Innovative Techniques to Reduce Chilling Injuries in Mango (Mangifera Indica L.) Trees under Mediterranean Climate

Abstract

As a tropical tree, mango (Mangifera indica L.) cultivated in Mediterranean climate needs protection against low temperatures. The aim of this work is to study the effect of traditional individual protective canopy protection systems in comparison with innovative typologies designed for this experiment on the physiological response of young mango trees during the cold season. We selected 25 four-year-old mango trees cv ‘Glenn’. Trees were divided into five different groups: not covered trees (NC); trees with windbreak protection using a shading net (SN); trees with windbreak protection using non-woven sheets (WB); fully covered trees using non-woven sheets (FC); fully covered trees with non-woven sheets and the addition of a 'heat exchanger' device (FC+). Their canopies were fully covered (FC) and (FC+) or enclosed by a hand-made individual windbreaks (SN and WB). We studied the evolution of temperature inside the canopy and evaluated the threshold of damage on leaves and shoots. We also monitored soil temperature under the trees. Precision self-made data loggers were assembled. A "heat exchanger" was realized for this experiment to try to recover heat from the ground and place it under the canopy of the plants. It was made with a 50 cm U-shaped aluminum pipeline using recycled materials; this was placed horizontally, 50 cm deep in the soil with one of two extremities above the soil and the other within the canopy. NC trees were damaged by cold temperature. More particular, the young shoot was injured by necrosis followed by fungal disease. The same behavior was observed in SN and WB when the canopy was only enclosed by the protection whereas FC tree shoots were intact. Non-woven sheets preserved intact the shoots only in the FC trees, as the canopies were completely covered by a closed space because the leaves and shoots were isolated from the outside. The ‘heat exchanger’ device increased, however minimally, the temperature in the closed space containing the canopy. The use of non-woven sheets, covering completely the canopy, allowed to preserve the shoots for future tree development.