Genome-Wide Association Study Identifies OsWRKY102 as a Positive Regulator of Culm Mechanical Strength in Rice

Lodging is a major constraint to rice productivity and grain quality. The mechanical strength of basal internodes, particularly bending resistance (BDR), is a critical determinant of lodging resistance. In this study, we evaluated the BDR of the third and fourth basal internodes (BDR3 and BDR4) in a diverse panel of 340 rice accessions. A genome-wide association study (GWAS) identified three QTLs significantly associated with BDR3, which were defined and designated as qBDR1, qBDR4, and qBDR5. Further analysis revealed that OsWRKY102 on qBDR1 was identified as a key candidate gene. Haplotype analysis revealed distinct allelic variations between subspecies, with the elite haplotypes (Hap.1 and Hap.4) contributing to superior lodging resistance, while Hap.2 was predominantly found in lodging-susceptible Japonica accessions. CRISPR/Cas9-mediated knockout of OsWRKY102 in the ZH11 background resulted in a significant reduction of more than 50% in both BDR3 and BDR4 compared to the wild type. Detailed phenotypic characterization of the oswrky102 mutants revealed a substantial decrease in cellulose content and culm diameter, accompanied by an increase in culm wall thickness. These findings demonstrate that OsWRKY102 maintains culm mechanical strength by promoting radial expansion and cellulose accumulation. Biomechanical analysis further suggests that culm diameter and cellulose content are more critical for bending strength than wall thickness. Our results elucidate the regulatory role of OsWRKY102 in coordinating culm morphology and cell wall composition, providing a valuable genetic target for molecular breeding of high-yielding, lodging-resistant rice varieties.