Pg. 60-65 Methods for Rapid Propagation of Litchi Cultivars and Selections

The current status of different methods of vegetative propagation of litchi (Litchi chinensis Sann) is reviewed. With the introduction of new cultivars into South Africa and the initiation of a breeding programme, propagating methods other than airlayering which is commercially used, need to be considered. Propagation by seed, grafting, budding, cuttings and stooling were examined as alternative methods for the South African litchi industry. Seedlings are used in the breeding programme, while cuttings, graftings and budding could be utilized for rapid multiplication where availability of vegetative material is limited. Stooling, in addition to airlayering, could be used on a commercial scale to multiply established cultivars. Results obtained with the rooting of cuttings, are reported. Better rooting was achieved with girdled cuttings while rooting success varied with different cultivars. lndole butyric acid (IBA) treatments enhanced rooting and the potential exists for propagating litchis with single node cuttings. A 70- 100% success rate was achieved when topworking 15 different cultivars/selections onto established field-rootstocks for use in the litchi breeding programme. No obvious incompatibility was observed.

Summary:

• The article reviews various methods for rapid propagation of litchi cultivars and selections with a focus on South Africa.
• Air layering is the most widely used commercial propagation method but has limitations such as slow multiplication rates and difficulty in transporting delicate plants.
• Seed propagation is mainly used for breeding and rootstock purposes, not by nurserymen, as seedlings vary genetically and display a long juvenile phase.
• Grafting methods evaluated include approach grafting, side grafting, whip grafting, and bark grafting; all can be technically successful but have variable rates and require attention to stock-scion compatibility and cambial activity.
• Budding techniques such as shield, chip, and patch budding have been explored, but results are inconsistent across regions and years.
• Cuttings (stem cuttings) provide a promising avenue for rapid multiplication, especially when plant material is scarce; successful rooting is influenced by genotype, parent tree condition, wood type, environmental factors, and use of growth regulators like Indole Butyric Acid (IBA).
• Girdled cuttings and application of IBA greatly enhance rooting success; rooting percentages may vary between different cultivars.
• Stooling—cutting a tree back and mounding soil to encourage rooting of new shoots—offers a faster method and superior root system compared to air layering; it yields more plants per area annually.
• The ITSC (Institute for Tropical and Subtropical Crops) initiated work to improve clonal propagation, including trials on grafting and rooting cuttings, and found approach whip grafting and single-node cuttings viable for rapid multiplication of new introductions.
• South Africa’s litchi industry is mainly based on two cultivars; a limited genetic base and short harvesting seasons increase the need for improved propagation methods.
• Overall, grafting and cuttings hold the most promise for accelerating the distribution of new cultivars; further research is required on techniques, environmental conditions, nutrients, and timing.
• Stooling and other alternative methods should be considered for commercial use to meet local industry demands, especially with the introduction of new cultivars and breeding programs.
• The article emphasizes the necessity to develop and apply alternative vegetative propagation methods to address the specific needs of the South African litchi industry.​