GRIFFITH, M. PATRICK. Rancho Santa Ana Botanic Garden, 1500 N. College Ave., Claremont, CA 91711; Department of Biology, Sul Ross State University, Alpine TX 79832. - Natural Interspecific Hybridization in Opuntia of the Northern Chihuahuan Desert Region.
Possible natural interspecific hybridization among taxa of
Opuntia subgenus Opuntia was investigated in the
northern Chihuahuan Desert region. The investigation employed
experimental hybridization and random amplified polymorphic DNA (RAPD)
data. Plants in the Sul Ross State University Garden representing
three ploidy levels, ten species, and three varieties were used for
all experiments. Reciprocal crosses were made between putative
parental taxa, and each cross was analyzed for fruit and seed set. For
each taxon, tests were performed to control for possible apomictic,
autogamous, and geitonogamous seed set. Data gathered from the tests
provided basic information regarding the breeding systems of the taxa
investigated. Reciprocal crosses between ploidy levels set fruit and
seed unidirectionally. Seed set data suggest that O.
engelmannii possibly spreads primarily through vegetative means,
or by dispersal of self-fertilized seed. RAPD banding pattern data
suggested that at least one Opuntia population was of hybrid
origin.
Key words: Chihuahuan Desert Region, hybridization, Opuntia