Disease and climate-resilient vegetables can be cultivated by grafting parts of one vegetable to another, producing a hardy plant that withstands soil-borne diseases and harsh weather, and which can improve nutrient-anaemic diets, experts say.
Vegetable grafting was first recorded in the 1920s in Japan, according to the Helsinki-based International Society of Food, Agriculture and Environment (ISFAE), which estimated more than half of Japan’s vegetables in 2003 were cultivated through grafting, a trend that continues to the present.
Asia’s intensive land use on small farming plots located in a disaster-prone region, coupled with high rates of “chronic” malnutrition caused by lack of nutrients, have made vegetable grafting more common here than in other regions, according to the Taiwan-based Asian Vegetable Research and Development Centre (AVRDC).
“By applying grafting technology, farmers can produce high value and nutritious vegetables [even during harsh weather],” said Joko Mariyono, a scientist at AVRDC.
In many developing countries, food policies mostly focus on under-nutrition (lack of calories resulting in acute malnutrition) and overlook solutions to fight chronic malnutrition, according to the World Health Organization.
The agency estimates at least 170 million children are affected by “stunting” worldwide, a sign of such malnutrition where children are too short for their age.
Increased yields, incomes
AVRDC said tomato farmers in Vietnam and the Philippines have been able to double their production and income through grafting, based on recent internal surveys.
AVRDC has helped the farmers use spliced rubber tubing to graft tomatoes onto aubergine (eggplant) roots, known for their resilience against extreme weather and pests. The vegetable that is being improved, the scion, is removed from its original root and placed onto a new plant’s roots, in this case the eggplant, which is also called the rootstock.
Below are five steps adapted from AVRDC’s guidelines:
1) Sow the eggplant approximately three days before the tomato. Tomato and eggplant stems must be the same diameter (1.6-1.8mm).
2) Cut both the tomato and the eggplant above the first true leaves (cotyledons) at a 30-degree angle as high on the stems as possible. The diameter of both plants must match.
3) Slide a 10mm-long tube halfway over the tomato stem and the other half over the eggplant seedling stem, making sure the cut angles of the tube and stems match. Gently push the two plants together.
4) Move the grafted seedlings into a shaded, humid area (kept moist through condensation from water in floor pans) between 25 and 32 degrees Celsius.
5) Four to five days later, drain the water out of the floor pans to reduce humidity for two to three days. Move the newly-grafted plants into another nursery to grow for 7-8 more days.
Farmers in Vietnam and the Philippines have widely adopted vegetable grafting, while growers in Indonesia and a few countries in the Middle East are considering it. For Susanto, a farmer in Indonesia’s East Java Province who goes by one name, grafting has ended plant diseases that used to decimate his tomatoes. “I [now have] additional income from tomato farming, which previously always failed.”
Grafting is performed by hand with only minimal instruction, said Mariyono. “There is no controversial factor. This technology is suitable with local norms, particularly in Asia.”
But it is not for everyone, noted AVRDC. Grafted vegetables have higher production costs than non-grafted ones and should only be grown in places prone to flooding or soil-borne diseases, according to the agency. The set up - building a special nursery - requires farmers to collaborate, and rootstock seed multiplication is still insufficient to meet grafting’s demand, according to the American Society for Horticultural Science.