Identifying the environmental index
Environmental data were retrieved from the websites of the National
Oceanic and Atmospheric Administration (NOAA:
https://www.noaa.gov/weather) and the Astronomical Applications
Department of the US Naval Observatory
(https://www.usno.navy.mil/USNO/astronomical-applications). Daily
temperatures (°F) were converted to growing-degree days (GDDs) forB. napus with the formula: GDD = [(maximum temperature +
minimum temperature) / 2] – 37.4 (Marshall and Squire, 1996, Pullens
et al., 2019). The daily diurnal temperature range (DTR) was calculated
as Tmax – Tmin. Phenotypic data were
collected from 505 B. napus inbred lines planted in eight
environments (Supplementary Table S3), along with environmental data
(Supplementary Table S11) covering the entire growth period in these
eight environments. Three categories of environmental parameters were
tested: temperature (GDD and DTR), moisture (precipitation [PR] and
relative humidity [RH]) and light (clear sky photosynthetically
active radiation [CPAR] and ultraviolet B [UVB]) by implementing
the CERIS algorithm in R to identify environmental indices
(https://github.com/jmyu/CERIS_JGRA) (Li et al., 2018). The most
relevant environmental index in the three categories of environmental
parameters for SOC was separately chosen according to the highest
correlation between environmental means and environmental index within
the corresponding search window (Figs. 2b, S5).