Hybridization of AA genome rice species from Asia and Australia .1. Crosses and development of hybrids

Interspecific and intraspecific crosses of rice species were made involving the AA genome wild species Oryza meridionalis Ng from Australia, O. nivara Sharma et Shastry, O. rufipogon Griff, the weedy type O. sativa f. spontanea Rosch., and the cultigen O. sativa L. from Asia. Seed set and the number of hybrids obtained from both interspecific and intraspecific crosses were low and no significant differences were observed between the interspecific and intraspecific crosses. In the combination O. meridionalis x O. nivara and O. meridionalis x O. rufipogon, considerable differences in reciprocal crosses were observed, whereas higher seed set and more hybrids were obtained when O. meridionalis was used as the female parent. Pollen stainability and seed fertility of hybrids were very low, averaging between 1% and 9% in both interspecific and intraspecific combinations, except in the O. nivara intraspecific cross of 105386 x 10611, whose hybrid showed 83.0% pollen stainability and 66.5% seed fertility.