An improved shoot-tip grafting method for virus free citrus plants

Abstract

The shoot-tip grafting (denoted to STG) method developed by Navarro was improved to establish a method for further enhancing the seedling maturation rate. At first, a method for enhancing the rate of successful grafts by STG was investigated. As a result, Troyer citrange seedlings were suitable for the rootstock of STG because this rootstock had a high rate of successful grafts throughout the year. Especially, the rate of successful grafts was highest when this rootstock was used 12 days after sowing. The rate of successful grafts was improved by using a silicon plug as the cap for the vessel containing medium for growing the STG seedling. Further, the rate of successful gragts was increased by applying heat-treatment to the scion for STG. A method for enhancing the rate of successful grafts by side grafting was also investigated. As a result, seedlings of Roughlemon as a rootstock for side grafting had the highest rate of successful grafts throughout the year. The scions obtained at different growth stages of plants made virus-free by STG were used for side grafting. A high rate of successful grafts was shown when the side grafting was carried out using scions which were obtained from plants just after a successful take of STG. Botrytis sp. bud rot frequently occurred after the take of side grafting. If a method to control this disease is developed, virus-free plants can be obtained using this improved STG at the ratio of 90% or higher.