Sucker Control of Tomato Seedlings by Fatty Alcohol Application

Vegetable Grafting offers an alternative technology to fumigants to manage soil-borne diseases under open-field conditions. Given that grafted seedlings are transplanted by machines, the position of the graft union has to be high to prevent the vulnerable scion from contacting the soil. For tomato, while grafting above the rootstock cotyledons could be a solution to assure adequate distance between grafted union and soil line, potential grow-out of rootstock axillary shoots (suckers) can be problematic because of high labor cost to manually prune suckers. Fatty alcohol has been used to control sucker growth after decapitation in tobacco production and recently demonstrated as part of a grafting technique applied for cucurbit rootstocks. It is found that fatty alcohol kills only rapidly-dividing meristematic tissue in tobacco. In this study, we examined the possible use of fatty alcohol for sucker control of tomato seedlings (Solanum lycopersicum cv. ‘Roma VF’). We applied various concentrations (0, 5, 7.5, 10, 12.5, 15, 20, or 30 %) of commercially available fatty alcohol to the axillary meristematic region of three true-leaf stage tomato seedlings grown inside a greenhouse. Suckers were forced to develop by pinching the seedlings. We evaluated incidence of visible axillary bud/sucker development and degree of damage on seedlings on days 1, 7, 14, and 21 after pinching. Sucker incidence decreased with increasing concentration of fatty alcohol. The sucker incidence also increased over time except for at 0%. After 14 days of pinching, application of fatty alcohol at 15% or higher concentration significantly suppressed the percent sucker incidence below 10%. Twenty-one days after pinching, the sucker incidence was further increased in all concentrations, and the sucker incidence exceeded 10% except at the highest concentration of 30%. Damage on seedlings was mainly observed for cotyledons. The percent damage increased with increasing concentration of fatty alcohol, resulting in more than 10% damage at 12.5% or higher concentrations. Under a stereomicroscope, we observed that axillary meristems contacted by fatty alcohol turned brown and withered. This study showed that fatty alcohol effectively killed axillary meristems of tomato and might be a useful chemical tool to control sucker growth from tomato rootstocks. Further studies are currently underway to evaluate the influence of fatty alcohol application on grafting success as well as recurring rootstock adventitious shoot growth.