ARS | Publication request: Prevalence of puroindoline b-2 variants in U.S. Pacific Northwest wheat breeding germplasm pools, and their association with kernel texture

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 28, 2011
Publication Date: January 10, 2012
Repository URL: http://naldc.nal.usda.gov.d2.nal.usda.gov/download/54538/PDF
Citation: Geng, H., Beecher, B.S., He, Z., Kiszonas, A., Morris, C.F. 2012. Prevalence of puroindoline b-2 variants in U.S. Pacific Northwest wheat breeding germplasm pools, and their association with kernel texture. Theoretical and Applied Genetics. 124:1259-1267.

Interpretive Summary: Kernel texture is an important end-use quality trait in wheat. Amongst the primary wheats of commerce, three kernel texture classes are recognized: soft and hard hexaploid (T. aestivum), and very hard durum (T. turgidum ssp. durum). The genetic basis for these classes is well established and can be explained by the presence, absence or gene sequence of the puroindolines, ‘a’ and ‘b’ (Pina, Pinb), coded at the Pina-D1 and Pinb-D1 loci on the distal end of the short arm of chromosome 5D. The present review is restricted to kernel texture phenotypes measured by the SKCS. The present report re-examines the possible role of the Puroindoline b-2 gene in wheat kernel texture in a regional wheat gene pool largely unrelated to previous studies on Pinb-2. Released cultivars and advanced lines were drawn from seven years of testing and include soft winter, soft spring, hard winter and hard spring types. Additionally, soft white club, and red and white hard grained varieties were included. All germplasm were haplotyped for Pina-D1 and Pinb-D1, and for the Pinb-2 variants 2 and 3. Phenotypic SKCS kernel texture data were obtained from 3-7 locations per year. The study is divided into two parts, the first deals with haplotype frequency amongst varieties, the second deals with the multi-environment SKCS phenotypic data.

Technical Abstract: Kernel texture is a major factor influencing the classification and end use properties of bread wheat (Triticum aestivum L.), and is mainly controlled by the genes puroindoline a (Pina) and puroindoline b (Pinb). Puroindoline b2 was a new puroindoline-like gene identified. In this study, 400 wheat cultivars and advanced lines from the U.S. Pacific Northwest were investigated for frequencies of Puroindoline alleles and Puroindoline b2 variants. Results indicated that Pinb-D1b (74.1%) was the predominant genotype compared with Pina-D1b (25.9%) in 102 hard wheats, only 7 of 102 hard winter varieties carried Pinb-D1b. Pinb-2v3 (85%) was the predominant genotype compared with Pinb-2v2 (15%). Among 250 winter wheat varieties included 133 soft white winter, 33 hard white winter, 69 hard red winter and 15 soft white club wheat varieties, all (100%) carried Pinb-2v3. Using 255 of the 400 wheat varieties, we further analyzed the relationship between Puroindoline alleles and Puroindoline b2 variants and kernel texture. Results indicated kernel texture was significantly negatively correlated with both kernel weight and kernel diameter. Among seven crop years, coefficients of variation (CV %) of kernel texture for the soft spring wheat group varied from 9.5 to 14.7, for soft winter wheat 6.9 to 14.3, for hard spring wheat 3.3 to 5.2, and for hard winter wheat 3.0 to 7.1. For all four wheat groups, the broad-sense heritability (h2) of kernel texture was rather low and wider variation among most of the seven crop years. For both of Puroindoline b2 variant alleles (Pinb-2v2 and Pinb-2v3) the average kernel texture of varieties with Pina-D1b/Pinb-D1a was significantly higher than those of varieties with Pina-D1a/Pinb-D1b, whereas no significant difference between the Pinb-2v2 and Pinb-2v3 groups was obtained among subgroup of varieties with either the Pina-D1a/Pinb-D1b or Pina-D1b/Pinb-D1a allele. The study of Puroindoline b2 variants in U.S. Pacific Northwest wheat germplasm could provide useful information for improving processing quality and further understanding the molecular and genetic basis of kernel texture in bread wheat.