Variation of inflorescence character in response to GA3 application at advancing stages of terminal floral bud differentiation in mango

S.A. Oosthuyse
In each of six cultivar blocks, 2- to 3-year-old 'Sensation', 'Tommy Atkins', 'Heidi', 'Kent', 'Zill' or 'Keitt' mango trees sprayed with GA3 (100 ppm) at 14-day intervals from 20 April until 24 August. One spray was administered per tree, and the trees were sprayed to run-off. In general, spraying during the period from 18 May until 1 June forced the development of rudimentary inflorescences. Generally, for the earlier spraying dates during this period, these were short rosette-like shoot structures development of which was largely inhibited. Later spraying during this period generally gave rise to the development of rosette-like shoot structures, development of which was less inhibited, and spraying late during this period generally forced the development of extended shoot-like structures with well-developed bracts. Axillary inflorescence branch development was generally absent in these structures. In general, spraying during the period from 15 June until 4 weeks before bud-break generally forced the development of rudimentary inflorescences possessing flowering laterals and terminated by structures bearing flowers. Generally, the terminal bud and distally located axillary buds developed as structures bearing flowers in the trees sprayed earlier during this period, whereas an increasing number of axillary buds developed into such structures in trees sprayed later during this period. In general, spraying 2 weeks prior to normal bud-break, and at and after normal bud-break, gave rise to the development of “leafy inflorescences” bracts of which were less developed, or to the development of inflorescences with highly elongated main and other axes. Developing inflorescences were removed at the time of spraying when spraying took place after the time of normal bud-break. Due to this removal, inflorescence number declined and new shoot number increased per tree with date of spraying. This clearly resulted from lateral buds (not terminal buds), which were truly dormant when spraying, always developing to become new shoots. Development here occurred when conditions were less inductive. The foregoing observations clearly indicate that, when spraying trees possessing floral buds at various stages in degree of development, the effect of GA3 is to arrest continued inflorescence development and to force outgrowth of the structure present at or shortly after the time of spraying. Early spraying forced the outgrowth of rudimentary inflorescence structures. To inhibit flowering, the recommendation was made of applying GA3 after bud-break has commenced, removing all of the apical buds and inflorescences present on the terminal shoots when spraying.
Oosthuyse, S.A. (2017). Variation of inflorescence character in response to GA3 application at advancing stages of terminal floral bud differentiation in mango. Acta Hortic. 1183, 175-180
DOI: 10.17660/ActaHortic.2017.1183.24
https://doi.org/10.17660/ActaHortic.2017.1183.24
Mangifera indica, dormancy, bud-break, inhibition, forcing, abnormality
English
1183_24
175-180

Acta Horticulturae