New intergeneric diploid hybrids among Agropyron, Thinopyrum, Pseudoroegneria, Psathyrostachys, Hordeum, and Secale
Eight diploid intergeneric hybrids representing six genomic combinations were synthesized and meiotically analyzed. The SN hybrids of Pseudoroegneria spicata and P. spicata spp. inermis with Psathyrostachys juncea resembled the Pseudoroegneria species in that the spikes had a single spikelet per node. The spikes of all other hybrids were intermediate to those of their respective parents. The mean meiotic pairing pattern for two SN hybrids was 9.90 I + 1.74 rod II + 0.16 ring II + 0.07 III + 0.02 IV, which was equivalent to a mean arm-pairing frequency (c) of 0.16. When the results were averaged with a previously reported hybrid, the mean pairing in two hybrid plants of P. spicata × Thinopyrum bessarabicum (SJ genome combination) was 4.79 I + 3.24 rod II + 0.91 ring II + 0.18 III + 0.09 IV and c = 0.41. Of the JeS hybrids, mean pairing was 8.40 I + 2.30 rod II + 0.25 ring II + 0.13 III + 0.03 IV (c = 0.28) for T. elongatum × P. spicata and 6.98 I + 2.90 rod II + 0.39 ring II + 0.12 III + 0.02 IV (c = 0.28) for T. elongatum × P. spicata ssp. inermis. The JP hybrid of T. bessarabicum × Agropyron cristatum had 8.99 I + 2.11 rod II + 0.14 ring II + 0.13 III + 0.03 IV and c = 0.20. Pairing was lower in the new PH hybrids A. mongolicum × Hordeum californicum and HR hybrids H. californicum × Secale montanum: 12.20 I + 0.82 rod II + 0.05 III (c = 0.06) and 13.04 I + 0.44 rod II + 0.01 III (c = 0.03), respectively. These data contribute to the elucidation of the genomic relationships among diploid species of the perennial Triticeae.Key words: hybrid, genome, chromosome pairing, Triticeae.