Farmers in Kirinyaga are wading off upto 40 percent of tomato pests and tripling yields by grafting tomatoes, offering lessons to the over half a million farmers across the country stuck at production with the traditional disease and pest prone varieties. In Kirinyaga, tomato cultivation has enjoyed a tremendous rise over the years buoyed by its rising demand. Currently over 700 farmers in the county are practising the tomato farming. But even as markets grow, so has been the cases of old and emerging pests and diseases like bacterial wilt which have taken a toll on yields.And due to the economic importance pegged to the crop farmers have over relied on pesticides that have gone on to do more damage than good to the crop and the soil.
The adoption of Tomato is on the upward trend with over 700 farmers in the county now engrossed in the practice with the aim putting to rest the pest and disease challenges that come with the un-grafted tomatoes and getting a share of the economic benefits the grafting technology promises and making a good case for the farmers to cultivate this leading domestic vegetable cash crop in the country.
The tomato grafting technology has come as a silver bullet to the farmers saving them unnecessary expenses in pesticides purchase and creating stronger varieties that can wade off pests.
It is with this realization that a tomato grafting venture has kicked off in the area supported by USAID through Integrated Pest Management and Horticultural collaborative Research Support Programme (IPM CRSP and Hort CRSP) and being carried out by researchers from the Kenya Agricultural Research Institute in collaboration with researchers at Makerere University, Uganda and the Ohio State University, USA with Dr. Monica Waiganjo, the Deputy Director at Kenya Agricultural Research Institute (KARI) Thika, in the lead.
Tomato grafting occurs where the rootstock of a resistant plant to bacteria is joined with the shoot of a more susceptible but high yielding root variety. Waiganjo explained that when a tomato seed is sown or seedling transplanted in bacterial wilt infected soil, the bacterial penetrates through the plant tomato spore or other injured plant parts and moves through the xylem clogging it. She added that this process may not be completed in resistant plant or it may not be affected but such a resistant plant however may not have good edible plant. This is the reason why the susceptible plant is grafted on the resistant plant (rootstock) and this combination gives rise to a bacterial wilt resistant plant with preferred tomato fruits from the top (scion) susceptible plant.
The project is currently benefitting over 700 farmers who are attached to over nine farmer groups in Kirinyaga who are registered within the Giant Kangai Tisa farmer group. The team of researchers has already trained the farmers on wedge grafting, a method of grafting in which the shoot is placed in a stock that is cut in a V shape ensuring that the bark evenly joins that of the stock and then tying the two together, because they are familiar to it although Waiganjo explained that splice grafting,performed by cutting the ends of the scion and stock completely across in an oblique direction, in such a way that the sections are of the same shape,is reportedly much faster and it is the method used in Vietnam. She also noted that although grafting technique is tricky for a beginner, practice over time sharpens the skill. This explains why currently, the Kangai-Tisa farmers are conducting it on their own after the instructions, demonstrations and practice that they have had from the researchers during farmer field school sessions at Kirinyaga.
Kirinyaga County was chosen for its prominence in the country in the area of tomato production mostly dominated by small holder farmers who despite their zeal for success are hindered by the ever increasing challenges like diseases and pests hence the inception of grafting has brought profound relief to them.
The trials are already showing massive improvement not only in resistant of diseases like bacterial wilt but also enhance increased yields and stronger plants with high quality fruits. “From our trials in Kirinyaga, grafted tomato yields are higher ranging from 13.5-67 tons per hectare depending on the graft combination, while the ungrafted ranged from 0.5-1.5ton per hectare. The grafted plants are also more vigorous and disease incidences significantly lower than in the indigenous tomato,” noted Waiganjo.
The success of the project is expected to trickle down to other farmers in the country as currently it is regarded as a pilot project. Waiganjo also added that the technique can also be passed onto other areas of the country by empowering the trained farmers to upscale and commercialize the grafting and high tunnel technology through microfinance and encouraging private entrepreneurs through cost sharing training.
“Through the (IPM CRSP) project, the method was borrowed from our regional collaborators at Makerere University, Uganda where tomato grafting was being carried out using indigenous solanacea plants. In Kenya tomato lines bred at KARI-Thika, wild cherry tomato, var. Mt56 and Solanum incanum have been tested and proved promising,” noted Waiganjo. She also highlighted that grafting however is not a new technology since it has been practiced a lot in fruit tree seedlings for reduced fruit maturity period and dwarfing the tree in avocado and mango while in passion fruit, grafting has been done here in Kenya to control disease.
“Tomato grafting is relatively new in Kenya and many other countries in sub-Saharan region as opposed to other countries like Vietnam, where over 90 percent of tomatoes grown there are grafted mainly for plant vigour”. However the scientists added that although in other places tomato grafting is done for plant vigour, the Kirinyaga project’s main objective is to control bacterial wilt although other benefits emanate from the practice. “We have also observed higher plant vigour in grafted plants than ungrafted ones and over 80-90percent plant survival of the grafted compared with un-grafted that recorded 0-5 percentage survival,” said Waiganjo.