Tomato, Solanum lycopersicum L. is one of the most important cultivated crop plants worldwide (Klee and Giovannoni, 2011). Tomato fruit has high quality nutritional values and is an important source of nutrients ( Raúl et al. 2016). Around 177 million tonnes of tomatoes are produced per year in the world . However, around 25-42% of the yield is lost during postharvest (FAOSTAT, 2014). Rapid softening and pathogen attack are the main causes reducing the shelf-life of the fruit. Therefore, delaying these processes is one of the major targets in fruit breeding programmes
Tomato is a well-studied model of fleshy fruit. Previous research on this model revealed that softening involves changes in CW integrity, in cell turgor, fruit-water status, hydrostatic pressure, the accumulation and distribution of osmotically active solutes among other physiological process (Goulao & Oliveira, 2008) . Research on this area focuses on introducing changes in the expression of specific cell wall modifying enzymes (CWME) that target major cell wall components (such as pectins and cellulose) but there is a lack of knowledge on how minor components (such as callose) can affect fruit traits such as firmness, cell turgor or accumulation or distribution of osmotically active solutes (callose can alter symplastic communication).
In this direction, we proposed to undertake a biotechnological and genetic approach to modify callose levels in the latest stages of fruit development. The modification would result in a modification of the callose degradation in the last developmental phases of the ripening, that could modify cell wall mechanical properties, improving the texture, firmness and, in general, the shelf-life of cultivated tomatoes. In this context, our specific objectives were:
1). To generate tomato plants with modified callose levels at the latest developmental phases of fruit ontogeny.
2). To characterize changes in cell wall composition related to differences in callose levels.
3). To determine the physic-mechanical properties of fruit cell walls with different callose levels.
4). To determine the impact of callose on the development and the softening process of tomato fruits
With regards to the results of the project , the current outcome is a novel bioinformatic tool and knowledge to use in the selection of genes involved in fruit ripening. As a long-time outcome, we also expect to obtain plants producing fruits that maintain their firmness for a longer period of time, thus with reduced susceptibility to mechanical damage and pathogen attack during the postharvest period. This achievement will have a positive impact on the European Union economy by optimizing processes such as the frequency of harvesting, the handling and the transport procedures. It will also impact on human health and food security by reducing losses and the spreading of pathogens that thrive in mature soft fruits.
