The History And Current Status Of Genetic Transformation In Berry Crops

Cultivated strawberry (Fragaria x ananassa) and Rubus berries, raspberry and blackberry, are small fruits highly appreciated by consumers and worldwide cultivated. The polyploidy nature of these species, their high heterozygosity, and the lack of natural resistance to several pests are the main constraints to the development of improved genotypes by conventional breeding. In recent years, genetic transformation has demonstrated to be a powerful tool to overcome these limitations. In this chapter, the current state of genetic transformation technology in Fragaria and Rubus spp. is reviewed. The feasibility of strawberry to regenerate in vitro has allowed the development of efficient transformation protocols for both cultivated and the wild strawberry Fragaria vesca. Important traits such as photoperiod requirements for flowering, fungal tolerance, biotic stress tolerance, and fruit shelf life have been manipulated in transgenic strawberry plants through the introduction of different genes. Furthermore, tools for the development of intragenic plants, containing chimeric genes from the own species and devoid of marker genes, have been generated. By contrast, the recalcitrance of Rubus tissues to regenerate in vitro has impeded the development of robust transformation protocols in these species, although a few number of studies have successfully obtained transgenic plants carrying genes of interest. Main achievements, limitations, and future prospects of genetic transformation in both genera are discussed.