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 progenitor 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 intergenomic translocation types were observed and their breakpoints analyzed by genomic in situ hybridization. The previously reported species-specific 6A(t)-1G-4G cyclic translocation was found in all accessions studied. In four translocation types, the breakpoints were in interstitial regions of chromosomes and the other four arose via centric-breakage-fusion. A model is presented on the mechanism of origin and the adaptive significance of translocations with centromeric and noncentromeric breakpoints.