ELUCIDATING THE CAUSES OF FIRMNESS IN BLUEBERRIES (V. corymbosum): CELL WALL COMPOSITION, IONS AND ENZYMES

MONTECCHIARINI, MARINA; VALDERRAMO, L.; GOLLÁN, AGUSTÍN; RIVADENEIRA, FERNANDA; BELLO, FERNANDO; VÁZQUEZ, DANIEL; MARGARIT, EZQUIEL; MORALES, LUISINA; TRIPODI, K.E.J.

Congreso; Congreso de SAIB; 2020

SAIB

Blueberries (Vaccinium corymbosum) have been cultivated in Argentina since the mid 1990 decade and constitute a veryprofitable resource. Most of the production is exported to the northern hemisphere from September to December, when thereis no local availability. Because ripening is non-homogeneous in the plant, considerable volumes of fruit must be stored undercontrolled conditions before being shipped. At the same time, export is mainly by ship in order to reduce costs, which requiresa long transportation time to the final destination. These factors make firmness a very relevant attribute in the blueberry sincea soft fruit is frequently rejected by consumers, giving rise to economic loss. The pursuit of firmer and better-quality blueberriesis a continuous task that aims at a more profitable production. To this end it is essential to understand the biological processeslinked to fruit firmness, which may diverge among fruit tissues. By contrasting varieties with opposing firmness, we were ableto elucidate the events that, taking place at immature stages, lay the foundation to produce a firmer ripe fruit. A deep study ofblueberry skin was carried out, involving diverse comparative analysis such as proteomics, metabolomics, ionomics, hormonelevels and cell wall immunofluorescence assays. In ‘O'Neal’ (a low firmness variety) enhanced levels of aquaporins, expansinsand pectin esterases at the green stage were found to be critical in distinguishing it from ‘Emerald’ (a high firmness variety).The latter featured higher levels of ABA, low methyl esterified pectins in tricellular junctions and high levels of catechin atthis stage. In addition, a greater abundance of XET/H, high content of methyl esterified homogalacturonan, together withseveral mechanisms of cell wall reinforcement such as calcium and probably boron bridges appear to be prominent in‘Emerald’ ripe fruit epicarp regarding ‘O'Neal’. This study highlights the importance of cell wall reorganization and structure,abundance of specific metabolites, water status, and hormonal signaling in connection to fruit firmness. These findings resultparticularly valuable in order to improve the fertilization procedures currently used or in the search of molecular markersrelated with firmness.