Technology fact sheet
- Helps overcome constraints to growth caused by stress such as flooding or soil-borne diseases.
- Grafting can make yield more stable under different stress conditions.
- Farmers can grow tomato in the hot-wet season (offseason) when prices are high.
- Best suited for commercial seedling production by nurseries.
- Effective when high-value tomato varieties are extremely vulnerable to soil-borne diseases and other stress, regardless of the season.
- Enables farmers to grow tomato varieties popular with consumers even though these may be vulnerable to soilborne disease and floods.
- Can help reduce use of agrochemicals and contamination of soil and water bodies.
This graph summarizes the results of a sustainability assessment conducted for this technology. The closer the line is to the outer edge of the diagram, the better the technology performs in terms of the particular criterion
What is tomato grafting?
- Grafting involves the attachment of an above-ground portion of a plant (scion) chosen for high fruit quality or high yield, to the root system (rootstock) of a seedling that is tolerant or resistant to stress caused by disease, nematodes, drought, flooding, heat or salinity.
- Grafting tomato scions onto flood-tolerant and/or soil-borne disease-resistant eggplant rootstocks can increase tomato yields whenever these constraints are present.
- Grafting tomato scions onto soil-borne disease-resistant tomato rootstocks reduces the impact of soil-borne disease in the plant and may provide higher yields than eggplant rootstocks, due to higher scion-rootstock compatibility.
- As grafting is time-consuming and somewhat expensive, many farmers prefer to buy grafted plants from nurseries.
- The grafting technology is best suited for commercial production of grafted tomato seedling in nurseries.
- The necessary components are rootstock seedlings, scion seedlings, pots and/or flats filled with planting medium (soil mix) for growing seedlings, simple grafting tools (razor blades and latex tubes), a grafting healing chamber and adequate water supply. A separate screen house for hardening of grafted plants is useful but not mandatory.
- It is recommended to use a rotating system in the healing chamber with seedlings of different ages, for example, grafting once every three days. This ensures that grafted seedlings are available for sale throughout the planting period. Therefore, new seedlings for scions and rootstocks need to be sown frequently.
- The technology described here can also be used to graft chilli and sweet pepper seedlings for planting in areas where soil-borne diseases and flooding hamper production.
- Outside the grafting season, the grafting chamber can be used as a nursery for non-grafted seedlings of other crops such as chilli, papaya and cabbage.
- Bacterial wilt is a major problem in Lam Dong province in Viet Nam and can result in a 100-per cent loss of the tomato crop.
- Grafting and growing tomato from grafted seedlings was introduced in Lam Dong province in August 2003.
- Since the introduction of the technology, the demand for grafted plants has increased, leading many nursery operators to focus on growing grafted tomato.
- Adoption levels have now reached 100 per cent.
Where it works
- This technology is especially effective in the hot-wet season of tropical countries where production constraints due to soil-borne disease, waterlogging and flooding are high.
- Typical successful adopters are tomato farmers and nursery operators in areas vulnerable to soil-borne diseases and flooding.
- A higher market price for tomato from a grafted plant can only be obtained if a lower-priced alternative is not available, for example, from other regions without the above-mentioned problems.
Constructing a grafting healing chamber
- Select a flat site at an elevation that is not at risk of flooding. Building the chamber in a shaded area decreases the need (and costs) of additional shading.
- Different designs and shapes are possible for the grafting healing chamber (see Figure 1 and other examples in the online version of this fact sheet) but the chamber should meet the needs of newly grafted seedlings, namely low light, high humidity (>85 per cent relative humidity) and temperatures between 25° C and 32° C.
- The material for the chamber can be chosen from what is locally available. A combination of bamboo stakes, PVC pipes, bricks, 60-mesh nylon netting, wood planks and laths, black polyethylene film, transparent polyethylene sheets, silver/ black/ green shade netting and plastic clips, ropes, wire or nails can be used.
- The use of 60-mesh nylon netting is crucial to keep out virus-transmitting insects such as aphids and whiteflies (standard 32-mesh will not exclude whiteflies).
- Double doors reduce the chances for entry of insect pests with workers. However, in smaller and low-cost grafting chambers, double doors might not be feasible. In any case, pests should be eliminated immediately on detection inside the chamber.
- A 2 x 1.5 x 1.75 m grafting chamber with two to three racks can accommodate up to 3,000 seedlings.
- The grafting healing chamber is used for about one week, immediately after grafting.
- Optional: a screen house can be used to grow seedlings prior to grafting and to harden the grafted plants. The screen house excludes pests, enabling growth of healthier seedlings.
Figure 1. Example of a grafting healing chamber with two racks
Grafting tomato seedlings
The entire grafting process consists of 1) growing seedlings for grafting, 2) the grafting procedure including healing and hardening of grafted seedlings and 3) special field management measures after transplanting. In Indonesia, the entire process lasts about 30-33 days from sowing and takes place between September and December, which corresponds to the onset of the rainy season .
1) Growing seedlings for grafting:
- Suitable rootstocks for the grafted seedlings should be selected depending on the situation (see also http://www.vegetablegrafting.org/rootstock-tables/):
- Eggplant rootstocks should be used when flooding or waterlogging is expected. To maintain high yield and fruit quality of the scion varietal, it is recommended to use eggplant accessions EG 195 and EG 203.
- D isease resistant tomato rootstocks should be used only if flooding and waterlogging is not expected. It is recommended to use tomato line Hawaii 7996.
- Since the scion and rootstock stems must have the same diameter for successful grafting (see below), sowing scion and rootstock seeds at the correct time is very important. Growers should take the germination period and the growth rates of the seedling varietals into account and adjust sowing times accordingly.
- I f grafting large-fruited tomato scions on to eggplant rootstocks, sow the eggplant approximately three days before the tomato.
- I f grafting cherry tomato scions on to eggplant rootstocks, sow eggplant and cherry tomato on the same day.
- If grafting tomato scions on to tomato rootstocks, take into account the different growth rates of tomato varietals for proper timing of the sowing.
- It is recommended to grow seedlings in a light, well-drained and pasteurized (heat-treated) soil mix (such as a mix of field soil, well-decomposed compost, rice husk and river sand in a 2:3:1:1 ratio).
- If compost is not available, add 30 g of nitrogen per 100 l of soil mix for tomato or 50 g nitrogen per 100 l of soil mix for eggplant.
- If using a field soil mix, cover seeds with a fine compost to prevent crusting.
- Rootstock seedlings are grown in individual, 6-cm diameter pots or in a big seedling tray (see picture below).
Figure 2. Seedlings in a tray
- Scion seedlings are raised in individual pots or in open flats. If using open flats, space seedlings at least 4 cm apart (to prevent seedlings from becoming tall and spindly).
- If seedlings are becoming tall and spindly, this is due to inadequate light and you should place the grafting chamber in a place with better lighting or reduce the shade.
- Seedlings may be grafted after developing two to three true leaves. The stem diameter should be 1.6–1.8 mm at the cutting point. Typically, this requires 14 to 16 days after sowing.
2) The grafting procedure:
- The scion and rootstock stems must have the same diameter (1.6-1.8 mm).
- Cut the rootstock stem above the cotyledons at a 30º angle. Start the cut as high on the stem as possible.
- Cut the tomato scion stem at a 30º angle, slightly above the cotyledons or first true leaf. It is crucial that the scion's stem diameter matches the rootstock's stem diameter. Select a place on the scion stem to achieve the proper diameter.
- Slide a 10-mm-long latex tube (2.0-mm inner diameter and cut at a 30º angle) over the scion stem. Make sure that the cut angles of the tube and scion are parallel. Push the scion about halfway into the tube (you must leave room in the tube for the rootstock stem).
Figure 3. Adding latex tube to scion
Figure 4. Joining scion and root stock
- Slide the scion (now fitted with the latex tube) over the rootstock seedling stem. Make sure that the cut angles of the tube and rootstock stem are parallel.
- Gently push the scion and rootstock together. If you have kept all the cuts parallel, the scion and rootstock will be in complete contact with one another. The tube will stay on the seedling until it hardens naturally, splits and falls off in the field.
Figure 5. Pushing the scion and rootstock together