Tuber shape (Figs. 13 and 14). On the same tubers where the skin color has been read, note the general shape of the tubers, which corresponds to the first digit; the ratio of tuber diameter to tuber length delimits the general shapes: When the diameter (D) is greater than the length (L)of the tuber (distance between the base and the apex of the tuber), i.e. D>L, it is the compressed shape; when the diameter is similar in all directions D≈L, it is the round shape; when the ratio of the length of the tuber and its diameter is between L1:D1 (quadrilateral) to L1.5:D1, it is oblong shape; when the ratio is between L1.5:D1 to L3:D1, it is an elongated oblong shape and when the ratio is higher, L>3:D1, it is an elongated shape; when the diameter is variable in the same tubercle, that is to say, they present almost triangular shapes, we have two alternatives: if D is narrow towards the apex and wider towards the base, we have the oval shape; if on the contrary the diameter of the apical part is greater than that of the base of the tuber, we have the ovate shape; if the diameters both towards the base and towards the apex decrease rapidly, we have the elliptical shape. Continue with the determination of the absence or presence of shape variants or unusual shapes (Fig. 14) that generates the second digit; accompany with the evaluation of the depth of eyes of the same tubers, gives rise to the third digit