Reconciliation of D-genome puroindoline allele designations with current DNA sequence data

Kernel texture is an important trait in cereals, especially wheat (Triticum spp.). Throughout the Triticeae, the puroindoline genes act to soften kernel endosperm. Absence or mutation of either or both of the two puroindolines, ‘a’ and ‘b’, in Triticum aestivum results in harder grain texture. Apparently only one puroindoline haplotype was contributed by the Aegilops tauschii variety that contributed the D-genome during allopolyploidization. Yet, world collections of Ae. tauschii exhibit a range of puroindoline sequence polymorphisms. Consequently, these genes, through synthetic hexaploids (× Aegilotriticum) can enrich the wheat gene pool. Lastly, the puroindolines represent a useful tool for phylogenetic analyses. Here we review original sequence data published and/or available in public databases to reconcile the known gene sequence polymorphisms with a systematic approach to the designating of puroindoline gene and allele symbols in T. aestivum, Ae. tauschii, and × Aegilotriticum. This system follows the recommendations adopted by the International Wheat Genetics Symposium and described in the Catalogue of Gene Symbols for Wheat. Errors, discrepancies and ambiguities in the puroindolines are reviewed; a reconciliation of all existing data is outlined.