Improved methods to estimate the optimized inflorescence size for ‘Rose Red’ litchi fruit set

Litchi (Litchi chinensis) has separate female and male flowers within individual inflorescences, in which fruit set and fruitlet development take place.
In certain litchi cultivars, because of the assimilate competition between new fruitlets (from female flowers) and male flowers, inflorescence size is therefore assumed to be a key factor for fruit bearing capacity. ‘Rose Red’ litchi is one of the most popular commercial cultivars on Taiwan, yet its unstable fruit set has posed a challenge for growers.
Thus, the objective of this study was to understand the relationships between inflorescence size (indicated using length) and fruit set number in ‘Rose Red’ litchi for optimizing production.
We integrated nonlinear regression using Gaussian’s fit and resampling techniques with data collected at 11 weeks after female flower full bloom from ‘Rose Red’ litchi trees located at two orchards on southern and central Taiwan, Chuchi and Fenyuan, respectively.
Our results showed that the fruitlet number was significantly correlated with the length of inflorescences at the Chuchi orchard (n=100, R²=0.560, P=0.033); the model suggested that 22 to 23 cm was the range of optimal inflorescence length for the best fruit set in ‘Rose Red’ (2.1-3.2 fruitlets panicle^‑1) under 95% bootstrap confidence intervals.
However, for ‘Rose Red’ litchi in Fenyuan, there was no significant correlation between inflorescence length and fruitlet number using the same approach in this study (n=123, R²=0.059, P=0.562). The results suggest fruit set in ‘Rose Red’ litchi is intricately regulated and that other factors, in addition to the competition with inflorescences for resources, affecting fruitlet quantity await investigation.

IV Asian Horticultural Congress – AHC2023

Jen-Yu Chang, L. Tang, Yi-Ting Zhang, Jer-Way Chang

Litchi chinensis, fruit, crop load, inflorescence length

https://doi.org/10.17660/ActaHortic.2024.1404.8