ARS | Publication request: GROWTH HABIT, PLANT HEIGHT, AND FLOWERING QTLS IN NORTH AMERICAN LEYMUS WILDRYES

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 12, 2006
Publication Date: November 21, 2006
Citation: Larson, S.R., Wu, X., Jones, T.A., Jensen, K.B., Chatterton, N.J., Waldron, B.L., Robins, J.G., Bushman, B.S., Palazzo, A.J. 2006. Growth habit, plant height, and flowering qtls in north american leymus wildryes. Crop Science.

Interpretive Summary: Leymus cinereus and L. triticoides are tall caespitose and relatively short, rhizomatous perennial range grasses, respectively. High-density molecular genetic linkage maps were used to identify chromosome regions and map genes controlling circumference of plant rhizome spreading, proportion of reproductive bolting culms, anthesis date, and plant height in two full-sib families derived from two interspecific hybrids. Significant gene effects were detected and mapped in both families. Significant rhizome gene effects were associated with both copies of a duplicated chromosome region, in both Leymus wildrye families, which also correspond to branching mutations on barley chromosome 3H. The coincidence of gene effects related to lateral branching associated with this chromosome region suggest that it contains a fundamentally important gene that controls plant architecture in grasses. Likewise, major plant height gene effects were detected on Leymus chromosome LG2a, which may correspond with dwarfing mutations on barley 2H and wheat 2A. Overall patterns of genetic variation are consistent with directional selection for plant height and rhizome proliferation and balancing selection for flowering traits. Thus, we genetically mapped regions on Leymus chromosome LG2a and LG3a that contain functionally important genes controlling adaptive differences among divergent grasses and cereals. These genes are potentially important candidate for gene cloning efforts.

Technical Abstract: Leymus cinereus and L. triticoides are tall caespitose and relatively short, rhizomatous perennial grasses, respectively. High-density molecular genetic linkage maps were used for QTL analysis of circumference of plant spreading, proportion of bolting culms, anthesis date, and plant height in two full-sib mapping families (TTC1 and TTC2) derived from two L. triticoides x L. cinereus hybrids backcrossed to one L. triticoides tester. Two circumference QTLs, two bolting QTLs, and two height QTLs were detected in both families (homologous), but the remaining fourteen QTLs were unique to TTC1 or TTC2. Circumference QTLs were detected in homoeologous regions of LG3a and LG3b, in TTC1 and TTC2, which correspond to a preponderance of branching mutations on barley homoeologous group 3H. Major plant height QTLs were detected on TTC1 and TTC2 LG2a, which may correspond with gibberellin-insensitive (gai) mutations on barley 2H and wheat 2A. Divergent parental means, and synergistic QTL effects are consistent with directional selection for plant height and rhizome proliferation. Conversely, similar parental means, transgressive segregation, and antagonistic QTL effects may reflect balancing selection for flowering traits. Moreover, bolting deficiencies among interspecific progenies were strongly associated with early flowering. Differences between TTC1 and TTC2 QTL maps elucidate adaptive heterogeneity within natural source populations.