Considering the potential of anthracnose to decrease soybean yield and the need to gain more information regarding its effect on soybean physiology, the present study performed an in-depth analysis of the photosynthetic performance of soybean leaflets challenged with Colletotrichum truncatum by combining chlorophyll a fluorescence images with gas-exchange measurements and photosynthetic pigment pools. There were no significant differences between non-inoculated and inoculated plants in leaf water potential, apparent hydraulic conductance, net CO assimilation rate, stomatal conductance to water vapor and transpiration rate. For internal CO concentration, significant difference between non-inoculated and inoculated plants occurred only at 36 h after inoculation. Reductions in the values of the chlorophyll a fluorescence parameters [initial fluorescence (F), maximal fluorescence (F), maximal photosystem II quantum yield (F/F), quantum yield of regulated energy dissipation (Y(NPQ))] and increases in effective PS II quantum yield (Y(II)), quantum yield of non-regulated energy dissipation Y(NO) and photochemical quenching coefficient (q) were noticed on the necrotic vein tissue in contrast to the surrounding leaf tissue. It appears that the impact of the infection by C. truncatum on the photosynthetic performance of the leaflets was minimal considering the preference of the fungus to colonize the veins.

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.

Considering the potential of white mold, caused by the fungus Sclerotinia sclerotiorum, to reduce tomato production, this study aimed to determinate the effect of manganese (Mn) phosphite on the resistance of tomato plants to this disease by assessing the photosynthetic performance (gas exchange and chlorophyll a fluorescence), the activities of defence enzymes and those related to the antioxidant metabolism as well as the concentrations of photosynthetic pigments, malondialdehyde (MDA), hydrogen peroxide (H2O2) and superoxide anion (O2−). The in vitro assays showed that S. sclerotiorum mycelial growth was inhibited by Mn phosphite in a dose‐response manner. The spray of Mn phosphite reduced white mold severity on the leaves of tomato plants. Additionally, there was a higher foliar Mn concentration for plants sprayed with Mn phosphite. The negative effects of S. sclerotiorum infection in the photosynthetic process were mitigated by Mn phosphite application as noticed by the net carbon assimilation rate, stomatal conductance to water vapour, transpiration rate, maximal photosystem II quantum yield values and concentration of photosynthetic pigments. The concentrations of MDA, H2O2 and O2‐ on inoculated leaves were lower upon Mn phosphite spray. In general, the activities of defence enzymes and those related to the antioxidant metabolism were higher for water‐sprayed plants inoculated with S. sclerotiorum in comparison to those inoculated and sprayed with Mn phosphite. Based on the present study results, the application of Mn phosphite may represent a feasible alternative for white mold management in tomato plants.

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

Considering the importance of blast caused by Pyricularia oryzae in the decrease of rice yield worldwide, this study aimed to assess the photosynthetic performance [leaf gas exchange and chlorophyll (Chl) a fluorescence parameters as well as the photosynthetic pigments concentration], the activities of antioxidant enzymes [ascorbate peroxidase, catalase (CAT), peroxidase (POX), superoxide dismutase (SOD), glutathione peroxidase (GPX), glutathione reductase (GR) and glutathione‐S‐transferase] and concentrations of hydrogen peroxide (H2O2) and malondialdehyde (MDA) in the leaves of rice plants non‐supplied (−Glu) or supplied (+Glu) with glutamate (Glu) and non‐infected or infected by P. oryzae. Blast severity was reduced in the leaves of +Glu plants. On the infected leaves of +Glu plants, the values for internal CO2 concentration were lower while the values for net carbon assimilation rate, stomatal conductance as well as for the concentrations of Chl a, Chl b and carotenoids were higher in comparison to infected leaves of −Glu plants. The functionality of the photosynthetic apparatus was preserved in the infected leaves of +Glu plants. The activities of CAT, GPX, GR, POX and SOD increased in the infected leaves of both −Glu and +Glu plants compared to their non‐inoculated counterparts, but their activities were lower for +Glu plants. The lower activity of these antioxidative enzymes was triggered by the reduced hydrogen peroxide concentration in the infected leaves of +Glu plants resulting in lower MDA concentration. It can be concluded that photosynthesis was less impaired in infected plants supplied with glutamate due to the lower biochemical constraints for CO2 fixation. Moreover, there was a need for lower activity of reactive oxygen species scavenging enzymes in infected leaves of plants supplied with glutamate due to the lower oxidative stress imposed by P. oryzae infection.