Early detection of date alternate bearing disorder based on physiological marker of carbon allocation and evaluation of the disorder using trehalose as allocation modifier

The carbohydrate evaluation of organs (fruit, leaflet and root) at important physiological stages (three peaks of fruit abscission, harvest and before flower induction) on 60 'Mazafati' date palm (Phoenix dactylifera L.) trees in five groves with a history of alternate bearing disorder showed that leaflet starch content before flower induction was the best physiological marker for early detection of this disorder based on both the biennial bearing index (BBI) and fruit bunch number. The differences in carbohydrate between organs in different loading trees were not due to differences in the chlorophyll pigments and photosynthesis rate and were the affect of different loadings on source-sink regulation. The 2-year leaf spray of trehalose disaccharide before flower induction stage on Off trees by activating oxidative stress, increasing leaf hydrogen peroxide index, indicated that these loading differences were due to changes in the allocation of carbohydrate types between organs at this stage. The changing carbohydrate allocation pattern in favor of increasing the leaflet starch compared to other two organs before flower induction by trehalose treatment while increasing flower induction in the Off trees, increasing the bunch number, resulted in controlling the alternate bearing to improve annual production indices and preserving the physicochemical properties of the fruit consistent with the non-alternate bearing trees.