| The origin of B genome in wheat has been the subject of intensive research by many wheat geneticisits. However, it has not been clarified till now, although it was speculated that the putative B genome donors were mainly focused on the five Aegilops species: Aegilops speltoides, Aegilops lgissima, Aegilops bicornis, Aegilops searssi, and Aegilops sharonensis.With the aim of unveiling the origin of B genome in wheat, or at least providing some molecular evidences for this issue, we investigated Triticum dicoccoides Triticum dicoccum and Triticum aestivum (Chinese Spring) and the five putitive donors of the wheat B genome (Aegilops speltoides, Aegilops longissima, Aegilops shonensis, Aegilops bicornis, Aegilops searssi) in Sitopsis section, together with Aegilops squarrosa, Triticum monococcum and Triticum urartu as negative control, by using SSR (simple sequence repeats) and RFLP (restriction fragment length polymorphism) markers,In the present study, 41 out of 117 pairs of SSR primers, and 20 RFLP probes were selected, all of which are specifically located in B genome and have relatively conservative characteristics based on the maps constructed by the John limes Centre and the pre-screening experiments conducted in this study. All the 61 specific sequences selected were used to analyze the genetic relationships between each of the five species in Sitopsis section and the wheat B genome. Greater genetic contribution to the B genome was found in Aegilops spelto ides compared with the other 4 Aegilops species, whereas several of which contribute differently and specifically to B chromosomes, when each chromosome of B genome analysized, that is, Aegilops longissima to 2B; Aegilops bicornis to 6B; Aegilops searssi to 6B; Aegilops speltoides to 7B and I B with the specific sequences.These results suggested that the B genome in the polyploid wheats could have a polyphyletic origin.
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