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Electrophoretic Evidence for Allotetraploidy with Segregating Heterozygosity in South African Pellaea rufa A. F. Tryon (Adiantaceae)
Gerald J. Gastony
Annals of the Missouri Botanical Garden
Vol. 77, No. 2 (1990), pp. 306-313
Published by: Missouri Botanical Garden Press
Stable URL: http://www.jstor.org/stable/2399545
Page Count: 8
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Pellaea rufa is a sexually reproducing tetraploid species with a chromosome number of n = 58 II at meiosis. Unlike previously reported tetraploid ferns, sporophytes of P. rufa exhibit substantial intrapopulational electrophoretic variation for respective enzyme phenotypes, and many of their heterozygous phenotypes are segregating rather than fixed. Two hundred and twenty individual gametophytes from a tetraploid sporophyte heterozygous for four alleles at the PGI-2 locus were subjected to electrophoresis to determine whether inheritance is tetrasomic as expected in an autotetraploid or disomic as expected in an allotetraploid. Results reject the hypothesis of autotetraploidy but fit expectations under the hypothesis that P. rufa is an allotetraploid with fixed intergenomic heterozygosity and segregating intragenomic heterozygosity. Observed intragenomic heterozygosity is consistent with a direct hybrid origin of allotetraploid P. rufa via gametes from unreduced spores and with a more probable indirect origin involving unreduced spores. from intermediate allodiploids. Disomic inheritance of intragenomic heterozygosity generates electrophoretic variation in P. rufa that is less than that in autopolyploids with polysomic inheritance but greater than that previously reported in allopolyploids.
Annals of the Missouri Botanical Garden © 1990 Missouri Botanical Garden Press