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The Genus Collinsia. XX. Cytogenetic Studies of Interspecific Hybrids

E. D. Garber and T. S. Dhillon
Botanical Gazette
Vol. 123, No. 4 (Jun., 1962), pp. 291-298
Stable URL: http://www.jstor.org/stable/2473177
Page Count: 8
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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.
The Genus Collinsia. XX. Cytogenetic Studies of Interspecific Hybrids
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Abstract

1. Thirty interspecific hybridizations involving thirteen species of Collinsia Nutt. (Scrophulariaceae) were attempted; eighteen yielded seed that germinated. 2. Seed from crosses between C. bruceae and either C. bartsiaefolia or C. austromontana yielded dwarf seedlings which died before flowering; seed from the cross between C. bruceae and C. concolor gave many dwarf seedlings which died before flowering, though some survived. 3. Except for a triploid hybrid from the cross between C. austromontana and C. solitaria and for a trisomic hybrid from the cross between C. heterophylla and "C. bartsiaefolia" and from the cross between C. austromontana and "C. bartsiaefolia," the interspecific hybrids were diploid. 4. Hybrids within the group including C. concolor and the two collections assigned to C. bartsiaefolia and the hybrid between C. corymbosa and "C. bartsiaefolia" were fertile; the remaining hybrids did not set seed when self-pollinated. Several hybrids had aborted anthers which precluded self-pollination. 5. Hybrids between species in Group I and between C. corymbosa and "C. bartsiaefolia" exhibited bivalents or bivalents and univalents; the remaining interspecific hybrids displayed either one or two interchange complexes with four, six, eight, or twelve chromosomes at metaphase I. 6. Hybrids between species in Group I, between "C. bartsiaefolia" and either C. multicolor or C. corymbosa, and between C. bartsiaefolia and C. multicolor did not have a dicentric chromatid bridge and fragment at anaphase I; the remaining hybrids displayed one or two dicentric chromatid bridges and fragments at this stage. 7. Many interspecific hybrids combined floral characters found in the parental species. 8. The significance of the chromosome formulas for the various species devised to account for the number both of interchange complexes and of chromosomes in each complex in recognizing species in Collinsia is discussed.

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