Genetic variation for waxy proteins and starch properties in Italian wheat germplasm

Granule-bound starch synthase (GBSS) is the primary enzyme responsible for the synthesis of amylose in amyloplasts of cereal endosperm cells. In bread wheat there are three structural genes (Wx-A1, Wx-B1, and Wx-D1) encoding for isoforms of GBSS. The loss of one or more GBSS isoforms results in the reduction (partial- waxy) or absence (waxy) of amylose in the starch. Waxy wheats may find application in the production of modified food starch and their flour may be used to extend the shelf life of baked products. In order to breed high quality wheats able to produce bread with delayed staling, the genetic variability for the waxy trait in our germplasm has been investigated. We analysed 288 cultivars of bread wheat, 139 cultivars of durum wheat and about 200 accessions from other Triticum species. Gel electrophoresis showed 63 bread wheats deficient in the Wx-B1, one in the Wx-A1 and one in the Wx-D1 protein isoforms, as well as one Triticum dicoccum lacking the Wx-A1 isoform. None of the analysed Triticum monococcum, Triticum durum, Triticum spelta and Triticum timopheevi accessions showed mutations at the Wx loci. The wheat accessions with Wx mutations were evaluated with a Rapid Visco Analyser (RVA) to investigate starch properties. All the analysed cultivars showed Peak Viscosity and Final Viscosity different from the normal wheat. Other analyses to evaluate the rheological characteristics of the partial-waxy genotypes are under way and a breeding programme to select new waxy wheat varieties is in progress.