Puroindoline allele diversity in Canadian and northern US hard spring wheat varieties differing in kernel hardness

Abstract

Kernel hardness, one of the most important factors in determining the end-use suitability of wheat (Triticum aestivum L.), is largely influenced by puroindoline proteins a (PINA) and b (PINB). Soft texture is wildtype (Pina-D1a/Pinb-D1a) with hard texture being determined by either Pina-D1 gene deletion or point mutations in Pinb-D1a. The objectives of this study were to determine kernel hardness indices (HI) and Pina-D1/Pinb-D1 allelic diversity in a diverse set of 81 Canadian (representing eight wheat classes) and 49 US hard spring wheat varieties. Varieties were grouped into two experimental sets grown in replicated trials in 2004–2006 at Saskatoon, SK. Variation existed among varieties with HI means ranging from 21.7 (CDC Zorba) to 72.7 (AC Morse) in exp. 1 and from 25.0 (HY320) to 66.1 (Norlander) in exp. 2. Only AC Andrew, CDC Zorba, and Red Fife were soft kernel textured and carried the wildtype Pina-D1a/Pinb-D1a alleles. The majority of Canadian varieties were Pina-D1a/Pinb-D1b (69%), while a greater frequency of US varieties was Pina-D1b/Pinb-D1a (55%). Only four varieties, all from Quebec-based breeding programs, carried the Pinb-D1c allele. On average, varieties with the Pina-D1b allele had significantly harder kernels than those carrying the Pinb-D1b mutation. Durum wheat (T. turgidum L. var durum) varieties, included as hard-kernelled controls, possessed significantly harder kernels (average HI = 71.2) than spring wheat varieties with Pina-D1b (65.3). Varieties carrying Pina-D1b (null PINA) were harder than those carrying hardness mutations at the Pinb-D1 locus, but considerable overlap in hardness was evident among genotypic classes. This work represents the first extensive Pin genotyping combined with HI phenotyping survey of Canadian wheat varieties, which is expected to aid breeders in understanding how Pina-D1/Pinb-D1 allele composition is currently associated with kernel hardness across Canadian wheat classes. Key words: Triticum aestivum, kernel hardness, puroindolines