Submitted to: Plant Genetic Resources
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/31/2008
Publication Date: 7/1/2008
Citation: Tanaka, H., Morris, C.F., Haruna, M., Tsujimoto, H. 2008. Prevalence of puroindoline alleles in wheat varieties from eastern Asia including the discovery of a new SNP in puroindoline b. Plant Genetic Resources 6:142-152. Interpretive Summary: Grain hardness (‘kernel texture’) is one of the most important end-use quality characteristics of cultivated common wheat, as it has a profound effect on processing and utilization. Based on the texture of the mature wheat kernel, common wheat varieties are typically classified as “hard” or “soft”. Soft wheat varieties are used for cakes, cookies, pastries, and some types of noodles, whereas hard wheat varieties are used for breads and other yeast-leavened foods. In this study, the authors surveyed 246 varieties of common wheat from eastern Asia for kernel texture and puroindoline haplotype. The frequency of previously known puroindoline haplotypes in Asian common wheat is also described in this paper. The authors also report the discovery of a new SNP in puroindoline b. The wheat varieties studied were maintained at Tottori University as a part of the National Bioresources Project-Wheat, Japan. It was determined that the lowest frequency of hard varieties occurred in Korea and Southwestern Japan. Tibet and Pakistan also had low frequencies of hard varieties. The highest frequency of hard varieties appeared in Northeast China followed by Northwest China and Nepal.
Technical Abstract: Kernel texture (grain hardness) in common wheat, Triticum aestivum L., is of primary technological importance and is largely determined by puroindoline gene sequence and expression. We investigated the puroindoline haplotype of 246 Asian common wheat varieties. All but three were conclusively characterized for puroindoline a and b haplotype. Of the total, 174 possessed the soft Pina-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 HI of 56.1 to 97.8, nearly half (30) were Pina-D1a/Pinb-D1b, four were Pina-D1a/Pinb-D1c, 19 were Pina-D1a/Pinb-D1p, 10 were Pina-D1b/Pinb-D1a (‘a-null’), three were Pina-D1l/Pinb-D1a, two possessed a new C-to-T SNP mutation at position 382 which is tentatively designated Pinb-D1ab, one was a “double null” with neither puroindoline a nor b expression and no PCR-detectable gene sequence, and three had undetermined/ambiguous puroindoline a sequence but possessed Pinb-D1a. The double null was the hardest of all varieties tested with a HI of 97.8. The frequency of soft / hard and puroindoline hardness haplotype varied depending on the origin of the varieties. The lowest frequency of hard varieties occurred in Korea and Southwestern Japan. Tibet and Pakistan also had low frequencies of hard varieties. The highest frequency of hard varieties appeared in Northeast China followed by Northwest China and Nepal. Within Asia, the Pinb-D1p allele appears in a region extending from northeastern China through Inner Mongolia, northwestern China, Xinjiang and Tibet, with the greatest frequency in northwestern 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 three Pina-D1l varieties came from China. The newly-discovered SNP originated in Afghanistan and the ‘double null’ in Xinjiang.