Prevalence of puroindoline alleles in wheat varieties from eastern Asia including the discovery of a new SNP in puroindoline b

Abstract

Kernel texture (grain hardness) in common wheat (Triticum aestivumL.) is of primary technological importance and is largely determined by puroindoline gene sequence and expression. We investigated the puroindoline haplotypes of 246 Asian common wheat varieties. All but three were conclusively characterized for puroindoline a and b haplotypes. Of the total, 174 possessed the softPina-D1a/Pinb-D1a‘wild-type’ gene sequences with SKCS hardness indexes (HI) ranging from 13.5 to 61.8. Among the remaining 72 varieties with HIs of 56.1–97.8, nearly half (30) werePina-D1a/Pinb-D1b, 4 werePina-D1a/Pinb-D1c, 19 werePina-D1a/Pinb-D1p, 10 werePina-D1b/Pinb-D1a(‘a-null’), 3 werePina-D1l/Pinb-D1a, 2 possessed a new C-to-T SNP mutation at position 382, which is tentatively designatedPinb-D1ab, 1 was a ‘double null’ with neither puroindoline a nor b expressed and no PCR-detectable gene sequence, and 3 had undetermined/ambiguous puroindoline a sequence but possessedPinb-D1a. The double null was the hardest of all varieties tested with an HI of 97.8. The frequency of soft and hard varieties and puroindoline hardness haplotype varied depending on the origin of the varieties. The lowest frequency of hard varieties occurred in Korea and south-western Japan. Tibet and Pakistan also had low frequencies of hard varieties. The highest frequency of hard varieties appeared in north-east China followed by north-west China and Nepal. Within Asia, thePinb-D1pallele appears in a region extending from north-eastern China through Inner Mongolia, north-western China, Xinjiang and Tibet, with the greatest frequency in north-western China. This allele was also present in Pakistan and Afghanistan, but not found in Japan, and may have been dispersed along the ‘Silk Road’. All threePina-D1lvarieties came from China. The newly discovered SNP originated in Afghanistan and the ‘double null’ in Xinjiang.