Comparative analysis of supplemental irrigation effects on structure and digestion of normal and amylose-only barley starches

To investigate the effects of supplemental irrigation (SI) on yield and starch quality in barley with different genotypes, a normal barley cultivar (NB) and an amylose-only mutant (AO) were cultivated under well-watered (WW) and SI conditions. Compared to WW, SI reduced grain yield by 1-4 % and starch content by 2-5 % in both genotypes, with a more pronounced reduction observed in NB than in AO. SI decreased photosynthetic capacity in NB but enhanced it in AO, consistent with observed differences in starch granule abundance in leaf tissues. SI increased the proportion of amylopectin long chains with degree of polymerization (DP) > 36 in NB, while elevating amylose short chains with DP ≤ 24 in AO. In addition, SI led to upregulation of starch synthase IIa (SSIIa) in NB and downregulation of starch synthase I (SSI) and SSIIa in AO. SI also enhanced the content of rapidly digestible starch in NB by 3 % but slowly digestible starch in AO by 4.5 %. These findings indicated genotype-specific responses of barley to SI, providing novel insights into the impact of SI on yield and starch functionality across different barley genotypes.