Effects of various inductive periods and chemicals on flowering and vegetative growth of Tommy!Atkins' and 'Keitt' mango (Mangifera indica) cultivars

The effects of potassium nitrate and paclobutrazol on flowering and vegetative growth of 'Tommy Atkins' and 'Keitt' mango (Mangifera indica) were studied for various periods in inductive and non-inductive temperature regimes. The experiment was done at the University of Pretoria experimental farm in a temperature-regulated cabinet on 2-year-old potted 'Tommy Atkins' and 'Keitt' mango cultivars. 'Keitt' was more sensitive towards low temperature floral induction than 'Tommy Atkins'. For both cultivars, the trend for the interaction of duration and cultivar revealed the possible floral induction complementation effect of PBZ after the trees stayed only 15 days at the inductive temperature (10/15degreesC). Paclobutrazol also significantly reduced vegetative growth and number of days required for visible inflorescence emergence in both cultivars. Potassium nitrate promoted the initiation of buds for vegetative growth in non-inductive temperature conditions and reproductive growth in inductive conditions. The minimum inductive period at 10/15degreesC (12 h light/12 h dark) required for "complete" floral induction and development was found to be 35 days for both cultivars. Surpassing the inductive (cold) period showed adverse effects on normal development of the reproductive parts and also delayed inflorescence emergence.