Effects of ethephon and potassium nitrate on off-season flower induction in mango
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Date
2014Author
Maloba, S.
Ambuko, J.
Hutchinson, M.
Owino, W.O.
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Mango (Mangifera indica) fruit production in Kenya is seasonal with peak and off seasons
– one of the contributing factors to postharvest losses. Off-season flower induction is a
strategy that can be used to address mango seasonality. Manipulation of mango trees to
produce an off-season crop can be achieved through application of flower induction
chemicals. In the present study, the two flower induction chemicals, potassium nitrate (KNO3
)
and ethephon were evaluated on two mango varieties: ‘Apple’ and ‘Ngowe’. The study
was conducted in two agro-ecological zones (AEZs) of Kenya namely, Embu County (a
high potential AEZ) and Makueni County (a low potential AEZ). The age of the trees used
in the experiment were of similar size and vigor with an average age of 6 to 8 years.
Potassium nitrate was applied at two concentrations (2 and 4%), while ethephon was applied
at three concentrations (300, 600 and 1000ppm) and compared to a control (water). Prior to
spraying, 100 terminal shoots were marked randomly on each tree for percentage flowering
determination. After inflorescence development, 20 panicles per tree were marked randomly
on each tree to monitor fruit set. The experiment was laid out in a randomized complete
block design with three replicates and three trees per treatment. Effect of the treatments
was established from reproductive growth parameters including days to flowering and fruit
set, number of panicles per tree and average fruit set per 20 panicles. Potassium (4%)
increased percentage flowering (% of tagged shoots) in both ‘Ngowe’ and ‘Apple’ in both
AEZs. In Embu, 4% KNO3
resulted in 46% flowering in ‘Ngowe’ compared to 4% in
‘Apple’. On the contrary, in Makueni, the response was greater in ‘Apple’ (60%) compared
to ‘Ngowe’ (27%). Response to ethephon increased with concentration with the 1000 ppm
giving the best response; 22 and 28% flowering (% of tagged shoots) for Embu and Makueni,
respectively, in ‘Ngowe’. In both AEZs and varieties, flowering was d” 3% in untreated
controls. Time to flowering was significantly shortened by both KNO3
and ethephon treatments
with ‘Ngowe’ being more responsive than ‘Apple’. Significant treatment effect (pd” 0.05)
was observed on fruit set with 4% KNO3
and 1000 ppm ethephon resulting in the highest
fruit set in both AEZs and varieties. The findings reveal the potential of KNO3 and ethephon
to induce off-season flowering in ‘Apple’ and ‘Ngowe’. Further studies are on course to
optimize the treatments for commercial application.
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