Differential expression of the <i>shrunken‐2</i> ( <i>sh2</i> ) gene in super sweet corn inbred lines under water‐limited conditions

Abstract Drought stress severely limits corn production, particularly in arid and semi‐arid regions, where erratic climate continues to increase the frequency of water scarcity. Super sweet corn ( Zea mays L. var. saccharata ) is especially vulnerable due to its reduced starch reserves caused by mutations in the shrunken‐2 ( sh2 ) gene, which encodes the large subunit of ADP‐glucose pyrophosphorylase (AGPase), a key enzyme in starch biosynthesis. This study aimed to evaluate the expression of the sh2 gene under water‐limited conditions in two super sweet corn inbred lines recently incorporated into breeding programs: a drought‐tolerant line (MCH87002/19‐1) and a drought‐sensitive line (MCH87004/23‐1). The experiment was conducted in 2020 at the Khorasan Razavi Agricultural and Natural Resources Research and Education Center under controlled greenhouse conditions in Mashhad, Iran. Real‐time polymerase chain reaction revealed that water‐limited stress significantly downregulated sh2 expression in the drought‐tolerant line (0.63‐fold; p = 0.023), indicating a potential energy‐saving strategy under stress. This downregulation was associated with reduced AGPase activity and limited starch biosynthesis. Conversely, sh2 expression in the drought‐sensitive line remained unchanged (0.97‐fold; p = 0.892), suggesting a lack of transcriptional response to water‐limited conditions. These findings highlight the potential of sh2 as a molecular marker for breeding drought‐resilient super sweet corn. Integrating sh2 expression profiles into breeding programs could facilitate the development of genotypes that balance sugar content and stress adaptation, contributing to sweet corn productivity in semi‐arid environments.