A Bayesian approach for discriminating among alternative inheritance hypotheses in plant polyploids: the allotetraploid origin of genus Borderea (Discoreaceae).

Catalán, P., Segarra-Moragues, J.G.; Palop-Esteban, M.; Moreno, C; González-Candelas, F.. A Bayesian approach for discriminating among alternative inheritance hypotheses in plant polyploids: the allotetraploid origin of genus Borderea (Discoreaceae).. Genetics. 2006, Vol. 172(3), p. 1939-2006.

Polyploidy is a common phenomenon occurring in a vast number of land plants. Investigations of patterns
of inheritance and the origins of plants (i.e., autopolyploidy vs. allopolyploidy) usually involve
cytogenetic and molecular studies of chromosome pairing, chromosome mapping, and marker segregation
analysis through experimental crosses and progeny tests. Such studies are missing for most wild species, for
which artificial crosses are difficult, not feasible, or unaffordable. We report here a Bayesian method to
discriminate between alternative inheritance patterns in the two extant, tetraploid species of the monocot
genus Borderea (Dioscoreaceae), which does not involve progeny array tests. Our approach is based on the
screening of a large number of SSR genotypes, which were obtained from successful amplifications of 17
microsatellite regions in individuals of both B. chouardii and B. pyrenaica.We tested for tetrasomic vs. disomic
modes of inheritance, using the Bayes factor test. Assignment of genotypes under both alternatives could be
unequivocally done for 14 and 11 of the 17 studied microsatellite regions in B. chouardii and B. pyrenaica,
respectively, totaling 9502 analyzed genotypes. The comparison of posterior probabilities for the two
competing hypotheses across the surveyed loci clearly favored a disomic inheritance pattern. Linkage tests
indicated that none of the studied SSR loci were in linkage disequilibrium, thus representing independent
samples of the Borderea genome. These results, along with previous allozyme data, support the allotetraploid
origin of this paleoendemic genus and reveal the lowest reported chromosome base number
for the family of the yams.