Advances in Genes Associated with Straw Degradation in Rice

Rice (Oryza sativa L.) generates approximately 300 million tons of straw annually worldwide, and efficient degradation and valorization remain critical bottlenecks for sustainable agriculture. Straw degradability is fundamentally constrained by cell wall recalcitrance, which is determined by the composition and architecture of cellulose, hemicellulose, and lignin, each under genetic regulation. This review proposes a three-parameter analytical framework, including cellulose crystallinity, hemicellulose side-chain modification, and lignin monomer composition and cross-linking density, to systematically assess the regulatory role of endogenous rice genes in straw degradability. We provide a comprehensive synthesis of recent advances in cellulose synthase genes and brittle culm mutants, lignin biosynthesis, cell wall modification genes, and the integration of genetic mapping with molecular breeding strategies. Particular attention is given to the trade-offs between enhanced degradability and agronomic performance, and to emerging strategies, including semi-dominant alleles, tissue-specific promoters, and multi-gene pyramiding, which hold potential for resolving these trade-offs. We conclude by identifying key research gaps and proposing future directions for developing dual-purpose rice cultivars with both high grain yield and superior straw degradability.