Root development of fibrous and storage roots of cassava (Manihot esculenta Crantz, TMEB419) were monitored over time by destructive sampling. Tissues of fibrous roots, storage roots, sink and source leaves were taken 30, 34, 38, 42, 52, 60 and 68 days after planting (dap). Samples of 30, 38 and 60 dap were sequenced in biological triplicates for total RNA.. Cassava Root Bulking

Despite the importance of storage roots (SR) organs for root crop yield, origin and development of cassava is poorly understood. Here we use multiple approaches to shed light on the initial stages of root development demonstrating that SR and fibrous roots (FR) follow different rhizogenic processes. Transcriptome analysis carried out on roots collected before, during, and after root bulking, highlighted early and specific activation of a number of functions essential for root swelling and identified root-specific genes able to effectively discriminate emerging FR and SR. Starch and sugars start to accumulate at higher rate in SR before they swell but only after parenchyma tissue has been produced. Finally, using non-destructive computed tomography measurements, we show that SR (and no FR) contain an inner channel structure in continuity with the stem secondary xylem that indicates the possible distinct rhizogenic process of SR.