Taxonomic status of Oryza glumaepatula Steud. II. Hybridization between New World diploids and AA genome species from Asia and Australia

Intraspecific and interspecific crosses were made using O. glumaepatula Steud., O. rufipogon Griff., O. nivara Sharma et Shastry, O. meridionalis Ng, and other diploid accessions from the New World to determine biosystematic relationships among the New World, Asian, and Australian AA genome species. All intraspecific and interspecific combinations produced seeds and hybrids, but at different levels of success. The O. glumaepatula, O. rufipogon, and O. nivara intraspecific hybrids were generally fertile with mean pollen stainability ranging from 75.2% to 80.1% and mean spikelet fertility varying from 32.1% to 87.7%. The O. meridionalis intraspecific crosses showed 3.8% pollen stainability and 0.1% spikelet fertility. Interspecific hybrids showed varying fertilities. Crosses of O. glumaepatula with the New World diploid accessions IRGC 103812 and 105561 produced highly fertile hybrids with 68.0% to 89.7% pollen stainability and 70.8% to 86.6% spikelet fertility. In crosses between O. glumaepatula and the Asian species and other diploid New World accessions IRGC 100961, 103810, and 104386, sterile hybrids were produced with pollen fertility ranging from 0 to 35.1% and spikelet fertility from 0 to 8.2%. IRGC 103810 and 104386 formed fertile hybrids when crossed to O. nivara and O. rufipogon, which were also interfertile. Interspecific crosses of O. meridionalis with the other species produced highly sterile hybrids.