Embryo rescue from interspecific crosses in the genus Actinidia (kiwifruit)

Within the framework of a broad program of interspecific crosses involving different Actinidia species and ploidy races, we carried out an assay of interspecific hybridization using a small number of the Actinidia species available in European repositories. Our aim was to conduct a preliminarily assessment of the degree of crossability occurring in the genus and the effectiveness of different techniques and media in rescuing interspecific hybrids. A set of culture media was developed to replace the hybrid embryo's deficient endosperm to ensure survival of the embryos at the globular and heart stages. In several crosses immature embryos that reached the torpedo stage were rescued when incubated in the proper media. The embryo rescue was the unique tool which led to hybrid plantlets for four crosses: A. kolomikta x A. chinensis, A. polygama x A. valvata, A. arguta Issa x A. polygama and A. kolomikta x A. deliciosa. Flow cytometry was used to check the ploidy level of the parental genotypes and the progeny. A wide interspecific crossability was found in Actinidia that involved species belonging to the different sections on the basis of traditional taxonomy.