Submitted to: Journal of Theoretical and Applied Genetics
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/4/2004
Publication Date: 9/22/2004
Citation: Gedye, K.R., Morris, C.F., Bettge, A.D. 2004. Determination and evaluation of the sequence and textural effects of puroindoline a and puroindoline b genes in a population of synthetic hexaploid wheat. Theor. Appl. Genet. 109:1597-1603. Interpretive Summary: Variation in hardness is a primary end-use quality concern in wheat. Due to genetics and evolution, wheat's genetic variation for hardness is limited by one ancestor's genetic contribution to wheat. If relatives to this ancestral wheat could be used for breeding, additional softness genes might be obtained for wheat breeders to use in new crosses. This work shows that the use of "synthetic hexaploids" could provide access to these genetic resources. Synthetic hexaploids are constructed from durum wheat (a tetraploid) and the wild wheat ancestor Aegilops tauschii (a diploid) by CIMMYT, an international wheat research organization. Analysis of the puroindoline genes, which confer hardness or softness, in these synthetic hexaploid lines, revealed some new genetic variants that provide naturally-occurring softer endosperm texture. These softer wheat lines could be used in wheat breeding programs to produce softer wheat varieties.
Technical Abstract: Aegilops tauschii (2n=2x=14, DD) is a rich source of genetic variability for hexaploid wheat (Triticum aestivum, 2n=6x=42, AABBDD) improvement. This variability can be accessed through utilizing synthetic hexaploid wheat lines, which contain genomes from Ae. tauschii and Triticum turgidum (2n=4x=28, AABB). Numerous desirable characteristics can be and have been introgressed into common hexaploid wheat with this germ plasm. In this work, the genetic variability in the two puroindoline genes (a and b) contained on the D genome, and the relationship that sequence polymorphisms in these genes have on endosperm texture among a population of 75 CIMMYT synthetic hexaploid accessions is described. Kernel texture was evaluated using the Single Kernel Characterization System (SKCS). Kernel texture differed significantly (P 0.0001) among the synthetic hexaploid accessions (range 2.6 - 40.9) and the parent types, durum or Ae. tauschii. The interaction term between parent types was also a significant effect (P 0.0001). In addition to the 'wild- type' protein sequences of the puroindoline genes (those present in 'Chinese Spring' and all other soft wheats), three other translated sequences were identified in puroindoline a and two others in puroindoline b. These protein sequences were associated with significantly (P 0.001) softer endosperm textures than the wild-type protein sequences. As the softer alleles are expressed in a hexaploid background, they are immediately available to wheat breeding programs.