Mutagenesis and Biotechnology Techniques as Tools for Selecting New Stable Diploid and Tetraploid Olive Genotypes and Their Dwarfing Agronomical Characterization

Abstract

<jats:p>In <jats:italic>Olea europaea</jats:italic> L. subsp. <jats:italic>europaea</jats:italic>, tetraploid genotypes do not exist in nature. Herein, we report the first example of selection of tetraploid olive plants, obtained by combining physical mutagenesis and biotechnology techniques. Stable tetraploid (4<jats:italic>n</jats:italic>) and diploid (2<jats:italic>n</jats:italic>) genotypes were isolated in vitro through shoot-tip fragmentation of two mixoploid mutants derived from the gamma irradiation of self-incompatible Leccino and self-compatible Frantoio cultivars. In this study, the stable mutants FRM5-4<jats:italic>n</jats:italic>, FRM5-2<jats:italic>n</jats:italic>, LM3-4<jats:italic>n</jats:italic>, and LM3-2<jats:italic>n</jats:italic> were characterized in the field for vegetative and reproductive behavior with the aim to use them as varieties or dwarfing rootstocks. The stable 4<jats:italic>n</jats:italic> genotype of Leccino acquired self-fertility whereas the 4<jats:italic>n</jats:italic> Frantoio maintained it. A high and constant yield was showed by LM3-2<jats:italic>n</jats:italic> during 9 years of observation, maintaining the same oil quality as the Leccino wild type (<jats:italic>wt</jats:italic>). Moreover, the LM3-2<jats:italic>n</jats:italic> acquired the capacity to be intercompatible with the diploid mutant Leccino dwarf (LD) and with the Leccino <jats:italic>wt</jats:italic>. This acquired property would allow for a reduction of heterozygosity in the offspring, if crossed with each other for some generations and with the Leccino <jats:italic>wt</jats:italic>, because it is a sort of self-fertilization. When used as rootstocks, both 4<jats:italic>n</jats:italic> and 2<jats:italic>n</jats:italic> Leccino mutants proved to be very effective for reducing the scion size of the high-vigor Canino cultivar, which is well known for its excellent extravirgin oil. Finally, it was demonstrated that the self-grafting of vigorous cultivar caused a reduction in plant size, thus suggesting that it is possible to produce semidwarf plants from vigorous genotypes to consider them in high-density olive orchards.</jats:p>

Osmotin: A Cationic Protein Leads to Improve Biotic and Abiotic Stress Tolerance in Plants

“…Gene transfer technology has become a useful alternative to speed up genetic improvement by correcting defects or conferring tolerance in well-known commercial varieties [ 24 ], and also speeding up the breeding programs, whereas the establishment of suitable novel genotypes by means of traditional crossbreeding requires a great deal of time [ 25 ]. Multiple genes have to be introduced for developing tolerance in plants against stress [ 26 ], such as osmotin, which plays an important role in improving various crop yields by protecting them from various biotic and abiotic stresses.…”

“…In addition, under stress condition, osmotin interacts with other proteins to induce signal flux that enhances the expression of defensive genes by changing the balance between cell death and protein survival [ 25 ]. Most of the osmotin protein is localized in the electron-dense bodies of vacuoles and a minute amount is present in cytoplasm which has been detected in barley [ 28 ].…”

Response of Olive Shoots to Salinity Stress Suggests the Involvement of Sulfur Metabolism

“…Olive ( Olea europaea L.) tree belonging to family Oleaceae, is one of the most popular species of the genus Olea which is used for food purpose [ 1 , 2 ]. Olive is widely grown all over the world, with a great potential for expansion because of its ability to cope with unfavorable conditions [ 3 , 4 , 5 ]. However, most of the olive production (about 98%) comes from the Mediterranean basin [ 1 ].…”

Effect of Grafting on Viral Resistance of Non-transgenic Plum Scion Combined With Transgenic PPV-Resistant Rootstock

“…The proper combination of scion and rootstock, sometimes belonging to various species, enhances the productivity of fruit trees and increases the tolerance/resistance to biotic and abiotic stresses. Grafting also improves fruit quality and provides new superior or dwarf architecture to meet a variety of practical needs ( Rugini et al, 2016 ). The interaction between scion and rootstock is bi-directional.…”