Considering the importance of Asian soybean rust (ASR), caused by Phakopsora pachyrhizi, in the decrease in soybean yield, this study investigated the potential of using phosphite combined with l‐α‐free amino acids (referred to as induced resistance [IR] stimulus hereafter) to boost defence responses of soybean plants against P. pachyrhizi infection. Plants were sprayed with water (control), acibenzolar‐S‐methyl (ASM) or IR stimulus and noninoculated or inoculated with P. pachyrhizi. Urediniospore germination was not affected by the IR stimulus in vitro. Reduced ASR severity, lower malondialdehyde concentration and less colonization of leaf tissues by P. pachyrhizi (lower TEF‐1α expression from 1 to 15 days after inoculation [dai]) occurred for IR stimulus‐sprayed plants. The pattern of gene expression for IR stimulus‐sprayed and infected plants was strikingly similar but sometimes more remarkable than that in ASM‐sprayed and infected plants. Higher production of phenolics and lignin along with stronger up‐regulation of PAL1.3 (5 and 10 dai), PAL2.2 (3 dai), PAL3.1 (1, 3 and 5 dai), ICS1 (5 dai), CHIA1 (1, 5 and 10 dai), CHI1B1 (5 dai), PR‐1A (5 and 10 dai), NR1‐2 (5 and 10 dai) and INR‐2 (5 and 10 dai) for IR stimulus‐sprayed plants increased their resistance against ASR. In addition, IR stimulus‐sprayed and infected plants showed less impairment of the photosynthetic apparatus and maintained high concentrations of chlorophyll a + b and carotenoids. These findings highlight the potential of using this IR stimulus for developing a well‐tuned and effective defensive strategy in soybean plants against P. pachyrhizi infection.
Many diseases greatly impact maize production worldwide, and northern corn leaf blight (NCLB), caused by the fungus Exserohilum turcicum (syn. Setosphaeria turcica) (Leonard & Suggs, 1974) stands out as one of the most important (Munkvold & White, 2016). The symptoms of NCLB are long elliptical, greyish-green or tan lesions, mainly in older leaves of maize plants (Kotze et al., 2019). The necrotic and larger NCLB lesions negatively affect leaf gas exchange (net assimilation rate, stomatal conductance to water vapour, transpiration rate, and internal CO 2 concentration) and chlorophyll (Chl) a fluorescence (maximum quantum yield of photosystem [PS] II, and effective quantum yield of PS II) parameters (Silveira et al., 2019).Moreover, higher electrolyte leakage and greater concentrations of hydrogen peroxide and malondialdehyde occur at the necrotrophic phase of E. turcicum infection in maize leaves (Silveira et al., 2019).Cultural practices such as crop rotation, use of resistant genotypes, and application of foliar fungicides have been used by growers to reduce the impact of NCLB on maize yield (Nelson et al., 2018).Sustainable methods that can be integrated with cultural strategies are needed to ensure cost-effective NCLB control and less environmental impact. Mineral nutrition stands out as an effective strategy
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