Understanding the horticultural properties of citrus rootstock trees used for seed production to ensure a continuous seed supply

Citrus rootstocks are a key aspect for the success of commercial citrus plantings.
With seeds being the main propagation method thereof, it is important to maintain and expand seed production.
The aim was to understand the horticultural properties of the main rootstock cultivars of South Africa.
Trials were conducted over two seasons on rough lemon (Citrus jambhiri), ‘C-35’ and ‘Carrizo’ citrange (C. sinensis × Poncirus trifoliata), ‘X-639’ (Cleopatra mandarin (C. reticulata) × P. trifoliata), ‘Swingle’ citrumelo (C. paradisi × P. trifoliata), ‘M×T’ (Minneola (C. paradisi × C. reticulata) × P. trifoliata) and ‘US-812’: sunki mandarin (C. reticulata × P. trifoliata) trees.
Fruit growth patterns were similar amongst cultivars, but time of maturity differed as well as larger fruit producing more seeds. ‘Swingle’ had the highest average seed number per fruit, while ‘US-812’ had the lowest.
For rough lemon, 93% of the seeds developed into mature seeds, with ‘Carrizo’ citrange and ‘X639’ having the lowest ability (59-56%, respectively). Trends indicated differences in fruit number between seasons with an overall increase over three seasons, except for rough lemon and ‘X639’ showing a decrease in the second season.
Furthermore, there was clear yield differences between rootstocks.
Quantification of seed number per fruit was found to be a valuable tool to aid in forecasting when a crop estimate is done.
In addition, these results provide valuable cultivar-specific information to assist future planning for rootstock seed production, i.e., the number of trees needed per cultivar to ensure that the required seed supply is met.

XV International Citrus Congress

J. Niemann, P.J.R. Cronje

fruit growth, propagation, Poncirus trifoliate, rough lemon, seed quantity

https://doi.org/10.17660/ActaHortic.2026.1448.103