Techniques for Tomato Grafting - Purdue Extension

1 HO-260-W. V E G E TA B L E G R A F T I N G. Techniques for Tomato Grafting Authors: Wenjing Guan Vegetable Grafting has attracted Tomato cultivar selection (including the selection and Steve Hallett growers' attention as an approach to of organic seeds). This publication intro- control soilborne diseases and improve duces Tomato Grafting Techniques that are crop yield. By Grafting scion plants that particularly suitable for small-scale pro- have desirable fruit characteristics onto duction. rootstock plants that have disease resis- Successful Tomato Grafting includes three tance, stress tolerance, or vigorous root steps: system characteristics, grafted plants 1. Raising healthy seedlings combine beneficial traits from both the (pre-graft). Horticulture scion and rootstock plants.

2 And Landscape 2. Grafting Many growers who are interested in Architecture growing grafted tomatoes may be hindered 3. Post-graft plant healing by the high cost of already grafted plants. Each of these steps (discussed in detail on Growers may prefer to graft their own next page) is important to ensure the final Tomato plants to reduce costs or increase success of the graft. 1. Vegetable Grafting Researchers at Ohio State University have reported on the time from seeding to Grafting size in Eighteen Key terms Rootstock and Five Scion Tomato Varieties: Seedling Grafting A cultural practice that helps Growth Rates Before Grafting and Success in Grafting control soilborne diseases, improve abiotic stress the Ninety Variety Combinations in the Midwest tolerance, and enhance crop yield.

3 It is commer- Vegetable Trial Report for 2014 ( Purdue Extension cially used on solanaceous and cucurbit crops. publication 16-18-14), available from the Education scion A plant that has desirable fruit charac- Store ( ) or at teristics. rootstock A plant that has desirable disease We recommend you perform an on-farm test with a few resistance, stress tolerance, or vigorous root of the rootstock and scion seeds of the specific varieties system characteristics. of interest to determine how many days you need for meristem Plant tissue that contains undiffer- rootstock and scion plants to reach Grafting size. If entiated cells from which growth begins. Also conducting a test is impractical, use information from known as growing points. the Ohio State report, and remember that most root- stock and scion varieties can be planted on the same adventitious roots Roots that develop from day.

4 Stems. The growth rate may be moderately adjusted after seed cotyledons The leaves that first emerge from germination by manipulating temperature, light inten- a seed. sity, and water and fertilizer application rates. Although having identical stem diameters of rootstock and scion plants is desired, you may still achieve a high survival rate despite some dissimilarity in stem diameter. Also, Pre-graft: Scion and Rootstock you can cut plants slightly higher or lower on the stem Seedling Production to select size-matched areas of the stem to graft. Raising healthy scion and rootstock plants is the first If plants are actively growing, reduce watering before step to Grafting success. Provide optimal seed germina- Grafting to prevent too much water going up the stem tion and growth conditions for both rootstock and scion and pushing the scion off.

5 However, it is important to plants. Tomato 's ideal germination temperature is make sure the potting medium is moist before Grafting . around 85 F. You may need a heating mat to germinate For early-season high tunnel/greenhouse Tomato pro- rootstock and scion seeds in the early spring. Do not duction, producers often grow Tomato plants to a large graft plants that show disease symptoms or are severely size before transplanting into the ground. It is reason- stressed during germination and early growth. able to start rootstocks in large planting pots. Scion You can greatly enhance the efficiency of Grafting if you plants, however, can grow in smaller sized cells, because produce uniform seedlings. Grow rootstocks and scions they will only grow in the medium until Grafting . that have similar stem diameters at the time of Grafting .

6 Although growing scions in smaller cells could save Since germination and growth rates vary among variet- greenhouse space and reduce the cost of materials, you ies, you often need to plant the rootstocks and scions at must graft plants before the plants outgrow the cells. different dates to achieve these similar stem diameters. Growing scion plants in standard planting trays with However, there is no general rule for planting one seed 72-cell size works well for the purpose. type earlier than the other, because several factors influence the relative germination and growth rate of the two plants, including different rootstock and scion combinations, environmental conditions, and seed quality. 2. Vegetable Grafting Grafting You can successfully graft Tomato seedlings with a wide range of sizes.

7 However, plants at a younger stage generally heal faster and require less stringent conditions for post-graft plant healing. At a minimum, the stem diameters of both rootstock and scion must be at least millimeters the small- est Grafting clips are millimeters. Grafting will require silicone Grafting clips, which come in diameters from to millimeters. You can also use side A. Grafting clips (which are often used for Grafting cucur- bits) to graft larger Tomato plants, but they are more expensive. Tomato plants normally need two to three weeks to reach a stem size of to 2 millimeters after sowing. The best way to determine if the timing is right to graft is to put a Grafting clip on the stem. If it fits tightly, the plants are ready to graft (Figure 1). We recommend using transparent Grafting clips.

8 Transparent clips allow you to see how well you match the cut surfaces of the rootstock and scion plants through the clip (Figure 2). To make graft cuts, you have options. Grafting knives B. are designed to ensure consistent cutting angles, but Figure 1. Placing a silicone Grafting clip on a stem is a good way to determine when they are more expensive than common razor blades. A a plant is ready to graft. A. The mm Grafting clip is loose, so this plant is too small to graft. B. This mm clip is snug, so the plants are ready to graft. half-size double-edge razor blade works well for Tomato Grafting , and its low cost allows you to replace them after a few grafts, which prevents potential contamina- tion if pathogens are present on the graft tool. If you use a Grafting knife, it is very important to sanitize it fre- quently.

9 How to Splice Graft The most common Grafting method for Tomato is splice Grafting . Step 1: Cut the Rootstock Stem With splice Grafting , the first step is to cut the rootstock at the stem at a deep angle (Figure 3A). The deep angle creates more surface area on the cut than a flat cut would, which allows more cells from the cut surfaces of rootstocks and scions to fuse together (an essential step in graft healing). You can cut the rootstock either above or below the cotyledons. The advantage of cutting above the cotyle- dons is that you will have more space between the graft union and soil, which means grafted plants are less Figure 2. Transparent Grafting clips allow you to see if the cut surfaces of the likely to develop adventitious roots from the scion. rootstock and scion match the surfaces in this graft do not match, which could lead to graft failure.

10 3. Vegetable Grafting However, cutting the rootstock above the cotyledons can create the problem of rootstock regrowth (that is, rootstock suckers). If you cut the rootstock below the cotyledons, it com- pletely eliminates the sucker problem because that completely removes the rootstock's meristem tissue. It is critical however, to pay close attention during trans- A. planting to ensure that the Grafting union stays above the soil (Figure 4). Step 2: Place a Grafting Clip on the Rootstock Second, after you cut the rootstock place a Grafting clip halfway over the cut stem (Figures 3B and 3C). It is important to orient the Grafting clip along the side of the graft cut so that it holds the graft union securely B. (Figure 3C). Step 3: Cut the Scion Stem Next, cut the scion stem at the same angle as the root- stock (Figure 3D).