Submitted to: The Nucleus
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 20, 2011
Publication Date: August 1, 2012
Citation: Jauhar, P.P., Peterson, T.S. 2012. Synthesis and cytological analyses of hybrids between hexaploid wheat, with and without Ph1, and diploid wheatgrass. The Nucleus. 54:57-63. Interpretive Summary: Wide hybridization of wheat with related wild species can be very useful for incorporating desirable alien traits. Diploid wheatgrass with only two sets of chromosomes (chromosomes are rod-like structures that control various traits) is a source of several desirable traits including scab resistance. Pairing of chromosomes of parental species in their hybrids is essential for transferring desirable genes from one species to another. Such a chromosome pairing is called homoeologous pairing, i.e., pairing among similar, but not identical, chromosomes. This study reports on the synthesis and chromosomal study of hybrids of wheat with wheatgrass and highlights homoeologous pairing in some hybrids. The major regulatory gene called Ph1 does not allow pairing among chromosomes of different species. Therefore, we hybridized wheatgrass with a wheat variety without this gene and were able to induce pairing among the wheat and grass chromosomes. Varying degrees of homoeologous pairing in the intergeneric hybrids could facilitate gene transfer from the grass parent into wheat.
Technical Abstract: The usefulness of wide hybridization in genetic enhancement of crop plants is well documented. Diploid wheatgrass is a source of several desirable traits including Fusarium head blight resistance. The objective of this study was to report on the synthesis and cytological analyses of wheat × wheatgrass hybrids and highlight the homoeologous pairing. We hybridized wheatgrass with two important, crossable cultivars, ‘Chinese Spring,’ and ‘Fukohokomuji,’ of bread wheat, Triticum aestivum L. (2n = 6x = 42; AABBDD) and produced 11 tetraploid (2n = 4x = 28; ABDE) and two pentaploid (2n = 5x = 28; ABDEE) hybrids. To help promote homoeologous pairing and hence genetic recombination between the wheat and grass chromosomes, we used the Chinese Spring mutant ph1bph1b. We employed an easy and rapid means of detecting intergeneric hybrids without Ph1. The pentaploid hybrids resulted from the fusion of a normal 21-chromsome gamete of the wheat parent with an unreduced 14-chromsome gamete of diploid wheatgrass and showed a remarkable degree of Ph1-enforced preferential pairing among the homologous chromosomes resulting from a functioning unreduced gamete of the L. elongatum parent. The hybrids without Ph1 showed multivalent formation involving wheat and grass chromosomes. Varying degrees of homoeologous pairing detected could facilitate alien gene transfer into wheat.