Increased grain weight conferred by GW2 mutations in wheat does not translate into yield gains in multi-year field trials of near-isogenic lines.

Mutations in TaGW2 increase grain weight by up to 20% in wheat but do not improve overall yield in multi-year field trials.

• Why it matters: Understanding whether genetic modifications that enhance grain size translate into higher yields is crucial for wheat breeding and food security. Despite consistent effects on grain weight, the impact on total yield remains uncertain, highlighting a gap between laboratory findings and field performance.
• What they did: Researchers evaluated TaGW2 mutants in hexaploid wheat across 12 field trials using near-isogenic lines, different sowing densities, and semi-dwarfing backgrounds, focusing on grain weight, grain number, and yield components.
• The result: While certain mutants, like the aabbdd triple mutant, increased thousand grain weight by approximately 20%, overall grain yield was unchanged or slightly reduced due to fewer grains per spike, indicating limited yield gains primarily from reduced spike number rather than spike productivity.