(Fig. 1c).
NASSAR (1977) reported that eight wild Manihot species
including M. oligantha Pax and cassava itself had 2n
36. The same number was reported by CARVALHO and
GUERRA (2002). The polyploidized type of the hybrid
between M. esculenta and M. oligantha showed multivalent
formation ranging from three to four quadrivalents,
while the diploid type has formed regular bivalents in 17
of the normal 18 bivalents in cassava species. This is a
striking feature in an interspecifi c hybrid where univalents
are expected. The parent M. oligantha Pax used in hybridization
may have been a result of introgression. NASSAR
(1978) showed that the type used in crosses was not a pure
type since it differed from the original M. oligantha in leaf
type and edible root formation, characters which were
assumed to have been acquired from cassava, by natural
hybridization followed by subsequent introgressive
crosses in direction of M. oligantha.