Physiological and biochemical changes in cucumber infected by Pythium aphanidermatum and the effect of calcium silicate on damage reduction

Pythium aphanidermatum is a cosmopolitan and soil-borne Oomycete which is a root rot pathogen for various species of Cucurbitaceae. The impacts of the pathogen on physiological changes in cucumber plants and the effect of different concentrations of calcium silicate on disease damage reduction were investigated. Three concentrations of calcium silicate, 50, 100 and 150 mg L-1, were applied in this study. Different plant physiological and biochemical mechanisms such as photosynthesis, protein synthesis and antioxidant response were studied. Seedlings were planted in greenhouse and collected after 36 (growing stage) and 71 (flowering stage) days. Chlorophyll, carotenoid, proline, carbohydrates, proteins, anthocyanin contents, lipid proxidation, and catalase activity in the plants were measured. This study showed a decrease in chlorophyll and cartenoid levels and an increase in the levels of the other factors after inoculation. All the measured factors such as proline, carbohydrates, proteins and anthocyanin were increased in healthy plants after adding 100 and 150 mg L-1 calcium silicate compared to the controls. In infected plants which were treated with 100 and 150 mg L-1 calcium silicate, an increase in chlorophyll and carotenoid levels and a decrease in all other monitored factors were observed. The level of chlorophyll, carotenoid, carbohydrate, and prolin in the reproduction stage were significanlty more than the vegetative stage. Based on these findings, application of 150 mg L-1 calcium silicate would reduce the physiological disorders such as plant growth reduction and root rot due to P. aphanidermatum infection of cucumber plants and also better physiology in healthy plantss.