Genomic origins of Thinopyrum chromosomes specifying resistance to wheat streak mosaic virus and its vector, Aceria tosichella

The genomic origin of alien chromosomes carrying resistance to wheat streak mosaic virus (WSMV) and the wheat curl mite (WCM), Aceria tosichella Keife r, was evaluated in nine wheat-alien addition, substitution, or translocati on lines, derived from hybrids of wheat with Thinopyrum ponticum (Podp.) Ba rkworth & D.R. Dewey (2n = 10x = 70), or with Th. intermedium (Host) Barkwo rth & D.R. Dewey (2n = 6x = 42). One of the four wheat x Th. ponticum lines was resistant to WSMV and WCM. The other three lines were resistant to WCM , but susceptible to WSMV. Five wheat x Th. intermedium lines were suscepti ble to WCM, but were highly resistant to WSMV. Genomic in situ hybridizatio n (GISH) using different genomic DNA probes demonstrated that all WSMV- and WCM-resistant lines carried an alien chromosome(s) related to the J(s) gen ome in Th. ponticum and Th. intermedium. The J(s) alien chromosome(s) displ ayed a special GISH hybridization pattern with the S genomic DNA probe, in which S genome DNA hybridized strongly in the centromeric regions and occas ionally in the terminal regions with no or a weak hybridization signal in t he middle of the two arms of the chromosomes. The WCM-resistant wheat x Th. ponticum lines N/5.10.10 and 63-30-2-2-2-8-1 carried the same short arm of chromosome 6J(s) derived from the partial amphiploid Agrotana, while the W SMV-resistant wheat x Th. intermedium lines T-Ai, CI15092, CI17766, A29-13- 3-1 and KS93WGRC27 all had the same alien chromosome or chromosome arm of 4 J(s) from Th. intermedium. The J(s) genome present in Th. ponticum and Th. intermedium is an important source of WSMV and WCM resistance that can be t ransferred into wheat.