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).