Recording of frost events and damage
Because of the differences in growth stages among individual plants and
between main spike and tillers, spring radiation frost impact can vary
significantly between heads. Therefore, precise frost tolerance
phenotyping poses a daunting task. In this study, six DH populations
were grown in three distinct environments. In total, two locations
comprising around 4,000 plots (about 4 ha) suffered from frost damage
during the most critical developmental stages. We adopted a visual
scoring method to estimate frost damage, commonly used by other
researchers (Tóth et al., 2003; Knox et al., 2008; Liu et al., 2014;
Sieber et al., 2016; Chen et al., 2019).The entire scoring was carried
out by a single person to minimise human biases. As a result, robust QTL
detection was achieved, as demonstrated by the same QTL regions showing
up consistently in multiple environments and across populations. To
further validate our frost scoring, five parental and control lines
covering three anthesis windows were used to assess the frost damage
using a different scoring method based on floret sterility (Reinheimer
et al., 2004; Biddulph et al., 2013). Between 70 to 140 spikes from 7 to
14 randomly selected plots from each line were assessed at the Muresk
site, with the results showing the same damage pattern as in our visual
scoring.