DELAYED INFLORESCENCE BUD INITIATION, A CLUE FOR THE LACK OF RESPONSE OF THE ‘TOMMY ATKINS’ MANGO TO PROMOTERS OF FLOWERING

November and December foliar sprays of ammonium nitrate (NH₄NO₃) have been successful to promote early flowering of several mango cultivars in Nayarit, Mexico, but they have been unsuccessful in promoting early flowering of the cultivar Tommy Atkins. This study was conducted to assess the effect of three chemical flowering promoters on the time of inflorescence initiation in apical buds of the ‘Tommy Atkins’ mango. Foliar sprays of NH₄NO₃ (2%) were applied three times (at biweekly intervals) in November or December. Ethrel (0, 200, 500, 1000 ppm and 200 ppm + urea 1%) was sprayed twice in November. A single soil application of paclobutrazol (PBZ) at 0, 10 or 20 g/tree was done in July. Flower anthesis was 28 to 35 days earlier in PBZ-treated trees than in non-treated controls. PBZ suppressed vegetative flushing during summer and fall, allowing shoots to mature and initiate apical inflorescences earlier than shoots of the control trees, which had flushed during fall. NH₄NO₃ or ethrel were ineffective in stimulating early flowering of ‘Tommy Atkins’ trees in this study. The lack of response to NH₄NO₃ or ethrel was attributed to the presence of immature shoots (due to their untimely flushing in the fall) at the time of treatment application.