2.1. Rice materials
Twenty rice accessions (O. sativa L.) used for this study, including
cultivars, germplasm lines, and landraces from 10 geographical
areas, were introduced from the OryzaSNP project (http://www.
oryzasnp.org/) (McNally et al., 2009). All the 20 rice accessions
were planted in a randomized block design with two replications
in 2 years at the same site in Lingshui, Hainan province, China.
Each accession in the fields was planted into ten rows with six
plants per row. The seeds were sowed in early December 2010
and 2011, and harvested in April 2011 and 2012, respectively.
Hereafter 2 years (environments) are denoted 2011 and 2012 for
when the grain was harvested. Field management followed conventional
practices including nutrient and pest control procedures
to ensure the production in the field. The major environmental
conditions, i.e. the mean temperature, total radiation hours and
total rainfall for each month during rice growth periods were
reported previously (Tong et al., 2014).
The grains were air-dried to a moisture content of about 12%,
stored at room temperature for two months and later at 4 C in
the dark until all the grain materials were obtained. The samples
were dehusked on a Satake Rice Machine (Satake Co., Tokyo,
Japan) and the brown rice samples were ground to flours, which
were used for further analyses