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.

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Leaf blast, caused by the hemibiotrophic fungus Pyricularia oryzae, is the most important disease affecting rice production worldwide. The present study investigated the potential of using glutamate (Glu) to increase rice resistance to leaf blast. Rice plants (cultivar Metica-1) were non-supplied (−Glu) or supplied (10 mM) (+Glu) with Glu and non-inoculated or inoculated with P. oryzae. Leaf blast severity and the number of lesions per cm 2 of leaf were significantly lower by 55 and 50%, respectively, for +Glu plants in comparison to -Glu plants at 96 h after inoculation (hai). The area under the leaf blast progress curve was significantly lower by 70% for +Glu plants in comparison to -Glu plants. For inoculated +Glu plants, the activities of chitinase, β-1-3-glucanase, phenylalanine ammonia-lyase, and polyphenoloxidases as well as the concentrations of total soluble phenolics and lignin-thioglycolic acid derivatives were significantly higher for inoculated +Glu plants in comparison to inoculated -Glu ones. The use of glutamate may become an alternative to be used in the management of rice blast in the context of a sustainable agriculture.

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The aim of the present study was to investigate the influence of tyrosine on the in vitro growth and the production of the betacyanin pigment in Alternanthera philoxeroides and A. tenella. Nodal segments were inoculated in MS medium containing different concentrations of tyrosine (0, 25, 50 and 75 µM)

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Blast, caused by Pyricularia oryzae, is one of the most important diseases affecting rice yield worldwide. This study investigated the potential of silicon (Si) to counteract the effect of picolinic acid (PA), a non-host selective toxin produced by P. oryzae, on the photosynthetic performance, on the activities of defense enzymes, and the antioxidative metabolism of rice plants. Plants were grown in nutrient solution containing 0 or 2 mM of Si and non-sprayed or sprayed with PA (0.5 mg PA/ml; 20 ml per plant) at 35 days after emergence. The PA-sprayed plants exhibited necrotic lesions on leaves that resembled those caused by P. oryzae infection. In the presence of Si, the necrotic lesions on the leaves of PA-sprayed plants were less in number and of reduced size. The necrosis of leaf tissues caused by PA spray was accompanied by lower values of net CO 2 assimilation rate and transpiration rate and high internal CO 2 concentration values indicating the occurrence of biochemical limitations in photosynthesis regardless of Si supply. For plants non-sprayed with PA, there was no change in the activities of the enzymes involved in host defense (chitinases (CHI), β-1,3-glucanases (GLU), polyphenoloxidases (PPO), and phenylalanine ammonia-lyases (PAL)) and on the antioxidative system (superoxide dismutases (SOD), catalases (CAT), peroxidases (POX), ascorbate peroxidases (APX), and glutathione reductases (GR)). The activities of CHI, GLU, PAL, GR, POX, and SOD were greater on the leaves of PA-sprayed plants in the absence of Si than on its presence. Silicion did not alleviate the physiological and biochemical aspects of PAmediated stress on rice leaf blades. We hypothesize that Si forms a physical barrier. Such physical impediment makes the diffusion of PA into the leaf blades more difficult rather than actively affecting the physiology and biochemistry of the plant.

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