle devido aos casos de resistência a herbicidas. Os objetivos desse trabalho foram determinar a alteração nos parâmetros fisiológicos fotossintéticos, o conteúdo de metabólitos secundários, os danos celulares e a atividade do sistema antioxidante em soja e em biótipo de leiteira resistente de nível baixo ou suscetível ao glyphosate, quando em competição com a soja. Foram realizados dois experimentos em casa de vegetação, em série de substituição, com a competição de soja com o biótipo resistente de nível baixo (experimento I) ou suscetível (experimento II). Os tratamentos constaram das proporções de plantas de soja e leiteira 100:0 (estande puro de soja), 50:50, e 0:100% (estande puro de leiteira); e, das diferentes épocas de condução dos experimentos (safras 2013/14 e 2014/15). Foram analisados o teor de clorofila e carotenoides, fenóis totais, peróxido de hidrogênio, peroxidação lipídica e atividade das enzimas catalase, ascorbato peroxidase e superóxido dismutase. A competição de soja com os biótipos de leiteira, em geral, n...

Defenses Against ROS in Crops and Weeds: The Effects of Interference and Herbicides

“…In soybean and bean, Piasecki et al [ 13 , 14 ] showed that H 2 O 2 levels, APX, and CAT activity decreased with the increase in volunteer corn density, while SOD activity increased commensurate with weed density. Another study documented that the interference of wild poinsettia ( Euphorbia heterophylla ) on soybean did not result in any cellular damage or change in SOD, CAT, and APX enzyme activity in soybean [ 34 ]. Darmanti et al [ 10 ] studied soybean under purple nutsedge ( Cyperus rotundus L.) competition and found reduced activities of SOD, CAT, and APX in soybean.…”

Competitive ability of soybean cultivars with Ipomoea indivisa

“…With the exception of the cultivar DM 66i68 which showed a reduction in LA with an increase in competitor density, possibly due to a genetic differentiation that exists between the cultivars. ULGUIM et al (2017) reported that one of the determining factors for greater competitive capacity is the increase in light interception for chemical energy production by the photosynthetic process. Thus, RP and TRP related to LA prove to be important characteristics in soybean cultivars with greater competitive capacity, when associated with I. indivisa.…”