Cellulose and Lignin Contents are Negatively Correlated with Starch Accumulation, and Their Correlation Characteristics Vary Across Cassava Varieties

Cassava storage roots contain large amounts of starch and low amounts of cellulose and lignin. However, the relationship between lignification with cellulose and starch accumulation during storage root development is not well understood. In the present study, the dynamic changes in starch, lignin, and cellulose contents as well as in root diameter, enzyme activities, and histochemical staining in the storage roots of six cassava varieties at different growth stages were assessed. The results revealed a negative correlation between the biosynthetic carbon allocation of starch and lignin ( r = − 0.780, p < 0.0001) and that of starch and cellulose ( r = − 0.873, p < 0.0001). Early and rapid formation of vascular tissue resulted in an increase in starch content in the six varieties and a transition of carbon flow from xylem development to starch formation at 100 days after planting was identified. Vascular vessels, cellulose, and starch exhibited a dynamic balance independent of cassava varieties. A more rapid decline in starch content was observed with increasing cellulose and lignin contents in high-starch varieties than that in low-starch varieties. This indicated that the optimal dynamic transition between structural and storage components during root development facilitates the formation of large amounts of starch in the parenchymal tissue. The fine regulation of lignification in cassava storage roots provides a potential strategy for breeding starch-rich cassava varieties.