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Title: The distal portion of wheat (Triticum aestivum L.) chromosome 5D short arm controls endosperm vitreosity and grain hardness

item Morris, Craig
item Beecher, Brian

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/13/2012
Publication Date: 6/15/2012
Citation: Morris, C.F., Beecher, B.S. 2012. The distal portion of wheat (Triticum aestivum L.) chromosome 5D short arm controls endosperm vitreosity and grain hardness. Theoretical and Applied Genetics. 125:247-254.

Interpretive Summary: Endosperm texture is a leading trait influencing the quality and utilization of wheat grain. The major classes of endosperm texture: soft, hard and durum, can be explained by the presence, absence or gene sequence of puroindoline a and b, which reside at the Hardness locus on the short arm of chromosome 5D. In the present report, we found the expected association between kernel texture, that is 'soft' and 'durum hard' and the presence / absence of the distal portion of 5D. In this regard, the "removal" of the puroindolines/Hardness locus via the Chinese Spring deletion stock of Endo and Gill (1996) is, in a way, the reverse of the introduction of the puroindolines/Hardness locus into durum. The present work reflects a convergence of several factors: the development of deletion stocks in wheat, the creation of advanced back-cross derived near isogenic lines, the efficient "phenotyping" performed by the SKCS, and an appreciation for and knowledge of wheat grain texture and genetics.

Technical Abstract: Kernel vitreosity is an important trait of wheat grain, but its complete developmental control is not known. We developed back-cross seven (BC7) near isogenic lines in the soft white spring wheat cultivar Alpowa that possess or lack the distal portion of chromosome 5D short arm. This deletion was derived from Chinese Spring 5DS del-2 line of Endo and Gill (1996) (Gill et al. 1996). From the final back-cross, 46 BC7F2 plants were isolated. These plants exhibited a complete and perfect association between kernel vitreosity (i.e. vitreous, non-vitreous or mixed) and Single Kernel Characterization System (SKCS) hardness. Observed segregation of 10:28:7 fit a 1:2:1 Chi-square. BC7F2 plants classified as heterozygous for both SKCS hardness and kernel vitreosity (n = 29) were selected and a single vitreous and non-vitreous kernel were selected, and grown to maturity and subjected to SKCS analysis. The resultant phenotypic ratios were, from non-vitreous kernels, 23:6:0, and from vitreous kernels, 0:1:28, soft:heterozygous:hard, respectively. Three of these BC7F2 heterozygous plants were selected and 40 kernels each drawn at random, grown to maturity and subjected SKCS analysis. Phenotypic segregation ratios were 7:27:6, 11:20:9, and 3:28:9, soft:heterozygous:hard. Chi-square analysis supported a 1:2:1 segregation for one plant but not the other two, in which cases the two homozygous classes were under-represented. Twenty-two paired BC7F2:F3 full sibs were compared for other kernel traits. SKCS hardness differed markedly, 29.4 for the lines with a complete 5DS, and 88.6 for the lines possessing the deletion. The soft non-vitreous kernels were on average significantly heavier, by nearly 20%, and were slightly larger. Density and protein contents were similar, however.