Researchers in Nigeria of the National Root Crops Research Institute (NRCRI), Umudike, and IITA, Ibadan, developed the minisett technique to overcome the critical problem of the unavailability of good quality seed yam by improving the rate of multiplication of white yam (IITA 1985). With the technique, the multiplication ratio can increase from the traditional 1:5 to 1:30 (Orkwor et al.
The minisett technique involves the cutting of ‘mother’ seed tubers into small setts (minisetts) of 25-100 g which must possess a reasonable amount of peel (periderm) from which sprouting can occur. The minisetts are treated with chemicals to prevent damage from diseases and pests, planted, and managed to produce small whole seed tubers; these in turn are planted to produce ware
tubers for food.
There is a positive correlation between the size of the minisett and the size of the seed yam produced. This means that minisetts should be cut for a targeted seed tuber size. There are varietal differences in the performance of minisetts; therefore the same size of different varieties may perform differently (Aighewi 1998).
Advantages of Using the Minisett Technique for Seed Yam Production
The minisett technique has been shown to have several advantages over traditional methods of seed tuber production. Some of the advantages are listed below.
- Fewer ware tubers are used as seeds.
- A few tubers of a desired variety can be multiplied rapidly as planting materials for use, sale, or distribution (for example, after periods of natural disasters such as floods).
- The technique is easy for subsistence farmers or seed yam entrepreneurs to carry out.
- From minisetts, tubers in a range of sizes are produced which could be put to different uses – planting material, fresh or processed food, and export. The minisett size can be chosen to produce tubers of the size required for export as food.
- The small tubers produced are better as planting material than cut setts because they do not have cut surfaces and are thus less likely to rot when planted.
- Production of seed tubers from minisetts can be more easily mechanized than other methods of production. With a uniform size of minisetts, equipment used in the production of crops such as potato can be adapted for use in planting minisetts and harvesting seed yam.
- Researchers can rapidly multiply new varieties for distribution or evaluation.
- Crop emergence and establishment are faster with whole seed tubers (such as those produced from minisetts) than from cut seed tubers.
- The whole seeds such as those from minisetts tend to produce stands that are more uniform both in percentage emergence and growth characteristics; this results in a more efficient use of inputs.
- The use of whole seed tubers eliminates the cost of cutting and reduces the spread of disease.