Action of Imazethapyr and Lactofen on the Nodulation of Conventional and Transgenic Soybean under Drought Stress Conditions

Abstract

This research aimed at studying the action of the herbicides imazethapyr and lactofen on the root system and rhizobium/plant interaction, when they are sprayed at two phenological development stages of soybean cultivars under different soil water management. The soybean cultivars MG/BR 46 Conquista (conventional) and BRS Valiosa (RR) were submitted to three minimum soil water potential (Ψs): -0.03; -0.07 and -0.5 MPa at the V2 and V4 phenological stages. The herbicides imazethapyr at the rate (100 g a.i. ha-1) and lactofen at the rate (180 g a.i. ha-1) were sprayed 10 days after the start of water restrictions. Twenty-one days after the application of the herbicides, root dry matter and root nodulation were evaluated. The BRS Valiosa (RR) soybean cultivar presented better nodule formation and a more efficient and more adapted root system to support moderate drought stress conditions (-0.07 MPa). The MG/BR 46 Conquista (conventional) soybean cultivar presented lower the root system growth when submitted to the spraying of imazethapyr and lactofen. The activity of N2-fixating bacteria was affected by the spraying of the herbicides imazethapyr and lactofen.

Seletividade de herbicidas pós-emergentes isolados ou associados a fertilizante foliar na cultura da soja

“…Therefore, these adverse climatic conditions resulted in stress in the development of soybean plants, as the need for water conservation leads to a decrease in photosynthesis and internal translocation (SUZUKI et al 2014), which results in lower photosynthetic rate, lower stomatal conductance, and, finally, lower absorption and translocation of herbicides (ABBOTT & STERLING 2013). In addition, the stress condition of the soybean plants observed in this experiment may have caused changes in the secondary metabolism and in the hormonal levels of the plants, and through the application of herbicides we could observe that the sites of action of these products are also the formation pathways of compounds important for the development and survival of the species (ROCKENBACH et al 2018). GONÇALVES et al (2018 have verified that imazethapyr spraying resulted in decreased root dry matter in the V4 stage.…”

Flumioxazin, imazethapyr and their mixture in the rhizosphere of soybean: effect on early nodulation and biological N fixation

“…The nodulation was also significantly affected by the herbicides, and some studies reported that the symbiosis legume-rhizobia can be affected by herbicides through of some mechanisms: a) reduction of the availability of root hairs to infection (Kremer and Means, 2009); b) inhibition of biochemical signaling by plants to initiate nodulation (Ahemad and Khan, 2011); and c) reduction of cell division, also inhibiting nodule development (Datta et al, 2009). Particularly, some previous studies found that imazethapyr, even when applied at recommended rates, decreased the nodulation in soybean (Parsa et al, 2013;Gonçalves et al, 2018). The results disagree with Gonzalez et al, (1999) who applied flumioxazin, at recommended rate, and did not observe negative effect on nodulation in inoculated soybean.…”

“…For instance, Bohm et al (2009) observed imazethapyr reducing soybean growth but with no significant effect on nodulation and N fixation. However, Gonçalves et al (2018) reported imazethapyr decreasing the root system and nodulation in soybean. In the case of flumioxazin, Gonzalez et al (1999) reported a decreased nodulation with its application on soybean field.…”

“…Indeed, some studies have reported negative effect of flumioxazin and imazethapyr on bacterial community (Pertile et al, 2021), nodulation and biological N fixation (BNF) in the rhizosphere (Bohm et al, 2009;Gonçalves et al, 2018). For instance, Bohm et al (2009) observed imazethapyr reducing soybean growth but with no significant effect on nodulation and N fixation.…”

Biochemical and cytogenetic effects of Imazethapyr on Cicer arietinum L.

“…Many legumes have been reported by a number of authors to extend the effects of IM, such as kharif black gram [5], green gram [6], lentil [7], soybean [8,9], and oilseed rap [10]. Chickpea (Cicer arietinum L., Leguminosae) is the second omnipresent grown legume after soybean worldwide [11,12].…”