Filogènia i variabilitat genètica de les varietats tradicionals de tomàquet (Solanum lycopersicum L.) Montserrat/Pera de Girona i Penjarestratègies per a la millora de la seva qualitat organolèptica

Resumen

Tomato landraces are highly appreciated by consumers in the market. The main reasons are the presumed superior organoleptic quality with respect to modern cultivars, as well as the widespread perception that landraces are original varieties with unique agromorphologic characteristics. Nevertheless the amount of intravarietal genetic variability and its effect on important economic characters is unknown. With the aim to understand the attributes that singularize each variety and to design strategies to boost them on quality markets, a complete characterization of catalan landraces Montserrat, Pera de Girona and Penjar has been conducted. A previous survey of more than 200 accessions allowed us to select representatives of the intravarietal genetic variability of each landrace. Selected accessions were studied on an agromorphological, chemical, sensory (a sensory panel has been trained with this purpose) and molecular (AFLP) basis. Results show that while each landrace has unique traits that differentiate them from others, there is a great heterogeneity within landrace for all the traits recorded. Montserrat and Pera de Girona can be separated only using external fruit morphology traits. A great intra-varietal heterogeneity and overlapping among accessions of both landraces exists for the remain agronomic, morphologic and organoleptic traits (each landrace has not a distinctive sensory profile). Furthermore both varieties have the same genetic background, and the wide variation observed is based on narrow genetic diversity. Penjar landrace is characterized solely by its long shelf life and the small sized fruits. For the remaining characters (including molecular data) intra-varietal diversity is very large. Long shelf life is due to the presence of the ripening mutant alcobaça (alc) (replacement of thymine by adenine in position 317 of the coding sequence of the NAC.NOR gene) in combination with the reduced size of the fruit. The great heterogeneity for sensory attributes among accessions of the same landrace restricts its consolidation on quality vegetable markets. For this reason a breeding program has been conducted in order to obtain pure lines that combine good organoleptic and agronomic characteristics with the unique fruit morphology of each landrace. Breeding lines Punxa (Penjar variety), Sant Jeroni (Montserrat) and Montgrí (Pera de Girona) have been obtained with this approach. Moreover we have studied the effect of postharvest on Penjar tomato aroma, which is a determinant attribute for consumer acceptance. Through sensory analysis we have identified that the dominant aroma of this variety, described as sharp-floral, increases in the early stages of postharvest, reaching its maximum at 2 months. Absence of cis-3-hexanal and the rearrangement of the relative concentrations among volatiles with high impact on tomato aroma would be responsible for this particular behavior. In conclusion, the studies presented in this thesis show that intra-varietal genetic diversity existing in catalan tomato landraces affects almost all traits, both sensory and agromorphological. This high variability within landrace for sensory attributes threatens the success that those varieties have among consumers, so different strategies have been developed in order to improve the genetic and environmental components affecting organoleptic quality of Montserrat, Pera de Girona and Penjar landraces.