Intergeneric Hybrids between Aegilops squarrosa and Secale cereale and their Meiotic Chromosome Behaviour

Three hybrid plants with different combinations of D and R genomes were produced from crosses between Aegilops squarrosa (2×: and 4×) and Secale cereale (2× and 4×) using embryo culture. Production frequencies of mature hybrids, having the genomes DR, DDR and DDRR, were 2.0%, 5.2% and 2.2 %, respectively, of florets pollinated. Amphidiploids were obtained directly from the cross between tetraploid parents. The majority of their morphological features were intermediate between those of the parents but, as with rye, the rachis was tough. Diploid and triploid hybrids were completely seed-sterile, whereas the amphidiploid had an average self-fertility of 4.5 % with a range of 0 to 45 %. The somatic chromosome numbers of diploids, triploids and amphidiploids were 2n = 14, 21 and 28, respectively. At meiotic metaphase I, the mean chromosome associations were 0.01 III + 0.26 II + 13.4 I in diploids, 6.96 II + 7.1 I in triploids, and 10.5 II + 7.9 I in amphidiploids. In diploids, pairing between D and R chromosomes was observed in the form of end-to-end types without chiasmata. Homologous pairing between D chromosomes was predominant in plants having two sets of D genomes. Amphidiploids showed a diploid-like chromosome behaviour. Homoeologous pairing was not observed in either triploids or amphidiploids.