Growing vegetable plants for open-field production requires a plant that can withstand environmental challenges such as heavy rains, wind, and stressful temperatures. Obviously, the strength of the graft union is very important to the survival of the young grafted plant. Plants placed in the field as seedlings are dependent on the ability to survive the first week in the soil and establish an anchoring root system that can absorb water and nutrients. Open-field production of fresh-market tomatoes is reliant on transplants that are produced as plugs. As a result of the expense of growing these seedlings and the goal of hitting markets at prescribed times, growers contract with transplant producers to produce plants throughout the growing season. Plant losses during grafted transplant production can occur as a result of disease, environmental conditions, and mechanical damage. This process requires precise scheduling and weather can delay planting dates. Varieties are selected for horticultural characteristics that coincide with disease and market demand. Although aggressive breeding practices are being adopted to include all the desired resistance and horticultural characteristics in one package, it is a difficult task as a result of linkage drag (Scott and Gardner, 2007). In addition, the decreased use of methyl bromide has forced growers to use alternatives such as grafted plants to manage soilborne pests and pathogens.
During the process of grafting, the scion can be selected for horticultural characteristics such as fruit quality, yield, and disease resistance. Also, rootstocks can be selected for soilborne disease, nematode resistance, and root vigor, all found in open-field conditions. The term open field means plants exposed to the natural environment with no protective shelter. Growing tomatoes in the southern United States often means plants must tolerate increased wind velocity and heavy rain events that can damage young plants. Also, open-field fresh tomatoes may be grown on plastic mulch, which can raise soil temperatures that may increase plant stress. Most of the information published thus far is related to plants grown under sheltered conditions (Kubota et al., 2008; Louws et al., 2010) and focuses on the viability of the technology. Limited literature addresses the reasons for choosing one grafting technique over another. Grafted plants used in open-field production require a grafting technique that can efficiently produce large quantities of plants that can survive in exposed fields. Little is known about the effect of grafting techniques on the physical attributes of the tomato seedling and plant survival or graft union integrity (Lee et al., 2010; Oda et al., 1994). The objectives of the study are to explore the effects of graft angle on plant survivability and graft union integrity.
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