Precise identification of wheat - Thinopyrum intermedium translocation chromosomes carrying resistance to wheat stripe rust in line Z4 and its derived progenies.

The wheat - Thinopyrum intermedium derived line Z4 has displayed novel and effective stripe rust resistance for over 40 years. This study aimed to precisely identify the chromosome constitution of line Z4 and determine the stripe rust resistance contribution using multicolor fluorescent in situ hybridization (FISH) and molecular marker analysis. The results indicated that the Z4 line (2n = 44) contained two pairs of non-Robertsonian translocations without the 3A chromosomes of wheat. FISH karyotypes of F3 progenies derived from crosses between Z4 and MY11 indicated that the transmission of the translocated chromosomes appeared normal and the number of wheat chromosomes 3A and 3D frequently varied. The FISH signal distribution of a new repetitive probe, named Oligo-3A1, confirmed the physical breakage points on chromosome 3AL incorporated into translocated chromosomes. PLUG markers revealed the breakage points on chromosomes 3A, 7JS, and 3D invloved in the translocated chromosomes, and they were designated as T3DS-3AS.3AL-7JSS and T3AL-7JSS.7JSL. Stripe rust resistances surveys indicated that the proximal region of 7JSS or 7JSL may confer the resistance at the adult plant stage. The precise characterization of the chromosome complements of wheat - Th. intermedium Z4 and derived progenies has demonstrated the importance of combining cytogenetic and molecular approaches in the genomics era for further wheat genetic manipulation and breeding purposes.