Interspecific Hybridization in the Genus Dioscorea

Interspecific hybridization between Dioscorea alata (2n = 60).D. deltoidea (2n = 20), D. floribunda (2n = 36), D. composita(2n = 36), and D. friedrichsthallii (2n = 36) has revealed levelsof crossability consisting of successful crossing and normalgermination of hybrid seeds, successful crossing but poor germinationof hybrid seeds, crosses not successful due to a pre-fertilizationovular breakdown, and crosses not successful due to post-fertilizationovular breakdown. In general the three Central American species with basic chromosomenumber as 9, namely D. floribunda, D. composita, and D. friedrichsthalliiare cross compatible. In crosses involving D. floribunda withD. composita and D. floribunda with D. friedrichsthallii viablehybrids were obtained. The cross between D. friedrichsthalliiand D. composita is also successful but germination of the hybridseeds is greatly reduced. The cross of D. composita female withthe male D. friedrichsthallii was an exception to the generalcompatibility between these three species. In this cross thefertilized embryo aborted after attaining four-celled stage. The crosses between the two Old World species with basic chromosomenumber as 10, namely D. alata and D. deltoidea with each otherand with the above named three Central American species werenot successful. D. alata had pollen grains which rarely germinated.When D. alata was used as the female parent, the pollen tubesof other species grew down the style but no fertilization tookplace. The reciprocal crosses of D. deltoidea with the CentralAmerican species gave differential results. When D. deltoideawas used as the female parent no fertilization took place. However,when D. deltoidea was used as the male parent the fertilizedembryo aborted after attaining globular stage.