MOLECULAR CYTOGENETIC CHARACTERIZATION OF THINOPYRUM INTERMEDIUM-DERIVED WHEAT GERMPLASM SPECIFYING RESISTANCE TO WHEAT STREAK MOSAIC-VIRUS

Thinopyrum intermedium is a promising source of resistance to wheat st reak mosaic virus (WSMV), a devastating disease of wheat. Three wheat germplasm lines possessing resistance to WSMV, derived from Triticum a estivum x Th. intermedium crosses, are analyzed by C-banding and genom ic in situ hybridization (GISH) to determine the amount and location o f alien chromatin in the transfer lines. Line CI15092 was confirmed as a disomic substitution line in which wheat chromosome 4A was replaced by Th. intermedium chromosome 4Ai#2. The other two lines, CI17766 and A29-13-3, carry an identical Robertsonian translocation chromosome in which the complete short arm of chromosome 4Ai#2 was transferred to t he long arm of wheat chromosome 4A. Fluorescence in situ hybridization (FISH) using ABD genomic DNA from wheat as a probe and S genomic DNA from Pseudoroegneria stipifolia as the blocker, and vice versa, reveal ed that the entire short arm of the translocation was derived from the short arm of chromosome 4Ai#2 and the breakpoint was located at the c entromere. Chromosomal arm ratios (L/S) of 2.12 in CI17766 and 2.15 in A29-13-3 showed that the translocated chromosome is submetacentric. T his translocated chromosome is designated as T4AL.4Ai#2S as suggested by Friebe et al. (1991).