- I J Froneman and C P Welgemoed
- Institute for Tropical and Subtropical Crops, Private Bag X11208, Nelspruit 1200 South Africa
- 2001
Air layering in South Africa, as in the rest of the world, is the most widely used method for commercially propagating litchis. It is an easy and simple method, but requires large quantities of plant material. Introduction of new cultivars into the industry and selection of promising seedlings in the breeding programme, stimulated the need for other methods of propagation. The use of cuttings, micro and multiple air layering and grafting onto seedling rootstocks were investigated. Grafting I budding onto juvenile seedlings of selected cultivars appears to hold most promise for accelerating the distribution of new material. A respectable 80% – 90% success rate was obtained when several hundred seedlings of three different cultivars were grafted with the most promising cultivars and seedling selections available in South Africa. Cultivar evaluation and the utilisation of rootstocks for tree manipulation will be carried out simultaneously in future cultivar development programs.
Summary:
- Air layering is the most common commercial propagation method for litchi in South Africa and worldwide but requires large quantities of plant material and has limitations such as damage to parent trees and slow propagation cycles.
- The study investigated alternative propagation methods including:
- Cuttings (rooting girdled vs non-girdled branches)
- Micro and multiple air layering (smaller air layers and multiple air layers on one stem)
- Grafting and budding onto seedling rootstocks
- Cutting trials showed:
- Girdling enhanced rooting, but rooting success remained low (up to ~46.6%)
- Best rooting of cuttings occurred from November to February, with HLH Mauritius and McLeans Red cultivars performing better.
- Micro and multiple air layering achieved very high success rates (95-100%) with minimal damage to mother trees.
- Multiple air layering near the stem base resulted in fewer roots and slower growth.
- Transplant losses from mother tree to nursery were minimal.
- Grafting onto seedling rootstocks showed great promise for rapid multiplication:
- High survival rates of 80-90% for rootstocks like McLeans Red, Wai Chee, and Brewster.
- Grafting success rates ranged from 57% to 100% depending on cultivar and seedling selections.
- Best grafting survival occurred during July to October; survival declined significantly from November to February.
- Comparison of propagation methods:
- Cuttings have high multiplication rate but poor rooting and complex techniques.
- Micro air layering is simple, cheap, with fair rooting success and medium multiplication rate.
- Grafting offers uniformity, very good root systems, and good multiplication rate, considered the most effective method for rapid multiplication.
- Advantages of grafting include minimal damage to parent trees, no special equipment needed, and potential for rootstock use to improve traits such as precocity, fruit quality, and pest tolerance.
- Future research directions:
- Acceleration of seedling growth in nurseries.
- Graft compatibility between cultivars.
- Development of juvenile clonal rootstocks with desirable traits like dwarfing and early fruiting.
- Overall, grafting onto seedling rootstocks is recommended as the best method for accelerating distribution of new litchi cultivars and seedling selections in South Africa, alongside continued evaluation of rootstocks and propagation methods.