Characterization of the Brittle Culm 1 in hexaploid wheat reveals potential for enhanced biomass utilization

Plant mechanical strength is essential for lodging resistance and biomass utilization. In this study, we isolated a brittle culm ( bc1 ) mutant in hexaploid wheat and identified the causal gene TaBC1 through map-based cloning. TaBC1 , a homolog of rice OsBC6 , encodes the cellulose synthase catalytic subunit 9. A single-nucleotide substitution (C>T) resulting in a Thr834Ile change within the third transmembrane domain was detected in bc1 mutant. Sequence analysis showed that this mutation site is highly conserved among 26 members of the TaCesA family and across both monocots and dicots. The bc1 mutant exhibits reduced mechanical strength, cell wall thickness, cellulose content, cellulose crystallinity, and D -fructose levels, while increasing lignin and total sugar content. TaBC1 is predominantly expressed in culms, with no significant expression difference between wild type and bc1 mutant. Furthermore, RNA-seq analysis revealed differentially expressed genes enriched in cellular and transmembrane component categories. This study firstly reports a brittle culm mutant in hexaploid wheat showing improved sugar release potential, offering applied insights for breeding wheat with enhanced biomass and lodging resistance. • This study firstly identified and characterized of a brittle culm ( bc1 ) mutant in hexaploid wheat. • A comprehensive multi-level phenotypic analysis was conducted, including mechanical, anatomical, biochemical, and transcriptomic evaluations of bc1 mutant. • Map-based cloning revealed that the gene BC1 encoded the cellulose synthase catalytic subunit 9. • The bc1 mutant exhibits normal morphology and growth, making it suitable for breeding applications without major agronomic penalties. • The mutant displays significantly reduced cellulose crystallinity and enhanced sugar release from straw, highlighting its potential for biomass utilization.