Foliar Silicon Application Regulates 2-Acetyl-1-Pyrroline Enrichment and Improves Physio-morphological Responses and Yield Attributes in Thai Jasmine Rice

Silicon (Si) deficiency is one of the most important issues, especially in rice crop. Foliar Si application in rice production is an alternative way to quickly improve not only grain yield but also aroma quality (2-acetyl-1-pyrroline; 2-AP), especially in Thai jasmine rice. The objective of this study was to assess the potential of exogenous application Si as foliar spray in regulating 2-acetyl-1-pyrroline (2-AP) content in KDML105 and RD6 rice grain and in improving yield traits. Overall, growth characters were retained in KDML105, whereas shoot height (14.9 % over the control) and leaf length (23.4 % over the control) of RD6 treated with 2 % Si were significantly reduced. Leaf greenness (SPAD), normalized difference vegetation index (NDVI) and net photosynthetic rate (Pn) of KDML105 were greater than those in RD6, in relation to EVI (enhanced vegetation index), GNDVI (green normalized difference vegetation index), NDVI and OSAVI (optimized soil adjusted vegetation index) detection by UAV sensors. Vegetation indices, GNDVI, OSAVI and EVI exhibited close relation with SPAD (R2 = 0.896), shoot height (R2 = 0.4406) and aboveground biomass (R2 = 0.7791), respectively. Si concentration in flag leaf tissues of KDML105 peaked (1.14 mg g−1 DW) when treated with 2 % Si, whereas it exhibited 1.6 folds increase in rice husk (0.75 mg g−1 DW; R2 = 0.5266) over the control. The content of 2-AP in KDML105 was higher compared with RD6 and was enhanced by 2 % Si treatment (1.39 folds over the control). Yield traits in KDML105 including panicle weight, grain fertility percentage, number of panicles per m2, total grain weight and harvest index (HI) were significantly increased by 2 % Si foliar application over the control. Based on the results, Si foliar application is effective in improving grain yield and in regulating 2-AP aromatic content, which further needs to be tested for temporal variations across locations.