Null alleles for gliadin blocks in bread and durum wheat cultivars.

Wheat gliadin proteins are coded by clusters of genes (complex loci) located on the short arms of chromosomes of homoeologous groups 1 and 6 in bread (6x) and durum (4x) wheats. The proteins expressed by the various complex loci have been designated gliadin blocks. In a survey of accessions from the Germplasm Institute (C.N.R., Bari, Italy) collection, several different accessions have been found that lack particular blocks of proteins (null alleles). In some bread wheat accessions, seeds do not express gliadins that are coded by chromosomes 1D and 6A in normal cultivars. Similarly, some durum wheat accessions lack ω-gliadin components coded for by genes on chromosomes 1A and 1B. The missing proteins do not result from the absence of whole chromosomes, but may be the consequence of partial deletion of these genes at a complex locus or result from their silencing.