Avocado (Persea americana cv. ‘Hass’) Fruit Mineral Composition at Canopy Level towards Sustainable Quality

Abstract

Sustaining avocado fruit quality is crucial to maintain customer satisfaction and confidence. Among fruit qualities, mineral nutrient composition is an important contributor to postharvest robustness. Towards better understanding and addressing variability within the plant canopy, ‘Hass’ fruit from across seven orchard blocks were individually characterised. From five representative trees in each block, five fruit were harvested (one from each of five positions: top (sun-exposed), bottom (shaded), middle (shaded), East (sun-exposed), and West (sun-exposed)). Fruit dry matter was significantly higher (p ≤ 0.001) in fruit from the top, East, and West sun-exposed positions. No significant (p > 0.05) effect of position was discerned for fruit weight at harvest or for either stem end rot (SER) or body rot (BR) incidence at eating soft. Shaded fruit had significantly higher (p ≤ 0.05) [N], [K], [Mg], N:Ca, K:Ca, and K + Mg:Ca in their flesh. Significant negative linear correlations (p ≤ 0.001) were obtained between fruit DM and flesh [N] (r = −0.75), [K] (r = −0.67), and N:Ca (r = −0.57). SER and BR incidence were significantly positively correlated (p ≤ 0.01) with flesh and skin mineral ratios of N:Ca, K:Ca, Mg:Ca, and K + Mg:Ca. Skin and flesh [Ca] were significantly negatively correlated with SER (r = −0.51, p ≤ 0.01) and BR (r = −0.74, p ≤ 0.001) incidences. Soil cation (Ca, Mg, K) availability (%base saturation of cation exchange capacity (CEC)) was not (p > 0.05) correlated with skin or flesh mineral concentrations or ratios. Considered collectively, results suggest that selective harvest of sun-exposed fruit with inherently lower mineral nutrient ratios yields relatively robust fruit. Such fruit lots should better tolerate the rigours of harvest and postharvest treatment and handling. In this context, they should better maintain quality upon passage through long, in terms of accumulated time-temperature increments, export supply chains. In contrast, shaded fruit could be directed into shorter domestic supply chains. As a harvest strategy, segregating fruit lots from harvest could underpin the quality offered to consumers at the end of ‘short’ and ‘long’ supply chains.