The Effects of Soil Phosphorus Levels on Capsaicinoid and Sugar Contents in Chili Pepper (Capsicum spp.)

抄録

The capsaicinoid and sugar contents in chili peppers vary with changing environmental factors. The present multi-year experiment was conducted to determine the effects of soil phosphorous on capsaicinoid levels and sugar content in the fruit of four Capsicum annuum varieties (‘Takanotsume’, ‘ST-2’, ‘Sapporo Oonaga Namban’ and ‘Shishito’) and one C. chinense variety (‘Habanero’). Experiment 1 was conducted under open field conditions and in greenhouses at Shinshu University (Minamiminowa, Nagano) in 2007, in which soil samples from four farmer’s fields were used and the research fields were treated with phosphorus fertilizer for the ‘Takanotsume’ and ‘ST-2’ cultivars. In 2008, 2010, 2011, 2018 and 2020, different levels of this fertilizer were applied and the flavor components, including capsaicinoid, of the fruits were measured. The 2007 results from Experiment 1 showed that phosphorus, remaining in the soil, reduced the capsaicinoid content in ‘Takanotsume’ and ‘ST-2’. However, this increased from 100 to 200 g·m^-2 and then decreased at the 300 g·m^-2 phosphorus fertilizer applied in ‘Takanotsume’ (2008, 2010, 2011 and 2018), ‘Sapporo Oonaga Namban’ and ‘Habanero’ (2018). These results revealed that the capsaicinoid content increased with the increment of phosphorus fertilizer and tended to decrease with excess phosphorus application. There was a tendency for the total sugar and glucose contents to increase slightly when the plants were grown in soil with high amounts of phosphorus (300 g·m^-2 and 600 g·m^-2).