Relationship between the incidence of sunburn fruits of pineapple ´MD-2´ and its morpho-physiological and biochemical development

Cuba annually exports pineapple as fresh fruit to European markets, however, the tropical conditions in which pineapple cultivation takes place cause burns on the fruit, mainly in the summer months (June-August). Sunburn damage causes economic losses by subtracting the commercial value of fresh fruit. In this work, the phenomenon of sunburn in pineapple fruits (Ananas comosus var. comosus) of the ‘MD-2’ hybrid was characterized through a morphological, physiological and biochemical study of the fruits produced in the months with the highest incidence of this problem. The degree of burns on the fruits was evaluated at 90, 120 and 150 days after floral induction (DAFI). The exterior and interior temperature of the fruits in the east and west sides of orchard was evaluated during 9 h (8:00–17:00). Additionally, morpho-physiological and biochemical variables of the fruits were evaluated during their development. The temperatures on the surface of the fruits fluctuate between 45 and 50ºC, being higher on the west side where they exceed 42ºC inside. Sunburn on the fruits only appears during the last month of development and with a higher incidence on the west side. This increase in burns coincides with the time of physiological maturity of the fruits and the decrease in chlorophyll concentration and a marked increase in antioxidant enzymatic activity in response to the stress that the fruits face.