Red-light treatment induces resistance in bell pepper to Phytophthora capsici

This study was conducted to investigate the effects of red-light treatment on inducing resistance in bell pepper to Phytophthora capsici. Seeds of bell pepper (Capsicum annuum, ‘Hybrid SPP 6112’) were sown in 10-cm-diameter plastic pots containing steamed soil mix and were grown on a greenhouse bench under red light irradiation (600-700 nm) from fluorescent tubes. The fluorescent tubes provided red light with an intensity of 287 µW cm^-2, which was a supplement to natural daylight. Control seedlings were kept under white light (WL) or under natural daylight (NDL) in the same greenhouse. Three- and four-week-old seedlings were inoculated with a zoospore suspension of P. capsici (20×10⁴ zoospores mL^-1 water). Plants were evaluated for damping-off symptoms every day for 15 days after inoculation. Red-light treatment of seedlings reduced Phytophthora damping-off by up to 73%. Red-light treatment for four weeks was significantly more effective than red-light treatment for three-week in reducing Phytophthora damping-off.