THESIS

2. Genetic relationships of Solanum spp. using interspecific hybridization
The degree of hybridization varied with in each combination. Among 169
cross combinations, seventy-three of them were crossable. Percentages of fruit setting
ranged from 0 to 98.3. The highest percentages of fruit setting (98.3) were found in
the cross between S. villosum (TS02600) and S. americanum (S00861) (Table 18).
However, this is due to the low number of pollinated flowers (58 pollinated flowers;
Table 18). In addition, very low fruit setting was observed in many crosses of
different species. This result indicates the level of cross compatibility depending on
the varieties used and/or on environmental conditions. Furthermore, the reciprocal
differences in the success of crosses are common and the frequency of abortion hybrid
seed is also high (Table 15 and 18).
1) Cross - compatibility of S. melongena and its wild relatives (S. torvum, S.
americanum, S. villosum and S. nigrum)
When S. melongena was used as a female parent, the percentages of fruit
setting is higher on the intraspecific hybridization within S. melongena (96.2 %) than
interspecific hybridization between S. melongena and its wild relatives (Table 14 and
15). Percentages of fruit setting between S. melongena x S. torvum range from 0 to 72
(Table 14). The highest percentages of fruit setting (72 %), was found in the cross
between S00022 (collected in India) and S00429 (collected in Thailand), but no plants
were obtained even after embryo recuing. They had only the abnormal seedlings
(Figure 11).
However, the crosses between S. melongena (S00625 collected in South
Africa) x S. torvum (S00429) and S00809 (collected in Bangladesh) and S00429
could be successful through embryo rescue (Figure 10). In addition, S00625 x S00429
was better than S00809 x S00429 (Table 15). This resulted in the effect of genotype
and geographical areas or may be due to variation in environmental conditions (Rao
and Rao, 1984).
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