Homeologous chromosome pairing in distant allohaploid hybrids of the genus Solanum

The pairing of chromosomes in meiosis of unique allohaploid hybrids obtained using the methods of somatic hybridization, in vitro androgensis and chromosome engineering has been studied. Hybrids from two combinations were analyzed: (1) between cultivated potato S. tuberosum (dihaploid, 2n = 2x = 24, AA genome) and wild species S. etuberosum (2n = 2x = 24, EE genome) and (2) between cultivated tomato S. lycopersicum (2n = 2x = 24, LL) and wild species S. etuberosum (2n = 2x = 24, EE). Subsequent application of chromosome-specific BAC-clones of potato and probes of differentially labeled total DNA of the parental species allowed to identify chromosomes which were involved in pairing and to detect their genomic identity. Up to 7 intergenomic bivalents per cell were observed in allohaploids between S. tuberosum and S. etuberosum (AE); the chiasmata were distributed in the distal regions of the long arms of each chromosome and in the short arms of chromosomes 3, 6, 11, and 12. Androgenic regenerants of somatic hybrids S. lycopersicum with S. etuberosum are characterized mainly by univalent meiosis; rare bivalents (from 0 to 2 per cell) are formed by homeologs of chromosomes 4 and 6. The prospects of the proposed approach are discussed for the application of somatic hybridization, in vitro androgensis and chromosome engineering to study the potential of homeologs pairing and the strategy of introgressive hybridization of remote plant species.