Genetics and Breeding of American Elm

From a genetic point of view, the predominate feature of American elm is polyploidy. All other species in the genus have a gametic chromosome number of 14 while American elm is a tetraploid with gametes containing 28 chromosomes. Polyploidy is not a common feature of the forest species on which most genetics and breeding research has been conducted although black cherry and yellow birch are among the important hardwood species which are polyploids. It may be well, therefore, to note the genetic consequences of tetraploidy. Tetraploids may be of three types: autotetraploids, allotetraploids, or a combination of both. Autotetraploids are characterized by multiples of one genome and multivalent chromosome association at meiosis. Allotetraploids arise from hybridization between diploid species and thus contain two pairs of different genomes with bivalent pairing at meiosis.

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Author(s): Donald T. Lester

Publication: Tree Improvement and Genetics - Northeastern Forest Tree Improvement Conference - 1968

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