HYBRIDS BETWEEN HORDEUM-VULGARE AND TETRAPLOID, HEXAPLOID, AND OCTOPLOID TRITORDEUMS (AMPHIPLOID HORDEUM-CHILENSE X TRITICUM SPP)

Crosses between Hordeum vulgare (2n = 2x = 14; (HHv)-H-v) and tetraplo id (2n = 4x = 28; (HHDD)-H-ch-D-ch), hexaploid (2n = 6x = 42; H(ch)H(c h)AABB), and octoploid (2n = 8x = 56; H(ch)H(ch)AABBDD) x Tritordeum a mphiploids have been carried out. The hybrid plants produced had the e xpected chromosome numbers, 2n = 3x = 21 ((HHD)-H-v-D-ch), 2n = 4x = 2 8 (H(v)H(ch)AB), and 2n = 5x = 35 (H(v)H(ch)ABD), respectively. The am phiploid between H. vulgare and hexaploid tritordeum was obtained by i n vitro immature inflorescence culture of the H(v)H(ch)AB hybrid. The amphiploid was sterile and no seed-set was obtained after backcrossing with hexaploid tritordeum. However, one plant with 38 chromosomes was obtained after backcrossing with durum wheat. Meiotic studies at meta phase I of the three hybrids showed a higher frequency of pairing in t he (HHD)-H-v-D-ch hybrid. Because of the presence of only one wheat ge nome and the absence of the B genome, the observed bivalents could be due either to homoeologous Hordeum chromosome pairing or homologous pa iring between duplicated chromosomes as a result of chromosome instabi lity.