Abstract

Emadeldin H.E. Konozy , Mathilde Causse and Mireille Faurobert

Excessive softening is the main factor limiting fruit shelf life and storage. It is generally acceptable now that softening of fruit which occurs during the ripening is due to synergistic actions of several enzymes on cell wall polysaccharides. As a subject for this study, we have assayed some glycosidase activities using 3 tomato cultivars (Lycopersicon esculentum) contrasted for their texture phenotypes; the cherry tomato line Cervil (Solanum lycopersicum var. cerasiforme), a common taste tomato line Levovil (S. lycopersicum Mill) and VilB a modern line, large, firmer and with good storage capability. Four glycosidase activities namely α-galactosidase, β-galactosidase, β-mannosidase and β-glucosidase were extracted from tomatoes cell wall of the three species. Cell wall protein from fruits was extracted and compared among the three cultivars at the following stages; 14 days after anthesis (14DPA) fruit; 21 days after anthesis (21DPA), turning (breaker), red and over ripe. Glycolytic activities were compared among these cultivars at the precited developmental stages, where gross variations were noticed from stage to stage and also from species to species in accordance with the fruit firmness status. Interestingly, VilB cultivar, the firmer among the other two, though possessed the highest total protein content, exhibited the lowest enzymatic activities. Taken together, these results may therefore allow us to conclude that studies of glycolytic activities in a single tomato cultivar cannot be generalized to all species. Thus, the correlation between tomato softness and the glycosidase activities may affirm direct involvement of these enzymes on fruit development and softening)