Some biochemical defense responses enhanced by soluble silicon in bitter gourd-powdery mildew pathosystem

Soil application of rice husk as a natural silicon source to enhance some chemical defense responses against foliar fungal pathogens and growth performance of Bitter Gourd (<em>Momordica charantia L.</em>)

“…It was interesting to note that, disease severity of rice husk treated plants was significantly lower (P<0.05) than that of control plants during the entire period of experiment and both GRH and RHA were equally effective in reducing the disease severity. A clear reduction in downy mildew severity and levels of leaf accumulated Si was reported recently for bitter gourd plants grown in potassium silicateamended media (Ratnayake et al, 2016b). The reduction of disease severity and levels of foliar accumulated Si in plants grown on rice husk-amended media were comparable with those grown in potassium silicate-amended media.…”

“…Severity of downy mildew disease (the most common disease during the period of investigation) in leaves was rated separately through external observations on weekly basis using a self-prepared scale (0 = no disease, 1 = 1 to 20%, 2 = 21 to 40%, 3 = 41 to 60%, 4 = 61 to 80%, and 5 = 81 to 100% of upper leaf surface covered with disease) (Ratnayake et al, 2016b). As all the treated and control plants were arranged randomly in the field and fertilization, watering and other field practices were applied similarly to each pot, it was assumed that all the plants got identical level of inoculums.…”

“…Method used to extract PPO was based on our previous experiments (Ratnayake et al, 2016c). This method involved spectrophotometric measurement of the change in intensity of a dark coloured polymeric compound resulted from oxidation of catechol of the reaction mixture upon adding leaf extracts.…”

“…and downy mildew caused by Pseudoperonospora sp. (Ratnayake et al, , 2015(Ratnayake et al, , 2016a(Ratnayake et al, and 2016b. The reduction of disease severity could partly be attributed to Si-enhanced chemical defense responses including elevated activity of enzymes; peroxidase, polyphenol oxidase and pathogenesis-related proteins; chitinase and β-1, 3-glucanase in leaf tissues (Ratnayake et al, 2016c).…”

“…(Ratnayake et al, , 2015(Ratnayake et al, , 2016a(Ratnayake et al, and 2016b. The reduction of disease severity could partly be attributed to Si-enhanced chemical defense responses including elevated activity of enzymes; peroxidase, polyphenol oxidase and pathogenesis-related proteins; chitinase and β-1, 3-glucanase in leaf tissues (Ratnayake et al, 2016c). In this context, the aims of the current work were to ascertain the effectiveness of soil amendment with rice husk as a natural Si source in controlling foliar fungal diseases, and the effects on some growth and yield parameters of bitter gourd plant.…”