The use of grafted vegetable seedlings is on the increase in South Africa, particularly in response to deteriorating water quality, as grafted rootstock provides a measure of resistance to fungal disease and fluctuating salt levels. One of only two nurseries in South Africa with the capability to graft vegetable seedlings is MultiGrow, which formed a joint venture with the Dutch enterprise Grow Group in 2013.In 2016 the nursery received Good Seed and Plant Practices (GSPP) accreditation, of which the main purpose is to prevent Clavibacter michiganensis subsp. michiganensis (bacterial canker or ring rot) infection, mainly on tomatoes.
The nursery was founded in 1947 to provide conventional vegetable seedlings to commercial growers and still performs this function under the name of MultiPlant. Brothers Francois and Len du Toit together with their partner Jannie Fourie decided to branch out to grafting seedlings, a delicate operation carried out by a team of female employees who have received GSPP training.
“South Africa’s water quality has deteriorated a lot which is the big reason to use grafted cucumber seedlings. There’s been solid growth in the use of grafted cucumber seedlings for five years. At the moment we’re seeing an increase in demand for grafted tomato seedlings because of the risk of Fusarium race 3 which has become more prominent over the last 5 years,” explains Len du Toit. The use of watermelon and melon seedlings is their second largest grafted seedling category as it obviates the need for new fields that are uninfected by soil-borne diseases.
The nursery employs Rijk Zwaan’s tomato rootstock Shelter RZ F1, amongst others, that is Fusarium and Ralstonia solanacearum resistant. Cucumbers, melons and watermelons are grown on the Ferro RZ rootstock.
Chrysanthemum roots poking out of MultiGrow's own patented pressed blocks
To manage the cost of imported materials, particularly black peat which is a limited natural resource, Jannie Fourie, who is responsible for commercial and technical market development at MultiGrow, and Len du Toit developed their own growth medium for use as pressed blocks. They have patented their mix, with interest from Europe. They grow their grafted seedlings, as well as other high-value seedlings like the chrysanthemums they grow on from cuttings received from Kenya, in these pressed blocks, thereby reducing their use of polystyrene seedling trays which cause a lot of pollution when discarded. (They still use the polystyrene seedling trays for conventional vegetable seedlings like brassicas, spinach, celery, parsley and onions. They give away tonnes of their discarded trays to be used, mixed with cement, in building construction.)
The recipe of their patented mix is adapted to the eventual growth medium of the seedlings, whether coconut coir or wood shavings, or soil with a high clay percentage.The advantage of these pressed blocks is that seedlings don’t have to be pulled out for replanting and growers speak with praise of how roots from seedlings grown in these blocks penetrate into their eventual growth medium. “The mix is designed to entice the roots outwards,” comments Fourie.
“Grafting vegetable seedlings is tricky and to get everything right from A to Z is difficult. For that reason we decided to team up with Dutch specialists,” Du Toit says, to which Fourie adds: “The single most important factor is hygiene.”
After the surgical procedure of grafting, seedlings go to recovery rooms where the fusion is encouraged in an atmosphere of 100% humidity. Thereafter seedlings are moved to the greenhouse where they spend seven to ten days.
Their Cravo greenhouse is the only one in South Africa with a pitched roof. There are three layers to the roof, which can open, to give optimal control of light intensity, temperature management, air ventilation as well as keeping out insects and pests like Tuta absoluta. Despite all of these measures, the grafting of seedlings is such a delicate operation that they nevertheless factor in losses of around 30% during the process.
The days spent here in their greenhouse, where the seedling grows on in an ideal climate, is growing time reduced for the farmer, especially during winter. They also provide big seedlings of cucumbers and peppers in 20 cm pots.The photo, right, shows cucumber plants of the same age in a commercial production greenhouse (not that of MultiGrow). Those on the left are dependent on their own roots, plagued by fungal soil-borne disease, while those on the right thrive on resistant Ferro RZ rootstock.
The use of grafted vegetable seedlings is becoming increasingly well-known to South African growers. The factors motivating the use of vegetables grown on resistant rootstock are pressing ever stronger on South African growers.
For more information:
Jannie Fourie, Len and Francois du Toit
MultiPlant
Tel: +27 12 250 2500
Email: len@multiplant.co.za