In order to determine the physical characteristics of the best substrate for germinating Dioscorea rotundata minisetts, a multifactorial trial was carried out on three sawdusts in a randomized complete block design with four replicates for 1440 minisetts, 480 for each of the proximal, distal and medial parts. Two criteria were used to characterize the three sawdusts: particle number and water retention capacity. The germination parameters (of the different parts of the mother tubers sown in these three sawdusts), i.e. the rate, speed, time and duration of germination of the minifragments, made it possible to better discriminate between them. It emerged that sawdust 2, with a particle index of (3 ± 1) and an average water retention capacity of (254.01 ± 14.43) l/m3, was the best substrate of the three sawdusts. It had an average germination rate of (98.33 ± 0.43) %, an average germination rate of (2.22 ± 0.13) minisetts/day, a germination time of (4.0 ± 0.0) days and an average germination duration of 6 days, all of these parameters being superior to those of the other two sawdusts. These observations show that any substrate with a particle number of 3 and a water retention capacity of sawdust 2 is suitable for the germination of any mother tuber fragment.

Keywords: germination rate, germination speed, germination time, particle index, substrate, water retention index