Cytomorphological analysis of a novel hybrid from Solanum melongena 'Golden' x S. scabrum 'Scabrum' (Solanaceae)

Abstract

Genotype manipulation through the introduction of novel genes for improved yield, agronomic qualities and a larger gene pool informed an experimental cross between diploid Solanum melongena 'Golden' (2n = 2x = 24) and tetraploid S. scabrum 'Scabrum' (2n = 4x = 48). The F1 fruit contained eight seeds which had a 100% germination and a chromosome number 2n = 6x = 72. Surviving hybrids were closer to the diploid parent in many characters. Leaves were fairly lobed, sparsely hairy and were 13.5 x 8.6 cm in the hybrid compared to the hairy, deeply lobed, 14.8 x 10.6 cm leaves in the diploid and glabrous, entire and 11.4 x 10.6 cm leaves in the tetraploid parent. The inflorescence in the hybrid was a raceme as in the diploid parent but was umbellate in the tetraploid. Pollen viability was 38.2% in the hybrid but was 71% and 97.4% in the diploid and tetraploid parents, respectively. Fruit was seedless in the F2; it was round and red, containing 384 seeds, globose-shaped, yellow seeds in the diploid, and 67, round, purple seeds in the tetraploid parent. Meiosis was regular in the hybrid with few univalents and impaired bivalents due to dissimilar parental genomes. Mitotic chromosomes were asymmetrical with various sizes. Epistasis and negative gene interaction mechanisms were implicated in the hybrids' low quality and breakdown. Backcross to the tetraploid parent may bring about gene recombination and allelic realignment for desirable phenotypes in the F2 and subsequent generations. Endoduplication of the triploid zygote might have produced an autoallohexaploid hybrid.