Zymogram patterns of α-amylase isozymes inEthiopian tetraploid wheat landraces: insight into their evolutionaryhistory and evidence for gene flow

Abstract

The variation for α-amylaseisozymes was analyzed in 71 tetraploid wheat (AABB genome)landraces from Ethiopia, including accessions of Triticumdicoccon Shrank, T.turgidum L., T.durum Desf., T.pyramidale Percival and T.aethiopicum Jakubz., by thin-layerpolyacrylamide gel isoelectric focusing. Four zymogram phenotypeswere obtained from all the materials studied. Except inT. dicoccon, however, thestandard pattern of the durum wheat variety, LD222, was predominant.T. dicoccon showed twozymogram types that differed for the absence or consistently weakactivity of band 18(α-Amy-B1)of the malt type. Band 1(α-Amy-B3)of the malt type was fixed in T.dicoccon and present in only 10% of thefree-threshing (FT) types. Generally, the resultsindicated that the variation forα-amylase isozymes in cultivatedtetraploid wheats, including landraces from secondary centers, is lowpossibly due to the founder effect or as a result of selection. Thedata were useful for inferences about the evolutionary history ofEthiopian wheat landraces. It is speculated thatT. dicoccon was the firstwheat to arrive in the Ethiopian highlands ca.5000 years ago. However, it is not known whether the present day FTEthiopian tetraploid wheat landraces are direct descendants ofT. dicoccon, or whetherthey were introduced independently. The clear differences inα-amylase zymogram patterns favor the latterhypothesis. However, the presence of band1 in some of the FT types indicated the occurrence of geneflow between the FT types and T.dicoccon, which may also explain thequantitative nature of spike threshability in these landraces.Possible implications for durum wheat breeding arediscussed.