Abstract
In grapes, caps stuck to flower clusters can become a source of infection with gray mold disease. Thus, it is generally recommended that such caps are removed. We designed a new tool to remove the caps at the 1st gibberellin treatment to induce artificial seedless grape berries when its application time is near full bloom. A round brush was attached to the upper part of the cup used for gibberellin treatment. When a flower cluster soaked with gibberellin solution passed through the brush, the caps were efficiently removed from the flowers. ‘Kyoho’ and ‘Pione’ grapes cultivated in an open field were treated with gibberellin using this tool 3 days after full bloom. The cap removal rate immediately after treatment was 46–56% in the experimental group (the cup with a brush), whereas that in the control group (cup without a brush) was 4–8%. On the second day after gibberellin treatment, the cap removal rate increased to 70–76% in the experimental group because even more caps fell off the day after treatment, whereas the rate in the control group was 38–53%. A visual comparison of the young berries and the fruit at harvest showed that use of the tool did not cause scars on the surfaces of the berries. The tool did not have any undesirable effect on fruit quality. Therefore, this new tool is a useful labor-saving method for removing caps from flowers during the 1st gibberellin treatment in ‘Kyoho’ and ‘Pione’ grapes.
