This Research Topic is part of the New Developments in Agrobacterium-Mediated Transformation of Tree Fruit Crops series:
New Developments in Agrobacterium-Mediated Transformation of Tree Fruit CropsTree fruits are essential part of human diet and as such are valued and produced in all regions of the world. Intensive fruit breeding programs exist to increase availability and variability of cultivars for fresh consumption and those used by food processing industry. Increased investments leading to higher acreage for growth and tree fruit improvements driven by the demand from growing human population, resulted in worldwide production of tree fruit crops that exceeded 650 million metric tons in 2014. Just in the USA alone, the production value of tree fruit in 2017 was over 20 billion dollars.
Within the last 20 years, Agrobacterium-mediated production of transgenic plants has become an important part of tree fruit breeding programs. As opposed to conventional breeding, this methodology allows introduction of single gene into the genome of already existing elite cultivars without modification of other commercially important traits. Most of the tree fruit crops have long juvenility periods and the use of pollination-based crossing can only be a part of long-term projects that are not funded very often. Agrobacterium-mediated transformation significantly shortens the time for introduction of new traits making this process more precise as there is no need for out-crossing of undesirable traits. Other features of tree fruit crops like complex reproductive biology, sexual incompatibility, nucellar polyembryony, and high heterozygosity that are obstacles in conventional breeding are overcome with the use of Agrobacterium.
Transformation is key to the application of most of the new breeding technologies to tree fruit crops. However, rates of transformation and regeneration of transgenic plants remain low and the entire process can be inefficient in these species. Despite these obstacles, much progress has been made in this area. Many species have been transformed with genes to improve tolerance/resistance to diseases, alter development and architecture of plant, modulate hormonal balance, and control production of secondary metabolites. In some cases, newly created phenotypes were the results of modulation of activity of host’s gene by anti-sense RNA, dsRNA, or miRNA. Intragenic plants carrying either genes or simple stretches of DNA of related species were also produced with the help of Agrobacterium. However, several aspects of genetic transformation achieved in other types of crops or model species have not been reached for tree fruit crops.
This Research Topic aims to cover new developments in the field of Agrobacterium-mediated transformation of tree fruit crops. We welcome manuscripts dealing with:
• Transformation of recalcitrant species through modulation of activity/introduction of genes affecting plant regeneration
• Employment of Agrobacterium strains with different transformation capabilities
• Production of cisgenic fruit trees
• Gene silencing through application of siRNA, miRNA, or amiRNA methodology
• Transformation as a tool in FasTrack breeding
• Ectopic expression of genes leading to novelty traits
• CRISPR-mediated genome editing
• Other new approaches to tree fruit transformation