Abstract
The aim of this work was to study the effect of fall defoliation and chemical application on the progression and release of dormancy, and phenology, of low-chill peach ‘Flordaking’ under temperate climate conditions. At the onset of leaf fall, ‘Flordaking’ peach (Prunus persica L. Batsch) trees were defoliated or treated with hydrogen cyanamide (2.5 g L-1 a.i), norflurazon (46 g L-1 a.i.) or ethephon (20 mg L-1 a.i.). Untreated trees were used as the control. The rate of budbreak and the mean time to budbreak (MTB) was tested on stem isolates in a phytotron, whereas tree phenology and vegetative and reproductive traits were evaluated in a field experiment. Defoliation and chemical treatments significantly affected the rate of budbreak evolution of floral, but not of vegetative, buds. Treatments also significantly affected the evolution of the MTB of both vegetative and floral buds, but with a greater effect on the latter. In the field, the phenology of Flordaking was more affected by treatments that modified the depth of dormancy than those which affected the percentage of budbreak in excised shoots. Defoliation and hydrogen cyanamide treatments advanced sprouting (15 and ten days, respectively) and blooming (16 and four days, respectively), whereas ethephon delayed flowering and fruit set by three days each. Fall defoliation at the beginning of leaf abscission appears to be a strong tool to manipulate the evolution of dormancy and the time of spring bloom of Flordaking, mainly when insufficient chilling accumulation is forecasted.
Highlights
In the central-eastern area of the Santa Fe province (Argentina), average chilling accumulation is around 300 hours (Gariglio et al, 2006a), with high variability between years
The aim of this work was to study the effect of fall defoliation and chemical application on the progression and release of dormancy, and phenology, of low-chill peach ‘Flordaking’ under temperate climate conditions
The rate of budbreak and the mean time to budbreak (MTB) was tested on stem isolates in a phytotron, whereas tree phenology and vegetative and reproductive traits were evaluated in a field experiment
Summary
In the central-eastern area of the Santa Fe province (Argentina), average chilling accumulation is around 300 hours (Gariglio et al, 2006a), with high variability between years. The low chill peach variety ‘Flordaking’ requires 450 chilling hours (CH), being the variety with the highest chilling requirement of those recommended for cultivation; despite the excellent adaptation of Flordaking to different regions of Argentina, we observed that it shows variable vegetative and reproductive traits between years (Gariglio et al, 2009). Flordaking was the peach variety that showed the highest sensitivity to changes in chilling accumulation between years, and so it seems to be the most appropriate variety in which to study dormancy induction, evolution and release in the central area of Argentina. Fall application of gibberellins and ethephon delayed blooming of both peach (Luna et al, 1990) and apricot trees (Ganji Moghadam and Mokhtarian, 2006)
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