Evaluation of a potential strategy to delay 'Keitt' mango (Mangifera indica) flowering in sub-tropical latitudes.
Davenport T. L., Smith S. M.
Author Affiliation: University of Florida, Trop. Res. & Ed. Ctr., 18905 SW 280 St., Homestead, FL 33031, USA.
PGRSA Quarterly 25 : 114-129
Abstract : Experiments were conducted in Florida, USA, to delay flowering of mango cv. Keitt. Reproductive shoot initiation in resting buds was inhibited by GA3 (200 mg/litre); initiation of reproductive growth later in the season was stimulated by cool, floral-inductive temperatures and the application of chemicals with the potential to stimulate bud break. GA3 was applied to foliage during November, November + December, December, November + December + January, or December + January. Maleic hydrazide was also tested as a single November application. Several compounds were tested alone or in combination for their efficacy to stimulate bud break. Treatments consisted of foliar application of 2 or 4% hydrogen cyanamide (Dormex), 2% low-biuret urea (Unocal Plus), 4% hydrogen cyanamide + 2% low-biuret urea, 2% low-biuret urea + 10-4 M naphthylphthalamic acid (NPA) [naptalam] + 10-4 M benzyladenine (BA), 2% low-biuret urea + 10-4 M NPA + 10-4 M BA + uniconazole, and 4% NH4NO3 applied in late November. GA3 inhibited bud break when applied in December + January; inhibition was most persistent when applied during November + December + January. The only treatments stimulating rapid shoot initiation were those containing hydrogen cyanamide; 2% low-biuret urea + NPA + BA + uniconazole was marginally effective. Increased shoot initiation due to hydrogen cyanamide was offset by the occurrence of leaf necrosis and abscission resulting in vegetative rather than reproductive shoots even in floral inductive conditions. Reduction in reproductive shoot production was noted in the GA3 treatments which were most effective at inhibiting bud break, indicating that these treatments were not feasible for growers to use to extend the harvest season of mango.