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Artificial and Natural Hybrids in the Gramineae, Tribe Hordeae. V. Diploid Hybrids of Agropyron

G. Ledyard Stebbins Jr. and Fung Ting Pun
American Journal of Botany
Vol. 40, No. 6 (Jun., 1953), pp. 444-449
Stable URL: http://www.jstor.org/stable/2438528
Page Count: 6
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Artificial and Natural Hybrids in the Gramineae, Tribe Hordeae. V. Diploid Hybrids of Agropyron
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Abstract

Agropyron spicatum and its var. inerme as well as A. caespitosum of southwestern Asia all are diploids with 7 pairs of chromosomes at meiosis and essentially normal meiotic behavior. The hybrid between A. spicatum and A. s. var. inerme likewise has nearly normal meiosis and is fertile. Hybrids between A. spicatum and A. s. var. inerme on the one hand and A. caespitosum on the other contain 7 pairs of chromosomes at meiosis in some of their sporocytes, but often have 2-4 univalents, which lag at later stages of meiosis. Bridge-fragment configurations are common at first and second anaphase. A genome consisting of chromosomes essentially homologous to those of A. spicatum and A. inerme appears to be widespread among diploid species and a component of many polyploid species of Agropyron and related genera. The cytogenetic evidence concerning relationships of these three species agrees with that from external morphology if all available characteristics and geographic distribution are considered, but not if emphasis is placed upon the characters most often used in taxonomic keys.

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