Genome analysis of Thinopyrum bessarabicum and T. elongatum

Thinopyrum bessarabicum (2n = 14; JJ) was successfully crossed with T. elongatum (2n = 14; EE) but the reciprocal cross failed. Five of the 19 F 1 plants headed in a greenhouse without being vernalized. Spikes of F 1 hybrids were intermediate to those of the parents for number of florets per spike, glume length, and the first rachis internode length, but similar to those of T. bessarabicum and T. elongatum for spike length and number of spikelets per spike, respectively. Karyotypes of mitotic chromosomes in the parental species revealed that three of the seven chromosomes in the J and E genomes were similar in length and arm ratio. Meiosis in the F 1 hybrids substantiated the conclusion from karyotype analysis that the other four chromosomes had undergone some structural rearrangements such as reciprocal translocation. Metaphase-I cells in hybrid plants averaged 2.68 I, 4.68 II, 0.27 III, 0.27 IV, and 0.01 V. Although 10% of the pollen grains were stainable with I 2 –KI, F 1 plants of T. bessarabicum × T. elongatum did not set seed upon selfing. It is concluded that the J and E genomes are so closely related that the E genome designation should be changed to J e . The evidence reported here supports the transfer of Lophopyrum elongatum to the genus Thinopyrum. Wheat breeders should be able to utilize the genes in T. bessarabicum as readily as those in T. elongatum.Key words: Genome, mitosis, meiosis, karyotype, idiogram, hybrid.