New Biotechnological Tools for the Genetic Improvement of Major Woody Fruit Species

Abstract

The improvement of woody fruit species by traditional plant breeding techniques has several limitations mainly caused by their high degree of heterozygosity, the length of their juvenile phase and auto-incompatibility. The development of new biotechnological tools (NBTs), such as RNA interference (RNAi), trans-grafting, cisgenesis/intragenesis, and genome editing tools, like zinc-finger and CRISPR/Cas9, has introduced the possibility of more precise and faster genetic modifications of plants. This aspect is of particular importance for the introduction or modification of specific traits in woody fruit species while maintaining unchanged general characteristics of a selected cultivar. Moreover, some of these new tools give the possibility to obtain transgene-free modified fruit tree genomes, which should increase consumer's acceptance. Over the decades biotechnological tools have undergone rapid development and there is a continuous addition of new and valuable techniques for plant breeders. This makes it possible to create desirable woody fruit varieties in a fast and more efficient way to meet the demand for sustainable agricultural productivity. Although, NBTs have a common goal i.e., precise, fast, and efficient crop improvement, individually they are markedly different in approach and characteristics from each other. In this review we describe in detail their mechanisms and applications for the improvement of fruit trees and consider the relationship between these biotechnological tools and the EU biosafety regulations applied to the plants and products obtained through these techniques.

Generation of Transgenic Rootstock Plum ((Prunus pumila L. × P. salicina Lindl.) × (P. cerasifera Ehrh.)) Using Hairpin-RNA Construct for Resistance to the Plum pox virus

“…Such an approach opens up the possibility of producing non-transgenic fruit while ensuring the overall resistance to viral infection using a transgenic ribonucleic acid interference (RNAi) inducing rootstock. The success of this approach, however, has largely depended on the species, the level of expression and the interactions of the small interfering ribonucleic acid (siRNA) with the target gene [15]. For example, the transfer of transgene-derived siRNAs from the transgenic cherry rootstocks to the non-transgenic scions in grafted trees was effective in inducing resistance to the Prunus necrotic ringspot virus [16].…”

A highly efficient organogenesis protocol based on zeatin riboside for in vitro regeneration of eggplant

“…The development of new genome editing technologies in plant breeding has generated a growing interest in in vitro culture for regeneration protocols [13,14]. This is partially due to the difficulties often encountered in plant regeneration, which is a key step in any transformation protocol and a major bottleneck for applying these techniques in many species [13,15]. On the other hand, other breeding techniques, like the development of polyploids without antimitotic products such as colchicine [16][17][18][19], can benefit from regeneration protocols able to induce a certain percentage of plants with changes in ploidy levels.…”

Plant Hybridization as an Alternative Technique in Plant Breeding Improvement

“…Introduction of new traits in plants largely relied on sexual crosses between different genotypes within or between closely related species [1]. However, due to the presence of various reproductive barriers, gene transfer has been restricted to sexually-compatible species, thus limiting the possibilities of modifying and improving crop plants [4]. Many desirable and agronomicallyinteresting traits may only be found in distantly related species or even in unrelated plants [5].…”