APICAL SHOOT DEFOLIATION AND ITS EFFECT ON FLORAL DIFFERENTIATION OF MANGO ‘TOMMY ATKINS’

Abstract

Macroscopic and microscopic characteristics were determined, as well as the date of floral differentiation in the meristem of terminal shoots of mango (Mangifera indica L. ) ‘Tommy Atkins’, grown under rainfed conditions. A sample of 80 terminal shoots from twenty mango trees were hand defoliated every other week from September 30 September though December 31 in a 15-year-old commercial orchard in Jalcocotán, Nayarit (21° 29’ NL, 105° 04’ WL). Control shoots were not defoliated. On each date, 40 apical buds were collected and their macro and microscopic characteristics were recorded. On the first year, all shoots defoliated from September 30 to October 15 produced vegetative growth only, while on the second year 12.5 and 17 % of shoots produced inflorescences. Production of inflorescences began on shoots treated on October 31 (20.8 %). In both years, more than 85 % of apical buds from defoliated shoots were already differentiated on December 31 and the differentiated buds were classified on Stage 3. Macroscopically these buds had a conical shape and obvious separation of bud scales, and microscopically they showed an elongated primary axis, initial development of secondary axis and presence of tertiary axes in the inflorescence. The date of floral differentiation was associated with the accumulation of temperatures ≤ 20 °C.