4.4 Genetic understanding of waterlogging tolerance
Our results showed that most of
currently available Australia barley genotypes are intolerant to
waterlogging. It is thus crucial that further scientific endeavour is
undertaken to develop more waterlogging tolerant genotypes that
alleviate yield losses caused by waterlogging.
Our previous studies have identified QTL controlling root AF under
waterlogging stress, which is one of the major mechanisms for
waterlogging tolerance in barley (Zhang et al., 2016). This gene was
introgessed into a commercial variety Macquarie through repeated
backcrossing. Although we did not
measure AF (e.g. scored the proportion of aerenchyma based on digital
images), because this has been done in many previous studies (Zhang et
al., 2015; Zhang et al., 2016). Our results showed that Macquarie+ was
the most tolerant to waterlogging (Fig. 2a, b); this result was mainly a
consequence of higher numbers of spikes/m2 and to a
lesser extent maintenance of grain weight under waterlogging (Fig. 3).
Macquarie+ outperformed other varieties in most case and for most
waterlogging treatments. The QTL for AF mitigated around 23% yield loss
under waterlogging stress, suggesting that the QTL is effective in
improving waterlogging tolerance of commercial varieties and can be used
in breeding programs.