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).

The present study was conducted to determine the effects of excess phosphorus fertilizer application on number of seeds, placental septum weight, and capsaicinoid content in ‘Takanotsume’, ‘Sapporo Oonaga Namban’ and ‘Shishito’ (only used in 2020) chili pepper varieties under different phosphorus fertilizer treatments in 2020 (60, 300 and 600 g·m^-2) and in 2021 (100 and 600 g·m^-2). Furthermore, this research is also to determine the relative expression levels of capsaicinoid biosynthesis genes in 2021. With the increasing amount of P fertilizer added, the number of seeds and placenta dry weights did not change, but the capsaicinoid content was significantly lower in all varieties except for the ‘Shishito’. Relative expression levels of 18 capsaicinoid biosynthesis genes were tested using a quantitative reverse transcription-polymerase chain reaction (qRT-PCR) in 2021. The genes were divided into four groups based on their expression patterns. Group 1 showed a higher gene expression of Pun1, pAMT, ACL and CaKR1 genes in plants grown in 100 g·m^-2 P-treated soil for both cultivars at 20 days after flowering (DAF). Group 2 genes, WRKY9, BCKDH, KAS I, CaMYB31, HTC, KAS III and BCAT showed a higher expression in ‘Takanotsume’ under the 100 g·m^-2 P fertilizer treatment at 20 DAF. Group 3 comprised ACS, FAT and COMT, showed higher expression in at least one variety grown in 100 g·m^-2 P fertilizer at 30 DAF. The increased expression of groups 1, 2 and 3 genes induced increases in the pungency of chili peppers grown in 100 g·m^-2 P fertilizer.

The Thai rice variety Khao Dawk Mali 105 (KDML105) is the most important of the rice strains grown in Thailand. However, this can be planted only once a year during the rainy season due to several cultivation constraints. The flowering time (or heading date) is one of the most important agronomic traits of crops. The plants’ response to the flowering time is considered an aspect of their adaptation to climate change, which affects their yield potential. We conducted this study to (i) improve Thai rice varieties by giving them the ability to escape dehydration and (ii) contribute to a database and future rice breeding programs in unpredicTable conditions. Regarding the heading trait expression of F₂-hybrid plants, we observed that under the long-day conditions, both rice hybrid cultivars had 50% days to heading (DTH): at 105–125 days after sowing (DAS) in KDML105/IR24 and 110–125 DAS in IR24/KDML105. A F₃-phenotyping analysis revealed that KDML105/IR24 on lines 27, 36, and 73 and IR24/KDML105 on lines 7, 70, and 77 had low variations of DTH. These six lines are considered homozygous strains with a fixed heading period. In the genotyping of F₃, we observed that KDML/IR24 on lines 27, 69, 73, and 87, including the combination of IR24/KDML105 line 7, had the same expressions of Hd1 and Hd3a as IR24 (the parent plant) and did not express DTH8. Based on these data, these five lines can be used for future breeding programs.

Photosynthesis and dry matter production were examined to understand the growth response of sago palms to different nutrient levels. Seedlings were grown in the pots filled with soil with Kimura B culture solution at 100% (standard), 50%, and 10% strengths for 51 weeks. The total dry matter weight, total leaf area, chlorophyll content per unit leaf area, electron transport rate, N content per unit leaf area, petiole N concentration, and P content per unit leaf area were highest at 100% strength, followed by 50% and 10% strengths. The single leaflet area, and effective quantum yield of photosystem II [Y (II)] (at some light levels) were the highest at 100% strength, and their differences between the 50% and 10% strengths were not significant. The total leaflet number per leaf, emerged leaf number, and net photosynthetic rate were at the same level at the 100% and 50% strengths, the values of which were high as compared with those at the 10% strength. Sago palm growth was influenced by the supply of nutrients for about one year, and among three major elements, nitrogen was found to be the most influential. Phosphorus absorption and translocation were also affected, while K absorption and translocation were not restricted by a reduction in the application of nutrients. The restriction of nutrient supply proceeded with leaf morphogenesis such as leaflet area expansion and photochemical reaction process prior to the depression of new leaf formation and leaf gas exchange.