Abstract
The possibility of transferring sexually an incomplete chromosome complement between two uncrossable species was investigated. Pollen of Nicotiana tobacum were exposed to 137Cs gamma-rays (5-40kR) and were applied to stigmata of N.rustica. On the 6th or 7th day after the pollination, the ovules were detached from the placentae and were inoculated on solid medium. One hundred and fourteen mature hybrid plants were obtained through the ovule culture and they were classified into the following three groups on the basis of their morphological characteristics; (1) normal hybrids which were not distinguished from the hybrid plants obtained through crossing by unirradiated pollen, (2) anomalous hybrids which were cleglrly different from normal hybrids and (3) maternal hybrids which were not distinguished from the maternal parent. N.rustica and were fertile. More than 50 per cent of the obtained hybrid plants were the anomalous hybrids. The morphology of anomalous hybrids varied from that of haploid mother plants to that of normal hybrids and the chromosomes of these plants varied in number from 24 to 48. These results suggest that an incomplete chromosome complement of N.tabacum (n=24) is transferred into N.rustica (n=24) through the comblned techniques of crossing by irradiated pollen and in vitro culturing of crossed ovules.
