Hormonal Regulation of Avocado (Persea americana) Across Altitudinal Gradients

ABSTRACT Avocado (Persea americana) stands out as one of the most significant crops globally. Due to its abundance in essential nutrients and phytochemicals, its consumption and commercialization have notably surged in recent years. The interplay between genotype and environment profoundly influences fruit maturity dates and physicochemical attributes. This study aimed to assess the transcript levels of genes involved in hormone regulation and biosynthesis in avocado fruits, correlating their expression with the crop's physiological characteristics across varying altitudes during maturity and ripening stages. The study focused on five prevalent avocado varieties: Fuerte, Hass, Pinkerton, Lambhass, and Reed. Sixteen genes participating in diverse metabolic pathways and five hormones: Abscisic acid, Jasmonic acid, Salicylic acid, Gibberellic acid, and Zeatin were quantified over the harvesting season across seven locations in Lebanon. Results revealed a notable correlation between the expression of certain genes and hormone levels in the tested varieties, contingent upon both variety and location. Phytohormone quantification exhibited significant variations across locations compared to varieties. Additionally, physicochemical characteristics were evaluated, with principal component analysis demonstrating a positive correlation between some quantified phytohormones and maturity indices among varieties and locations. This study significantly advances our understanding of the intricate relationship among phytohormones, altitudes, fruit maturity, and ripening processes across five of the most common avocado varieties.