Wheat–thinopyrum intermedium recombinants resistant to wheat streak mosaic virus and triticum mosaic virus
To date, only one gene conferring resistance to Wheat streak mosaic virus (WSMV) designated as Wsm1 was transferred from Thinopyrum intermedium (Host) Barkworth and Dewey to wheat (Triticum aestivum L.) in the form of a compensating Robertsonian translocation T4DL•4JsS. Wsm1 confers high levels of resistance to WSMV under field conditions; however, in certain genetic backgrounds and environments, the presence of the T4DL•4JsS translocation reduces agronomic performance. The objective of this study was to shorten the Th. intermedium segment in the T4DL•4JsS translocation. We recovered one proximal (rec36) and four distal (rec45, rec64, rec87, rec213) primary recombinants. Genomic in situ hybridization and molecular marker analyses determined the size of the Th. intermedium segments in the distal recombinants to be about 20% of the 4DS-4JsS arm. All primary recombinant stocks, together with appropriate controls, were evaluated for their resistance to WSMV and Triticum mosaic virus (TriMV) in greenhouse tests. Whereas the distal recombinants rec45, rec64, rec87, and rec213 were resistant to both WSMV and TriMV at low temperatures of 18°C, the proximal recombinant rec36 reacted susceptible, which mapped the Wsm1 gene to the distal 20% of the 4DS-4JsS arm. We successfully shortened the Th. intermedium segment while still retaining the Wsm1 gene. The T4DL•4DS-4JsS recombinant chromosome of the rec213 stock was transferred to adapted Kansas hard red winter wheat cultivars.