Kiwifruit

Abstract

The wide genetic variation among the different species belonging to the genus Actinidia provides the opportunity for developing new cultivars in order to increase the kiwifruit world market variability, which has been limited to few types. The main expected characteristics for new cultivars are the improvement of fruit quality characteristics, abiotic and biotic stress tolerance, regulation of fruit ripening, the production of hermaphrodite plants, parthenocarpic fruits, and the alteration of vegetative habit. Genetic improvement programs are focused on modifying the expression of the endogenous genes, or on transferring foreign genes through both direct and indirect gene transfer methods. Efficient in vitro regeneration systems are indispensable for the recovery of transgenic plants. Optimal results have been obtained in three species of the Actinidia genus because kiwifruit has demonstrated relative amenability to in vitro multiplication; protoplast culture, somatic hybridization, embryo rescue, and the creation of dihaploids lines have also been developed as methods for genetic improvement. Transgenic plants of A. deliciosa have been recovered with some foreign genes of interest: rolABC, rolB, whole T-DNA, osmotin, human epidermal growth factor, soybean -1,3-endoglucanase, and OSH1. Some of these transgenic plants are under field evaluation for biotic stress resistance and growth habit.