Stay-Green Panicle Branches Improve Processing Quality of Elite Rice Cultivars

File S1. Methods.

Rice materials and growth conditions

Rice plants were sown in a paddy field in Tianhe (23.2o N, 113.4o E), Guangzhou, China, in late 2019. Three biological replicates of rice panicle branches and grains at 8, 18, 23, and 30 d after flowering (DAF) were collected, frozen in liquid nitrogen, and stored at -80 oC.

Measurement of chlorophyll content

Chlorophyll was extracted from 0.45 g of panicle branch tissue (fresh weight), after which its content was determined by measuring the absorbance at 645 and 663 nm using a spectrophotometer (Thermo Fisher Scientific Corp. Waltham, MA, USA) (Kim et al, 2015).

Measurement of soluble sugar and starch content

The soluble sugar and starch contents of panicle branches and grains from different positions (apex and base) were measured using physiological assay kits (Suzhou Grace Biotechnology Co., Ltd, Jiangsu, China) according to the manufacturer’s instructions and based on anthrone colorimetric and enzymatic methods, respectively (Yuan et al, 2021). All processes were biologically and temporally repeated in three independent and parallel experiments.

Trait measurements

The grain length and width, chalky rice rate, chalkiness degree, amylose content, protein content, lipid content, gel consistency, and brown, milled, and head rice rates were measured using the NY/T593-2013 standards published by the Rice Product Quality Supervision and Inspection Center, Ministry of Agriculture, China (http://www.zbgb.org/27/StandardDetail 1476335.htm) (Hu et al, 2015).

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