Fertility restoration of hybrids between Solanum melongena L. and S. aethiopicum L. Gilo Group by chromosome doubling and cytoplasmic effect on pollen fertility

Reproductive fertility traits were studied in the reciprocal hybrids of the eggplant (Solanum melongena L.) and S. aethiopicum L. Gilo Group, and in synthetic amphidiploids to discover whether fertility in these reciprocal hybrids was restored by chromosome doubling. Isozyme and RAPD analyses confirmed hybridity of the hybrids and amphidiploids. Analyses of chloroplast and mitochondrial DNAs confirmed that the cytoplasm of each of the hybrids and amphidiploids was from the maternal parent. Pollen sterility of S. melongena × S. aethiopicum Gilo Group [F1 (Mel × Aet)] was restored by chromosome doubling, while the reciprocal hybrid S. aethiopicum Gilo Group × S. melongena [F1 (Aet × Mel)] and its amphidiploid did not produce any pollen grains; their microspores degenerated without being released from tetrads. Hence the cytoplasm of S. aethiopicum Gilo Group seems to be responsible for their pollen-non-formation type sterility of the hybrid. Both the F1 hybrids did not set any fruits by either selfing or backcrossing, while their amphidiploids set fruits after pollinating with pollen from the amphidiploid of F1 (Mel × Aet). Seeds obtained from both the amphidiploids germinated normally. Chromosome doubling has been effective in restoring fertility of the hybrids.