Relationship between Salinity Stress and the Contents of Sugar, Glutamic Acid and Capsaicinoids in the Fruit of Chili pepper (Capsicum spp.)

抄録

The amounts of the taste components sugars, glutamic acid, and capsaicinoids in Chili pepper fruits (Capsicum spp.) change depending on environmental factors. The present study was conducted to evaluate the effects of salinity stress and harvesting days after flowering (DAF) on the sugar, glutamic acid, and capsaicinoid contents of the Chili pepper ‘Manganji’, ‘Fushimiamanaga’, ‘Sapporo Oonaga Namban’ (C. annuum), and ‘Habanero’ (C. chinense). Experiments were conducted in a greenhouse from April to October in 2018 and 2019. Three levels of salinity stress were applied: control (0.9 dS m^-1), additional (5 dS m^-1), and excessive (10 dS m^-1). Fruit was harvested at 20, 30, 40, and 50 DAF. The fruit weight (g) and contents of glucose, total sugar, and glutamic acid were measured using a portable spectrophotometer, and the capsaicinoid content was measured by high-performance liquid chromatography. The Brix and the contents of total sugar, glutamic acid, and capsaicinoids increased, while the glucose content decreased with the delay in harvesting. In the excessive salinity group, the glucose content tended to be lower, but the Brix and the contents of total sugar, glutamic acid, and capsaicinoids tended to be higher than those of the control group at each harvesting DAF in all Chili pepper.