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Title: SEQUENCE DIVERSITY OF PUROINDOLINE-A, PUROINDOLINE-B AND THE GRAIN SOFTNESS PROTEIN GENES IN AEGILOPS TAUSCHII COSS

Author
item MASSA, A - WASHINGTON STATE UNIV
item Morris, Craig
item GILL, B - WASHINGTON STATE UNIV

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/19/2003
Publication Date: 4/1/2004
Citation: Massa, A.N., Morris, C.F., Gill, B.S. 2004. Sequence diversity of puroindoline-a, puroindoline-b and the grain softness protein genes in Aegilops tauschii coss. Crop Sci. 44:1808-1816.

Interpretive Summary: A wild ancestor of wheat (Aegilops tauschii) constitutes a valuable resource of genetic variability for improving wheat. DNA sequence diversity of the “Hardness” locus was examined. The Hardness locus bears the puroindoline a and b genes, and the closely related Gsp-D1 gene. A distinct signature of polymorphism and selection was evident in each of the three genes across loci for 50 accessions of Ae. tauschii. Genetic variation at the puroindoline b locus was higher than expected. The sequence variation resolved here will help elucidate the kind of variation that may be important for the function of these genes, as well as to identify novel Ae. tauschii lines that may be used to broaden the range in wheat kernel softness. Lastly, these results may help in the development of new strategies for breeding purposes.

Technical Abstract: Aegilops tauschii Coss. constitutes a valuable resource of genetic variability for improving cultivated bread wheat Triticum aestivum L. Nucleotide sequence diversity was examined at the Hardness (Ha) locus, which bears the puroindoline-a (Pina-D1) and puroindoline-b (Pinb-D1) genes, and the closely related Gsp-D1 gene. A distinct signature of polymorphism and selection was evident in each of the three genes across loci for the 50 accessions of Ae. tauschii. Pinb-D1 was characterized by a high level of nucleotide diversity ('=0.02966; '=0.0166) relative to a low level of variation in the neighboring linked Pina-D1 and Gsp-D1 genes. Despite the close genetic and physical linkage among these three loci, recombination and linkage disequilibrium analyses detected at least two recombination events, most likely at the inter-locus level. Tests for neutrality showed that polymorphism at Pina-D1 and Gsp-D1 did not depart from a drift/mutation model. Genetic variation at the Pinb-D1 locus was higher than expected under neutrality suggesting that selection might operate to maintain polymorphism at this locus. The sequence variation resolved here will help elucidate the kind of variation that may be important for the function of these genes, as well as to identify novel Ae. tauschii genotypes that may be used to broaden the range in wheat endosperm texture. Lastly, these results on sequence diversity, linkage disequilibrium, and recombination may help in the development of new strategies for breeding purposes.