Characterization of a collection of tomato mutant lines in the San Marzano background

Abstract

San Marzano (SM) is one of the most popular Italian tomato landraces, used with the dual purpose of fresh consumption and processing. This PhD research is based on the characterization of a collection of tomato mutant lines that were backcrossed to SM, with different numbers of backcrosses (BC). The lines include variants for alla pigments, (hp-1, hp-2, pd), for carotenoids, (r, at, t, B, B_mob), for chlorophyll (gf), for flavonoids (y), for delayed ripening mutants (Nr, Gr, rin) and five double mutants (r_y, gf_y, gf_r, gf_hp-2, Aft_atv). Three main targets were addressed in this PhD work. - Chapter II: Firstly, we wanted to analyze how the different levels of BC could impact on the genetic distance of each line from SM, due to the distinct parental donors of each mutation, as well as to the linkage drag phenomenon. The collection was phenotyped for aspects of vegetative, reproductive and fruit quality; the majority of times the effects of the mutations were recognizable, however pleiotropic effects appeared sometimes, not easily editable with further backcrosses. - Chapter III: To contribute with a further characterization of these mutation, many of which had already been studied in other different backgrounds, but never compared in a single one, the second target consisted in some metabolic analysis, including polar, non-polar and volatile compounds. This allowed to confer more detailed properties to the mutations under study, both under the nutraceutical and the organoleptic point of view. - Chapter IV: The last aim was to apply the CRISPR-Cas9 technique to reproduce two selected mutations, with the final purpose to easily obtain the desired phenotype with the variations typical of the mutation itself. In doing it, new variants of SM were quickly produced, with interesting added or varied properties, without losing the uniqueness of this traditional variety.