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The Hybridization Barrier between Herbaceous Medicago sativa and Woody M. arborea Is Weakened by Selection of Seed Parents
Agronomy Department, University of Wisconsin, Madison, WI 53706, USA
School of Agriculture and Food Science, University of Queensland, Brisbane, Qld 4072, Australia
* Author to whom correspondence should be addressed.
Received: 14 April 2013; in revised form: 12 May 2013 / Accepted: 23 May 2013 / Published: 31 May 2013
Abstract: Medicago sativa, alfalfa or lucerne, and M. arborea were considered reproductively isolated until recently. Then, in 2003, an alfalfa genotype was identified that produced a few seeds and progeny with hybrid traits after a large number of pollinations by M. arborea. A derivative of this alfalfa genotype also produced a low frequency of progeny with hybrid traits. Thus, the hybridization barrier was weakened by selection of seed parents. Hybrids from both events expressed traits from M. arborea and M. arborea-specific DNA bands, although more of the M. sativa genome was retained, based on the DNA results. Thus, there was chromatin elimination during embryogenesis, resulting in partial hybrids (hereafter hybrids). However, more than 30 hybrids with an array of M. arborea traits have been obtained thus far, and research continues on the nature of the hybrids. Traits have been genetically transmitted in crosses, and selected traits are in use for alfalfa breeding. This paper reviews the first hybrids and then focuses on further weakening of the hybridization barrier with the discovery of a more efficient hybridizer derived from crossing Medicago sativa subspecies, sativa, coerulea and falcata. This genotype was found to have reproductive abnormalities associated with its complex subspecies origin that are best described as hybrid breakdown. In effect, this subspecies derivative is a bridge-cross parent that consistently produces hybrids. Reproductive abnormalities in the bridge-cross parent are reported and discussed.
Keywords: species; subspecies; interspecific hybrids; genetics; genome; genome shock; hybrid breakdown; plant breeding
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MDPI and ACS Style
Bingham, E.; Armour, D.; Irwin, J. The Hybridization Barrier between Herbaceous Medicago sativa and Woody M. arborea Is Weakened by Selection of Seed Parents. Plants 2013, 2, 343-353.
Bingham E, Armour D, Irwin J. The Hybridization Barrier between Herbaceous Medicago sativa and Woody M. arborea Is Weakened by Selection of Seed Parents. Plants. 2013; 2(2):343-353.
Bingham, Edwin; Armour, David; Irwin, John. 2013. "The Hybridization Barrier between Herbaceous Medicago sativa and Woody M. arborea Is Weakened by Selection of Seed Parents." Plants 2, no. 2: 343-353.