Comparative transcript abundance of gibberellin oxidases genes in two barley () genotypes with contrasting lodging resistance under different regimes of water deficit.

Barley (Hordeum vulgare ) is the world's fourth most important cereal crop, and is particularly well adapted to harsh environments. However, lodging is a major productivity constraint causing 13-65% yield losses. Gibberellic acid (GA) homeostatic genes such as HvGA20ox, HvGA3ox and HvGA2ox are responsible for changes in plant phenotype for height and internodal length that contribute towards lodging resistance. This study explored the expression of different HvGAox transcripts in two contrasting barley genotypes (5-GSBON-18, lodging resistant; and 5-GSBON-70, lodging sensitive), which were sown both under controlled (hydroponic, completely randomised factorial design) and field conditions (split-plot, completely randomised block design) with two irrigation treatments (normal with three irrigation events; and water deficit with one irrigation event). In the hydroponic experiment, expression analysis was performed on seedlings at 0, ¾, 1½, 3 and 6h after application of treatment. In the field experiment, leaf, shoot nodes and internodes were sampled. Downregulation of HvGA20ox.1 transcript and 2-fold upregulation of HvGA2ox.2 transcript were observed in 5-GSBON-18 under water deficit conditions. This genotype also showed a significant reduction in plant height (18-20%), lodging (<10%), and increased grain yield (15-18%) under stress. Utilisation of these transcripts in barley breeding has the potential to reduce plant height, lodging and increased grain yield.