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A System for Genetic Change in Apomictic Eastern Gamagrass

USDA-ARS, Southern Plains Range Res. Stn., 2000 18th St., Woodward, OK 73801

^* Corresponding author (a031cwwodwar{at}attmail.com).

The ability of a species to undergo genetic change is a necessary component of its adaptive evolution, which can lead to the widening or narrowing of its genetic base. In diplosporous apomictic species, change through sexual or meiotic means is limited or omitted entirely. The objective of this study was to investigate the reproductive attributes of tetraploid apomictic eastern gamagrass, Tripsacum dactyloides var. dactyloides (L.) L. One-hundred progeny generated from an apomictic tetraploid eastern gamagrass accession were evaluated at a phenotypic, cytogenetic, and molecular level by means of random amplified polymorphic DNA (RAPD) procedures to detect their genetic relatedness to the maternal parent and to each other. Differences in phenotype and RAPD-PCR (polymerase chain reaction) banding profiles, followed by chromosome counts, revealed the generation of new tetraploid variants. The identification of genetic variation in tetraploid progeny would presumably indicate the production of hybrid individuals generated from the fertilization of a reduced egg cell by a sperm nuclei. However, this study indicates the complete omission of hybrid individuals generated from expected normal sexual behaviors and suggests the observed variation is generated by an incomplete or dysfunctional sexual process. The incidence of this behavior was 4%. The detection and generation of genetically variable but cytologically stable tetraploids, from an apomictic eastern gamagrass, suggests the presence of an additional mechanism whereby this species routinely may undergo genetic change without the introduction of new germplasm.

Received for publication December 15, 1994.

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