MOLECULAR CYTOGENETIC ANALYSIS OF AGROPYRON CHROMATIN SPECIFYING RESISTANCE TO BARLEY YELLOW DWARF VIRUS IN WHEAT

Nine families of bread wheat (TC5, TC6, TC7, TC8, TC9, TC10, TC14, 539 5-(243AA), and 5395) with resistance to barley yellow dwarf virus and containing putative translocations between wheat and a group 7 chromos ome of Agropyron intermedium (L1 disomic addition line, 7Ai#1 chromoso me) induced by homoeologous pairing or tissue culture were analyzed. C -banding, genomic in situ hybridization (GISH), and restriction fragme nt length polymorphism (RFLP) in combination with repetitive Agropyron -specific sequences and deletion mapping in wheat were used to determi ne the relative locations of the translocation breakpoints and the siz e of the transferred alien chromatin segments in hexaploid wheat-Agrop yron translocation lines. All homoeologous compensating lines had comp lete 7Ai#1 or translocated 7Ai#1-7D chromosomes that substitute for ch romosome 7D. Two complete 7Ai#1 (7D) substitution lines (5395-(243AA) and 5395), one T1BS-7Ai#1S . 7Ai#1L addition line (TC7), and two diffe rent translocation types, T7DS-7Ai#1S . 7Ai#1L (TC5, TC6, TC8, TC9, an d TC10) and T7DS . 7DL-7Ai#1L (TC14), substituting for chromosome 7D w ere identified. The substitution line 5395-(243AA) had a reciprocal T1 BS . 1BL-4BS/T1BL-4BS . 4BL translocation. TC14 has a 6G (6B) substitu tion. The RFLP data from deletion mapping studies in wheat using 37 gr oup 7 clones provided 10 molecular tagged chromosome regions for homoe ologous and syntenic group 7 wheat or Agropyron chromosomes. Together with GISH we identified three different sizes of the transferred Agrop yron chromosome segments with approximate breakpoints at fraction leng th (FL) 0.33 in the short arm of chromosome T7DS-7Ai#1S . 7Ai#1L (TC5, TC6, TC8, TC9, and TC10) and another at FL 0.37 of the nonhomoeologou s translocated chromosome T1BS-7Ai#1S . 7Ai#1L (TC7). One breakpoint w as identified in the long arm of chromosome T7DS . 7DL-7Ai#1L (TC14) a t FL 0.56. We detected some nonreciprocal translocations for the most proximal region of the chromosome arm of 7DL, which resulted in small duplications.