Abstract:

In this study, we focus on the genetic mechanisms underlying culm strength in rice, aiming to provide a robust theoretical foundation for molecular breeding of lodging-resistant varieties. By systematically reviewing and conducting in-depth analyses of academic literature and research reports, we explore the regulatory mechanisms of genes associated with culm strength, culm chemical composition, hormonal regulation, and plant architecture, as well as their molecular mechanisms in conferring lodging resistance. Consequently, rice culm strength is influenced by both morphological traits (e.g., basal internode diameter and culm wall thickness) and chemical components (including cellulose, hemicellulose, and lignin contents). Notably, the mechanical properties of lower internodes are key determinants of rice lodging resistance. In terms of genetics, SCM3 (an allele of OsTB1) enhances culm strength via the strigolactone signaling pathway. WAK10 regulates cellulose synthesis in secondary cell walls. OsTCP19 facilitates the balance between lignin and cellulose. IPA1 achieves synergistic improvements in lodging resistance and yield by optimizing plant architecture—specifically, by reducing ineffective tillers, increasing culm diameter, and balancing lodging resistance with an increased number of grains per panicle. In terms of breeding applications, molecular marker-assisted selection has been employed to screen for quantitative trait loci (QTLs) associated with culm strength, such as prl5 and lrt5. Additionally, gene-editing technologies (e.g., CRISPR/Cas9) have been utilized to modify key genes governing culm strength in rice lodging resistance breeding. Through backcrossing to develop near-isogenic lines (NILs), multiple strong culm genes (including SCM1-4) have been pyramided—resulting in NIL-SCM1, NIL-SCM2, NIL-SCM3, NIL-SCM4, as well as double and triple NIL combinations. This approach has enabled the successful development of lodging-resistant varieties, namely 'Sakura Prince' and 'Monster Rice 1'. This study proposes that future work should be carried out in the following aspects: mining novel lodging resistance genes (e.g., the STRONG2 module) and analyzing multi-gene synergistic effects, establishing a genetic balance model involving stem strength, panicle weight, and panicle number, optimizing gene pyramiding strategies in combination with genome-wide association analysis, and exploring the impacts of environmental factors (such as typhoons and dense planting) on culm strength. These efforts aim to achieve enhancement of rice lodging resistance and yield simultaneously.

Key words: rice, culm strength, hormone regulation, breeding application