Polyploidy, genome composition, and dynamic gene regulatory coordination underpin low nitrogen tolerance in synthetic tetraploid wheats

The objective of this study was to identify synthetic tetraploid wheats (STW) with tolerance to low nitrogen (LN) stress. We compared two STWs (S^shS^shA^mA^m and S^lS^lAA), their diploid parents, and natural tetraploid wheat (NTW) under normal and LN conditions. One excelled in early-stage LN resilience via root growth plasticity and efficient N uptake, while the other showed superior late-stage tolerance via photosynthetic retention and increased N storage. S-subgenome-encoded NPF/NRT2 transporter genes under LN stress may act as drivers of LN adaptation. In contrast, NTW showed a yield-stress tradeoff under LN. There is a possibility of boosting LN resilience in wheat breeding by targeting the S-subgenome of STWs.