Cotyledonary axillary shoot control by fatty alcohol application for grafting tomato

In tomato (Solanum lycopersicum), grafting position is recommended to be below rootstock cotyledons to avoid undesirable axillary shoots growing out from the cotyledons. In contrast, grafting above the rootstock cotyledons is desired to assure adequate distance between grafted union and soil line, only if there is no potential grow-out of axillary shoots from rootstock cotyledons. The objective of this preliminary study was to examine fatty alcohol application on cotyledonary axils of tomato seedlings to control undesirable axillary shoot extension from rootstock in tomato grafting. Solution containing various concentrations of a commercial fatty alcohol compound was applied to different growing stages of cotyledonary axillary shoots (nonextended buds or extended shoots) of tomato seedlings grown in a greenhouse. When fatty alcohol was applied directly to cotyledonary axillary buds, the seedlings were then pinched to force-induce the axillary shoot extension to assure the efficacy of the fatty alcohol treatment. High concentrations (10% and 15%) of fatty alcohol suppressed incidence of axillary shoot extension to less than 7% by killing buds. However, when applied to extended axillary shoots, application with 2% or higher concentrations of fatty alcohol caused plant collapse because excess fatty alcohol flowed down the stem and presumably damaged the root system. Therefore, we concluded that application of fatty alcohol to control cotyledonary axillary shoots of tomato rootstock could be possible only if fatty alcohol at effective concentration (10% to 15%) is applied exclusively to the target buds.