ANEUPLOIDS FROM TRIPLOID-DIPLOID CROSSES IN THE SERIESTUBEROSAOF THE GENUSSOLANUM

Abstract

Triploid-diploid crosses yielded nearly 75% aneuploid progeny. Of these, 60% were trisomics (2n = 25) and the rest ranged from 2n = 26 to 2n = 29. The most productive parents were those involving triploid S. maglia and diploid S. berthaultii. The initial trisomics often were not morphologically distinguishable from diploid sibs. Distinctive characteristics – such as slow growth; small, compact habit; lack of interstitial leaflets; and a bilobed stigma — were apparent in the backcross progenies. Most of the trisomics were fertile enough to be used in further genetic studies. Transmission of the extra chromosome through the female for three trisomics was 20–24%. Only primary trisomics were expected but meiotic study of seven clones indicated that all were secondary trisomics. The isochromosome may have originated from the tetraploids involved in the formation of the triploid clones or have been produced during meiosis of the triploid parent.