For all varieties and both crops (without and with initial water stress) the highest root yield was attained at 12 months (Table 2). Nevertheless, a more dominant influence on root yield was that of water stress and this was evident at all harvest times
and for all varieties.
Root yield of cassava from the crop with initial water stress was significantly lower
than that of the crop without initial water stress (PB0.05).
Comparisons between the varieties revealed differences in drought tolerance, CMR 33-
57-81 having the highest root yield at all harvest times regardless of growth condition. Subjecting the plants to water stress conditions early in their development also significantly influenced starch content (PB0.05, Table 2).
Under such conditions the roots contained a significantly lower starch content (only 1.2–3.5% at 6 months, Table 2) compared to those grown without initial water
stress (20.4–25.9% at 6 months, Table 2).
This is in agreement with previous findings showing that when plants are subjected to water limiting conditions early in their establishment, root development is poor.
The roots show signs of retarded development and tend to be immature (Pardales and
Esquibel, 1996).