IN-SITU HYBRIDIZATION IN ACTINIDIA USING REPEAT DNA AND GENOMIC PROBES

In situ hybridization has been used to probe chromosome spreads of hex aploid Actinidia deliciosa (kiwifruit; 2n = 6x = 174) and tetraploid A . chinensis (2n = 4x = 116). When a species-specific repeat sequence, pKIWI516, was used, six hybridization sites were observed in some acce ssions of tetraploid A. chinensis and all of A. deliciosa. Southern an alysis with the pKIWI516 probe revealed that there are two types of te traploid A. chinensis. Genomic probes from diploid A. chinensis (2n = 2x = 58) did not differentiate the genomes of hexaploid A. deliciosa a nd tetraploid A. chinensis, irrespective of the presence or absence of blocking DNA. The results indicate that the genomes of polyploid Acti nidia species are similar but not identical. The origin of A. delicios a is discussed.