THESIS

3) Cross - compatibility among S. americanum, S. villosum and S. nigrum
These cross combinations among S. americanum, S. villosum and S.
nigrum were successfull in both directions. This indicates that they are closely related
which support the former classification that place them together in Solanum nigrum
Complex (Edmonds and Chweya, 1997). However, the percentages of fruit setting
vary among different species combinations. Some crosses produced fruit with viable
seeds and some others produced aborted seed (Figure 9).
When S. americanum was used as female parent, the crossing of
accessions within S. americanum produced fruit with viable seeds and hybrid plant.
The percentage of fruit setting varies among accessions. This result showed the effect
of genotype and phylogenic relationship on cross compatibility (Hawtin et al., 1997).
S. villosum (S00860 from Japan) is crossable with all accessions of S. americanum
and hybrid seeds were obtained. The crosses between S. americanum x S. nigrum and
their reciprocals gave hybrid fruits but the percentages of fruit setting, when using S.
americanum as female parent, was lower than the respective reciprocal. This finding
is in contrast to the result obtained by Ganapathi and Rao (1986) who found that the
crosses between S. nigrum (2n = 6x = 72) and S. americanum (2n = 2x = 24) were
successful only when S. nigrum was used as female parent.
When S. villosum was used as female parent, the crossing of accessions
within S. villosum produced fruit with viable seeds and hybrid plant. All accession of
S. villosum is crossable with S. americanum. The percentage of fruit setting is highest
(98.3 %) from crossing between the accessions TS02600 (S. villosum) x S00861 (S.
americanum) (Table 18). Similar to Beg et al. (1989) who studied the biosystematic
of S. villosum subsp. puniceum (n = 24) and S. americanum (n = 12) in which the
interspecific hybrids (n = 18) were obtained using S. villosum as the female parent.
The fruits were obtained from the crosses between S. villosum and S.
nigrum, but no hybrid plant was obtained due to the abortive hybrid seeds. Similar to
Beg and Khan (1988) who reported that tetraploid S. villosum subsp. puniceum (2n =
82