A bud-sport is a mutation that occurs in plants that appears as a sudden change in the genetic traits of a branch. These "sports" may affect fruit (color, shape or maturity), tree structure, time to bloom, leaf shape or color, and many other traits.
Some of these mutations have become commercially important like - red colored fruit sports of apple, 'Ruby Red' grapefruit and many traits in ornamental plants.
This type of a bud-sport in called a witch's broom. It has shorter internodes and grafted plants from this mutation leads to dwarf conifers.