Relationship between cellulose accumulation and lodging resistance in the stem of relay intercropped soybean [Glycine max (L.) Merr.]

Stem lodging is the most important constraint for soybean at seedling stage in maize-soybean intercropping in China. This study was conducted to determine whether cellulose accumulation and lodging resistance of soybean was affected by different cropping systems and soybean varieties with different shading tolerance at seedling stage. Three soybean varieties - Nandou 032-4 (shade susceptible), Jiuyuehuang (moderately shade tolerant) and Nandou 12 (shade tolerant) - were used to investigate the effect of intercropping on soybean lodging behavior and cellulose accumulation in stems and its relationship to lodging resistance. Shading by maize significantly reduced cellulose accumulation and the stem breaking strength of the soybean, which were significantly negatively correlated with the lodging rate. In the maize-soybean intercropping system, shading inhibited sucrose transportation and degradation into cellulose in the soybean stem. Less content of cellulose in soybean stem at the seedling stage resulted in lodging in the intercropping system. Compared with shade susceptible varieties, Nandou 12 had higher cellulose accumulation and related enzyme activities in the stem, and thus the stem breaking strength and lodging resistance of the basal stem increased. The higher activities of sucrose phosphate synthase and sucrose synthetase in the stem were associated with shade tolerance and lodging resistance. Thus, we concluded that the high physical strength and high cellulose contents of the stem of shade tolerant soybean reduced the rate of lodging in the maize-soybean intercropping system.