Kiwi growing (Actinidia deliciosa) is very recent in Europe. It has been developed following the New Zealand model, using a cultivar (Hayward) and cultivation techniques set up in New Zealand. European kiwi research should investigate specific adaptation problems encountered in our temperate climates.
The aim of the project is to improve cold resistance by breeding for new varieties with a shorter growth cycle (to avoid frost damage in spring and autumn) and by creating rootstocks which are more resistant to winter frost.
The aim of the study was to create genetic variability and to exploit it at different levels to increase the frost resistance of A deliciosa.
In vitro irradiated microcuttings of cv Hayward were successfully regenerated. This material is under observation. Insitu induced parthogenesis by gamma ray irradiated pollen was experimented on cv Hayward. The method appears to be efficient for creating trihaploid plants. Attempts to double the chromosome number of one trihaploid resulted in mixoploid, hexaploid and dodecaploid plants.
The programme of conventional intraspecific hybridization has allowed comparison of breeding value of the four oldest kiwi varieties. The most practical results have been the selection of two female and two male clones which appear very promising.
The peroxidase test based on the fact that activity is higher in females than in males was used to discriminate between the sexes.
In order to create frost resistant rootstock, frost resistance tests were undergone. Some species close to A deliciosa were found to be more resistant. Natural hybrids between A arguta nad A deliciosa have a behaviour rather different to that of the female parent A arguta. Studies on graft compatibility are in progress.
Embryos issued from intraspecific hybridization involving genitors for frost resistance have been successfully grown in vitro.
Conventional techniques of intra and interspecific hybridization will be used, as well as modern biotechnology techniques such as protoplast fusion and in vitro mutagenesis. Cold resistance will be studied in both fields and artificial conditions.
The development of new cultivars will lead to diversification and improvement of fruit quality for consumers. Increased frost resistance will help to regularize yields and to stabilize the producers' income.