Soybean Resistance to Cercospora sojina Infection Is Reduced by Silicon

Abstract

Frogeye leaf spot, caused by Cercospora sojina, is one of the most important leaf diseases of soybean worldwide. Silicon (Si) is known to increase the resistance of several plant species to pathogens. The cultivars Bossier and Conquista, which are susceptible and resistant, respectively, to frogeye leaf spot, supplied and nonsupplied with Si were examined for the activities of defense enzymes and the concentrations of total soluble phenolics (TSP) and lignin-thioglycolic acid (LTGA) derivatives at 8, 14, and 16 days after inoculation (dai) with C. sojina. The importance of cell wall degrading enzymes (CWDE) to the infection process of C. sojina and the effect of Si on their activities were also determined. Soybean plants were grown in hydroponic culture containing either 0 or 2 mM Si (-Si and +Si, respectively) and noninoculated or C. sojina inoculated. Severity of frogeye leaf spot was higher in cultivar Bossier plants than cultivar Conquista and also in the +Si plants compared with their -Si counterparts. Except for the concentrations of TSP and LTGA derivatives, activities of defense enzymes and the CWDE did not change for +Si noninoculated plants regardless of the cultivar. The activities of lipoxygenases, phenylalanine ammonia-lyases, chitinases, and polyphenoloxidases as well as the activities of CWDE decreased for the +Si inoculated plants. The results from this study demonstrated that defense enzyme activities decreased in soybean plants supplied with Si, which compromised resistance to C. sojina infection.

Alterations in antioxidant metabolism in coffee leaves infected by Cercospora coffeicola

“…The coffee plant recognized the strains in a similar way and was inhibited by H 2 O 2 produced by the plant, which can be demonstrated through increased POX and APX activity in the first hours of infection. Similar results were reported by NASCIMENTO et al (2014), who verified increased POX and PAL enzyme activity in inoculated soybean plants with Cercospora sojina. POX is a pathogenesis related protein and is induced in the host by the presence of pathogens ( VAN LOON et al, 2006).…”

“…In literature, there are a few accounts of alterations in the antioxidant metabolism of infected plants by Cercospora, mainly when it refers to strains that cause different symptoms in coffee plants (NASCIMENTO et al, 2014). When comparing the two C. coffeicola strains (common BE and black BE), the results showed that both strains were able to induce the activity of enzymes in coffee leaves; however, there was variation in the timing of enzymes activation for each strain depending on the enzyme being analyzed.…”

“…Previously conducted research reported changes in the defense system antioxidant of the plants in response to induced stress by biotic and abiotic agents (DEBONA et al, 2012;NASCIMENTO et al, 2014;DOMICIANO et al, 2015). It is unknown whether the coffee plant responds in a different way to C. coffeicola strains causing the two distinct BE symptoms (common BE and black BE).…”

Changes in leaf gas exchange and chlorophyll a fluorescence on soybean plants supplied with silicon and infected by Cercospora sojina

“…By contrast, Nascimento et al. (, ) noticed an increase in the susceptibility of soybean plants to FLS when supplied with Si. Deshmukh et al.…”

“…Potassium silicate was passed through a cation‐exchange resin (Amberlite IR‐120B, H + form; Sigma‐Aldrich, São Paulo, Brazil) to obtain the monosilicic acid (Ma, Tamai, Ichii, & Wu, ). The Si concentration of 2 mM (+Si) was used to prepare the nutrient solution (Debona et al., ; Nascimento et al., , ) to allow the highest Si uptake by plants during their growth.…”