DETECTION OF INTERGENOMIC TRANSLOCATIONS WITH CENTROMERIC AND NONCENTROMERIC BREAKPOINTS IN TRITICUM-ARARATICUM - MECHANISM OF ORIGIN AND ADAPTIVE SIGNIFICANCE

Triticum araraticum Jakubz. (2n = 4x = 28, A(t)A(t)GG), a wild progeni tor of the polyploid cultivated wheat T. timopheevii, shows extensive chromosome translocation polymorphism in natural populations from the Middle East and Transcaucasia. From an extensive survey, eight interge nomic translocation types were observed and their breakpoints analyzed by genomic in situ hybridization. The previously reported species-spe cific 6A(t)-1G-4G cyclic translocation was found in all accessions stu died. In four translocation types, the breakpoints were in interstitia l regions of chromosomes and the other four arose via centric-breakage -fusion. A model is presented on the mechanism of origin and the adapt ive significance of translocations with centromeric and noncentromeric breakpoints.