Origin of Sv genome of Aegilops variabilis and utilization of the Sv as analyser of the S genome of the Aegilops species in the Sitopsis section

Hybrids of Aegilops variabilis (2n = 28, UUSvSv) with the low‐pairing type lines of Ae. longissima, Ae. bicornis, Ae. searsii, Ae. speltoides and Ae. umbellulata were obtained. This is the first report of successful hybridization between Ae. variabilis and Ae. searsii. Meiotic analysis of these hybrids showed that the U genome of Ae. variabilis donated by Ae. umbelltilata remained nearly unchanged and Ae. longissima is the possible donor species of the S genome to Ae. variabilis. But the Sv genome and the S1 genome of Ae. longissima are not completely homologous and are structurally differentiated by at least one interchange. According to their levels of homology with Sv through the means of chromosome associations, the four genomes of Sitopsis section species can be classified as follow: Sv≃ S1 > Sb > Ss > S. The meiotic behaviour of the hybrids between the wheat ‘Chinese Spring’ and the four Sitopsis section species studied has not supported the view that one of the four species is the donor of the B genome of wheat.