ALLOTETRAPLOID HYBRIDS BETWEEN CITRUS AND 7 RELATED GENERA PRODUCED BY SOMATIC HYBRIDIZATION

We have developed an efficient protoplast-fusion method to produce som atic hybrid allopolyploid plants that combine Citrus with seven relate d genera, including four that are sexually incompatible. In this paper we report the creation of 18 new allotetraploid hybrids of Cirrus, in cluding ten among sexually incompatible related genera, that may have direct cultivar potential as improved citrus rootstocks. All hybrids w ere confirmed by cytological and RAPD analyses. If fertile, the attrib utes of these hybrids may be amenable to further genetic manipulation by breeding at the tetraploid level. Wide somatic hybridization of Cit rus via protoplast fusion bypasses biological barriers to the natural allopolyploidization of Citrus, and creates new evolutionary opportuni ties that would be difficult or impossible to achieve by natural or co nventional hybridization.