Abstract: Lodging-resistant capacity is vital for maintaining rice productivity. The current study obtained eleven brittle culm mutants via heavy ion irradiation on a rice cultivar ‘Wuyunjing 7’. The effects of stem cell wall components on bending strength and tensile stress of wild type rice and its brittle stem mutants at maturity stage were studied. It aimed to provide some theoretical supports for breeding lodging-resistant rice cultivars. The results showed that the cellulose content in stem cell wall of brittle culm mutants was 4.45%-33.63% lower than that of the wild type. The hemicellulose content in stem cell wall of brittle culm mutants was 19.80%-37.88% greater than that of the wild type. There was a significant positive correlation between stem bending strength and cellulose content (R=0.9342). The correlation coefficients of tensile stress and cellulose content for the first to fourth internodes were R1 =0.8475, R2=0.9212, R3=0.8791, and R4 =0.9203, respectively. There was no significant correlation between tensile stress and the content of hemicellulose and lignin. The findings indicated that the mechanical properties of stem brittleness were mainly decided by cellulose in the stem cell wall.

Key words: brittle culm mutant, stalk, cell wall components, bending strength, tensile stress