The relationship between GABA content and desiccation tolerance at five developmental stages of wheat (Triticum...

Drying wheat (Triticum durum ) seeds within their spikes may improve the seed desiccation tolerance. This study aimed to understand the effect of drying wheat seeds within their spikes on their desiccation tolerance in association with GABA (γ-aminobutyric acid) content, malondialdehyde (MDA), the expression of three dehydrin genes (dhn , wcor , dreb ) during seed development. Seeds of wheat variety 'Hourani-Nawawi' were harvested at five developmental stages: (1) milk (ML); (2) soft dough (SD); (3) hard dough (HD); (4) physiological maturity (PM); and (5) harvest maturity (HM) and dried either attached to or detached from their spikes. Drying the seeds attached to their spikes improved desiccation tolerance, speed of germination, and seedling length at ML stage. Before drying (freshly harvested), the seeds harvested at ML and HM had higher GABA than those at SD, HD, and PM. The attached-dried seeds had higher GABA content from ML to PM than at HM, and higher glutamate content at ML, SD, and HD than at the PM stage. Detached-dried seeds had the highest alanine at ML and PM. Attached-dried seeds had lower MDA than detached-dried seeds. Expression of dhn was highest in freshly-harvested and attached-dried seeds at SD. Highest expression of wcor in the attached-dried seeds was detected at SD and HM. Drying the seeds within their spikes increased the expression of dreb gene compared with the freshly-harvested seeds, except at the HD stage. In conclusion, drying the seeds within their spikes enhanced seed germination in association with higher GABA, lower MDA, and higher gene expression.