Effects of seasonal climatic variations on physiology and phenology of Litchi chinensis Sonn. In Madagascar

Introduction – The phenology of lychee (Lychee chinensis Sonn.) varies as a function of the develop- are dependent on climatic conditions. The aim of this study was to determine the impacts of climate (temperatures and rainfalls) on the lychee tree development. Materials and methods – Plant physiology and seasons in four lychee production sites in Mada- fruit formation, fruit development and ripening. The used phenological codes were based on the extended BBCH-scale and described the growth stages of the lychee plant using a three-digit numerical system. The analysis of auxin (indole-3-acetic acid – IAA) and abscisic acid (ABA) contents in different plant parts by high-performance liquid chromatography (HPLC), coupled to a diode array detector (DAD), was performed to evaluate potential different physiological dynamics in leaves from branches with or without Results and discussion – The climatic stresses by a reversal of the production phases (stages 5 to 9) toward the resumption of the growth phases (stages 0 to 3). Changes of auxin and abscisic acid contents indicated a sensitivity of the plants to climate variability: the leaves contained about 10 mg ABA 100 g-1 dry weight, what is rather low compared to the concentrations of IAA. Based on the BBCH model, the phenological pattern of lychee followed a more marked evolution by phase reversal at a critical point of time, when the stop code leads to growth anomalies. This evolution is considered an anomaly and no longer represents the normal rhythm of the lychee tree development according to BBCH-scale. Conclusion – Unfavourable climatic conditions such as climatic disturbance may be responsible for the tree hormonal imbalance with potential detrimental effects on lychee cultivation in Madagascar: an accurate understanding of these stages is very important for the correct timing of general orchard management, particularly for disease and pest management.