Reflective mulches improve the red coloration of Keitt mango fruits.
Shahak Y., Flaishman M. A., Gussakovsky E. E., Giller Y. E., Ratner K., Zilberstaine M., Winer L.
Author Affiliation: Institute of Horticulture, A.R.O. The Volcani Center, P.O.Box 6, Bet-Dagan 50250, Israel.
Alon Hanotea 55 : 489-494
Abstract : Keitt is one of the major mango varieties in Israel. It is productive and tasty, but suffers from a coloration problem. The fruit remain mostly green until maturation, thus gaining lower prices on international markets. Since light is the major factor regulating the biosynthesis of the red pigments (anthocyanins), we have applied reflective mulches to improve the red coloration. Metallized polyethylene mulches were applied along the alleyways between the North-South oriented rows, about two months prior to harvest in summer 1997 and 1998. The daily accumulated light radiation around the fruit increased by 3-4 fold in the treated trees. At noon time, the non-direct PAR light intensity was 2.3-6.3 fold higher in the fruit vicinity of the treated trees, compared with the non-mulched controls. In addition to its weaker intensity, the light reflected from the natural soil specifically lacked the UV A/B (300-400 nm) part of the spectrum, which is essential for pigmentation. Canopy air temperature was not affected by the mulch. The reflective mulch improved the red coloration of the fruit. The percentage of coloured fruits (having red coverage on more than half of their surface area) was doubled by the reflective mulch in both the 1997 and 1998 harvest seasons. The sugar content (TSS) of the fruit from the mulched trees ranged between 13.5% (green fruit) and 14.8% (red fruit), while in the non-mulched control the TSS was significantly lower (12.7%), regardless of the fruit colour. The reflective mulch treatment had no damaging effects pre-, or post-harvest. The application of two parallel mulches (of 3 m total width) instead of one (1.5 m) along the alleyways did not result in any detected advantage. There were no significant effects of the reflective mulch on either the chlorophyll content or the photochemical quantum efficiency of the fruit skin chloroplasts, suggesting that the red coloration does not depend on chlorophyll degradation.