Silicon Suppresses Phytophthora Blight Development on Bell Pepper

摘要

The application of silicon (Si) reduces the intensity of diseases in several economically important crops. This study aimed at determining the potential of this element to decrease the symptoms of Phytophthora blight development on bell pepper, caused by Phytophthora capsici. Bell pepper plants (Sakata Hybrid X pp6115) were initially grown in plastic pots with substrate composed of 1 : 1 mixture of sterile fine sand and Fafard No. 2 peat mix amended with calcium silicate (+Si) or calcium carbonate (-Si). Six weeks later, plants were transplanted to new pots that contained the same +Si and -Si substrate but were infested with finely ground wheat grains (1- to 2-mm diameter) colonized by two isolates of P. capsici, Cp30 (compatibility type A1) and Cp32 (compatibility type A2). At the end of the experiment, roots and stems from plants of each treatment were collected to determine Si concentration. The presence of lesions on crowns and stems and wilting of plants were monitored up to 9 days after transplanting (DAT). Data obtained were used to calculate the area under diseased plants progress curve (AUDPPC) and area under wilting plants progress curve (AUWPPC). Relative lesion extension (RLE) was obtained as the ratio of vertical lesion extension to stem length at 9 DAT. There was a 40% increase in the concentration of Si in the roots but not in the stems of bell pepper plants in the +Si treatment compared to the -Si treatment. When comparing +Si to -Si treatments, the AUDPPC was reduced by 15.4 and 37.5%, while AUWPPC was reduced by 29.1 and 33.3% in experiments 1 and 2, respectively. RLE values were reduced by 35% in the +Si treatment. Dry root weights increased by 23.7%, and stem weights were increased by 10.2% in the +Si treatment. Supplying Si to bell peppers roots can potentially reduce the severity of Phytophthora blight while enhancing plant development.