Decoding Lodging Resistance in Elite Chinese Conventional Rice Varieties: A Phenotypic and Biomechanical Perspective

The lodging resistance of rice is a prerequisite for ensuring yield and rice quality. An in-depth analysis of key traits affecting rice lodging resistance is crucial for guiding the cultivation of excellent rice varieties and field production. Given consumer demand for high-quality rice and frequent extreme weather conditions, this study focused on six high-quality conventional rice varieties and compared the main stem internode physical traits, stem and sheath plumpness traits, main stem mechanical properties, yield-related traits, and panicle characteristics of the plants based on field phenotype measurements. Among them, three varieties showed lodging resistance in the field, while the other three varieties all experienced varying degrees of lodging susceptibility. The results showed that lodging-resistant varieties exhibited a more reasonable internode structure, lower plant height, gravity center height, and relative gravity center height, as well as shorter and thicker second internodes (N2). Additionally, they had higher sheath phimosis degree, greater bending stress, internode-breaking moment, and plant-breaking moment, along with a lower lodging index compared to lodging-susceptible varieties. Specifically, lodging-resistant varieties had 0.83-9.61% lower plant height, 4.11-16.10% lower gravity center height, and 0.09-12.68% lower relative gravity center height than those of lodging-susceptible varieties. Their N2 internode length was 8.96-44.69% shorter, while stem and sheath weight ratios were 16.37-268.58% and 8.27-165.01% higher than those of lodging-susceptible varieties, respectively. At the same time, lodging-resistant varieties exhibit the ability to stabilize yield while reducing their own risk of lodging by increasing effective panicles and reducing single panicle weight. In addition, NX42, LD3, and SY17 were ultimately evaluated as low-risk lodging varieties in this study. This study aims to address the lodging problem of high-quality conventional rice and analyze the key mechanisms underlying its lodging resistance. The research provides important theoretical support for genetic improvement of high-quality conventional rice.