Articles
Yield improvement in ‘Nadorcott’ mandarin using uniconazole-p and gibberellic acid
Article number
1448_49
Pages
387 – 394
Language
English
Abstract
‘Nadorcott’ mandarin (C. reticulata) has a vigorous growth habit, which could negatively impact fruit set under some growing conditions in South Africa.
Effective manipulations to control vegetative shoot growth could improve fruit set.
The objectives of this study were to evaluate the effects of different dosage rates of soil-drenched treatments of uniconazole-p (Sunny® 50 SC, Philagro SA, Somerset West, South Africa) a gibberellin (GA) biosynthesis inhibitor, alone or in combination with a foliar gibberellic acid (GA3) (ProGibb®40 SG, Philagro SA, Somerset West, South Africa) treatment, on vegetative shoot growth of the spring flush, fruit set %, and fruit yield, as well as leaf carbohydrate concentration in ‘Nadorcott’ mandarin, before and during flowering.
Experiments were conducted on full-bearing ‘Nadorcott’ mandarin trees in 2016/17, 2017/18 and 2018/19 in South Africa and were set up as randomised complete block designs with eight single-tree replicates per treatment (n=8). The study is of particular interest because obligate parthenocarpic Citrus species such as ‘Nadorcott’ mandarin could be sensitive to reduced natural GA synthesis because of triazole applications and because obligate parthenocarpic citrus cultivars could be insensitive to exogenous GA3 treatments.
A soil drench treatment of uniconazole-p applied before the emergence of the spring vegetative shoot flush reduced vegetative vigour, increased leaf carbohydrate concentration, and improved fruit yield in ‘Nadorcott’ mandarin.
A treatment dosage rate of 2 L ha‑1 was most effective and consistent throughout all the trials, whereas rates of 1 and 4 L ha‑1 were mostly inconsistent and ineffective, respectively.
The earlier timing of the application in July was more effective compared to a later timing in September.
When GA3 was applied at 100% petal drop in a combination treatment with a 2-L uniconazole-p ha‑1 soil drench applied in July, the treatment resulted in higher fruit yield compared to 2 L uniconazole-p ha‑1 applied alone and higher fruit yield compared to the untreated control.
Effective manipulations to control vegetative shoot growth could improve fruit set.
The objectives of this study were to evaluate the effects of different dosage rates of soil-drenched treatments of uniconazole-p (Sunny® 50 SC, Philagro SA, Somerset West, South Africa) a gibberellin (GA) biosynthesis inhibitor, alone or in combination with a foliar gibberellic acid (GA3) (ProGibb®40 SG, Philagro SA, Somerset West, South Africa) treatment, on vegetative shoot growth of the spring flush, fruit set %, and fruit yield, as well as leaf carbohydrate concentration in ‘Nadorcott’ mandarin, before and during flowering.
Experiments were conducted on full-bearing ‘Nadorcott’ mandarin trees in 2016/17, 2017/18 and 2018/19 in South Africa and were set up as randomised complete block designs with eight single-tree replicates per treatment (n=8). The study is of particular interest because obligate parthenocarpic Citrus species such as ‘Nadorcott’ mandarin could be sensitive to reduced natural GA synthesis because of triazole applications and because obligate parthenocarpic citrus cultivars could be insensitive to exogenous GA3 treatments.
A soil drench treatment of uniconazole-p applied before the emergence of the spring vegetative shoot flush reduced vegetative vigour, increased leaf carbohydrate concentration, and improved fruit yield in ‘Nadorcott’ mandarin.
A treatment dosage rate of 2 L ha‑1 was most effective and consistent throughout all the trials, whereas rates of 1 and 4 L ha‑1 were mostly inconsistent and ineffective, respectively.
The earlier timing of the application in July was more effective compared to a later timing in September.
When GA3 was applied at 100% petal drop in a combination treatment with a 2-L uniconazole-p ha‑1 soil drench applied in July, the treatment resulted in higher fruit yield compared to 2 L uniconazole-p ha‑1 applied alone and higher fruit yield compared to the untreated control.
Publication
Authors
O.P.J. Stander, P.J.R. Cronje
Keywords
citrus, fruit set, leaf mineral nutrition, non-structural carbohydrate
Groups involved
Online Articles (103)