Microsatellite markers reveal chimeric origin of redesignated chromosome 4A of wheat from Triticum urartu and other species

Although a new nomenclature has been adopted for wheat in which chromosome 4A (4A(O)) has been renamed 4B (4B(N)) and chromosome 4B (4B(O)) has been r enamed 4A (4A(N)), their specific origin remains uncertain. The use of whea t microsatellite (WMS) markers mapped to chromosomes 4A(N) and 4B(N) in a s et of polyploid wheats and diploid genome donors has unequivocally indicate d that the entire short arm of 4A(N), some part of 4A(N)L, and a segment of 4B(N)L were derived from Triticum urartu. The presence of a T. urartu-spec ific allele at locus gwm368 on 4B(N)L and of an Aegilops speltoides allele at locus gwm397 on 4A(N)L suggests the possibility of a reciprocal transloc ation between 4A(N)L and 4B(N)L. The subcentromeric and telomeric regions o f 4A(N)L corresponding to heterochromatic C-bands were derived neither from diploid wheats nor from Ae. speltoides or Aegilops longissima.