Nickel potentiates soybean resistance against infection by Phakopsora pachyrhizi

Abstract

Asian soybean rust (ASR), caused by the fungus Phakopsora pachyrhizi, causes significant yield losses worldwide. Nickel (Ni) plays a key role in the metabolism of some profitable crops, such as soybeans, because it is a constituent of several biomolecules and is required for the catalytic process of several enzymes. This study investigated the effect of foliar Ni treatment on the potentiation of soybean cultivar TMG 135 resistance to P. pachyrhizi infection at the microscopic, biochemical, and molecular levels. The severity of ASR decreased by 35% in plants treated with Ni. The malondialdehyde concentration, an indicator of cellular oxidative damage, was high in the leaves of plants that were not treated with Ni and was linked to ASR severity and the extensive colonization of the palisade and spongy parenchyma cells by fungal hyphae. The lignin concentration, β‐1,3‐glucanase activity, and expression of the URE gene and the defence‐related genes PAL1.1, PAL2.1, CHI1B1, and PR‐1A were up‐regulated in Ni‐treated plants infected with P. pachyrhizi. The information provided by this study shows the great potential of Ni to increase the basal level of soybean resistance to ASR and to complement other control methods within the context of sustainable agriculture.

Glyphosate and nickel differently affect photosynthesis and ethylene in glyphosate‐resistant soybean plants infected by Phakopsora pachyrhizi

“…In this study, we report the effects of Gl and additional foliar Ni application on soybean resistance against P. pachyrhizi infection. Earlier reports demonstrated that Gl and Ni application decreased ASR development on soybean plants (Feng et al 2005, 2008, Einhardt et al 2020). The results of this study corroborate those reports and provide novel evidence of an additional effect of the combination of Ni and Gl on the maintenance of the photosynthetic capacity of infected plants.…”

“…Plants (V4 growth stage and with three fully expanded leaves) were sprayed with a solution (7.2 ml per plant; pH 6.0) of 0.19 g l −1 NiSO 4 .6H 2 O. This dose was used based on the study carried out by Einhardt et al (2020). At 24 h after Ni spray, plants were sprayed with Roundup Original® (Monsanto) (7.2 ml per plant of a solution of 0.667 g l −1 of acid equivalent of N‐(phosphonomethyl) glycine (Gl); equivalent to 960 g ha −1 a.e.).…”

“…Plants sprayed with water (control) served as the control treatment. At 24 h after Gl spray, corresponding to 48 h after Ni spray, plants were inoculated with P. pachyrhizi as described by Einhardt et al (2020). The urediniospores were collected from soybean plants (cultivar ‘TMG132’) previously inoculated with the monouredinial isolate UFV‐DFP Pp 25 of P. pachyrhizi .…”

“…The deficiency of this micronutrient might occur in soybean plants without visual symptoms with a reduction in the foliar iron concentration and effects on the photosynthetic process (Freitas et al 2019). Ni has shown the potential to control powdery mildew (Barcelos et al 2018) and ASR (Einhardt et al 2020) in soybean. In Microsphaera diffusa infected soybean, the reduced powdery mildew severity for Ni‐sprayed plants was related to a more robust antioxidant metabolism (Barcelos et al 2018).…”

“…In Microsphaera diffusa infected soybean, the reduced powdery mildew severity for Ni‐sprayed plants was related to a more robust antioxidant metabolism (Barcelos et al 2018). For the interaction between soybean and P. pachyrhizi , Ni potentiated host defense responses against fungal infection by increasing β ‐1,3‐glucanase activity, expression of genes coding for urease, chalcone isomerase and phenylalanine ammonia‐lyase as well lignification of leaf tissues (Einhardt et al 2020).…”