ABSTRACT
Twenty-five partial amphiploids (2n=8x=56), which were derived from hybrids of wheat (Triticum aestivum L.) with either Thinopyrum ponticum (Podpera) Liu & Wang, Th. intermedium (Host) Barkworth & D. Dewey, or Th. junceum (L.) A. Löve, were assayed for resistance to BYDV serotype PAV by slot-blot hybridization with viral cDNA of a partial coat protein gene. Three immune lines were found among seven partial amphiploids involving Th. ponticum. Seven highly resistant lines were found in ten partial amphiploids involving Th. intermedium. None of eight partial amphiploids or 13 addition lines of Chinese Spring - Th. junceum were resistant to BYDV. Genomic in situ hybridization demonstrated that all of the resistant partial amphiploids, except TAF46, carried an alien genome most closely related to St, whether it was derived from Th. ponticum or Th. intermedium. The two partial amphiploids carrying an intact E genome of Th. ponticum are very susceptible to BYDV-PAV. In TAF46, which contains three pairs of St- and four pairs of E-genome chromo somes, the gene for BYDV resistance has been located to a modified 7 St chromosome in the addition line L1. This indicates that BYDV resistance in perennial polyploid parents, i.e., Th. ponticum and Th. intermedium, of these partial amphiploids is probably controlled by a gene(s) located on the St-genome chromosome(s).
