Carbohydrate reserve regulation and fruit productivity in two mango cultivars at high or low planting densities

Abstract

Enhancing fruit productivity in mango orchards often involves increasing the number of trees planted per unit land area, yet higher planting density can lead to reduced yields per tree due to smaller canopies. Non-structural carbohydrate availability and its allocation to reproductive development are critical for tree-level productivity optimisation. This study explores the link between carbohydrate reserves and fruit yields per tree across two growing seasons (2023/24 and 2024/25). We compared starch and sugars in major storage organs, roots and trunk wood, of two mango cultivars, ‘NMBP 1243’ and ‘Keitt’, grown at two planting densities (208 and 1250 trees per hectare) in Australia. Samples were collected from six trees of each cultivar at both densities, at key phenological stages each season. We established baseline carbohydrate reserves influenced by prior cropping, assessed carbohydrate replenishment before the next fruiting cycle, and evaluated carbohydrate usage during fruit growth. Leaf stomatal conductance, density and chlorophyll content were additionally monitored as indicators of photosynthetic capacity. Subsequently, the relationships between fruit productivity and tree carbohydrate dynamics were assessed. The results suggest that ‘Keitt’ exhibits superior productivity capacity due to highly functional leaves and a greater reliance on carbohydrate reserves to support fruiting. ‘Keitt’ could be considered an ‘optimistic’ carbohydrate regulator, utilising carbohydrate resources more e iciently. In contrast, ‘NMBP 1243’ trees tend to exhibit larger vegetative canopies and appear to adopt a more ‘pessimistic’ approach to utilising carbohydrates for fruiting. ‘Keitt’ appears particularly suitable for higher planting density orchards due to its ability to regulate carbohydrate reserves and produce more fruit on a canopy volume basis.