Silicon-mediated resistance in maize against infection by Colletotrichum graminicola.

Background and aims: Anthracnose, caused by Colletotrichum graminicola, can greatly reduce yield in maize and alternatives for its management are needed. The hypothesis that maize plants with higher foliar silicon (Si) concentration will increase their resistance against anthracnose was investigated. Methods: Plants were grown in substrate non-supplied or supplied with Si (-Si and + Si plants, respectively) and used to evaluate: (i) the photosynthetic apparatus (leaf gas exchange and chlorophyll (Chl) a fluorescence parameters and photosynthetic pigments concentration), (ii) the activities of defense and antioxidant enzymes and (iii) concentrations of malondialdehyde (MDA) and hydrogen peroxide (H2O2). Results: The + Si plants showed reduced anthracnose symptoms, lower severity and less production of MDA and H2O2 due to higher foliar Si concentration compared to -Si plants. The + Si infected plants showed less impairment in photosynthesis (increased values for rate of net CO2 assimilation, stomatal conductance to water vapor, transpiration rate, variable-to-maximum chlorophyll a fluorescence ratio, photochemical yield and yield for dissipation by down-regulation) and showed higher concentrations of chlorophyll a + b and carotenoids compared to -Si infected plants. Activities of defense (chitinase, β-1,3-glucanase, phenylalanine ammonia-lyase, polyphenoloxidase and lipoxygenase) and antioxidative (ascorbate peroxidase, catalase, superoxide dismutase and peroxidase) enzymes were higher for infected + Si plants compared to infected -Si plants. Conclusion: Maize supplied with Si had their resistance boosted due to a more operative defense response, a robust antioxidative metabolism and a better photosynthetic performance. Using Si to reduce anthracnose epidemic rate and yield losses should be encouraged to promote a more sustainable agriculture. [ABSTRACT FROM AUTHOR]