Benzyladenine and carbaryl effects on fruit thinning and the enhancement of return flowering of three apple cultivars

McArtney, Steven J.; Tustin, D.S.; Seymour, S.; Cashmore, W.; Looney, Norman E.

doi:10.1080/14620316.1995.11515299

Cited by 14 publications

(5 citation statements)

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“…In contrast, postbloom carbaryl treatment improved return flowering in all experiments. This is consistent with earlier reports (Batjer and Westwood, 1960;Looney et al, 1997;McArtney et al, 1995;Williams, 1993). As a thinner, carbaryl reduced both the number of fruiting sites and the number of fruit per cluster.…”

Section: Discussionsupporting

confidence: 93%

“…As a thinner, carbaryl reduced both the number of fruiting sites and the number of fruit per cluster. Since it has been reported that spurs that support two fruit until about 2 months after flowering are substantially less likely to flower than totally defruited spurs (Looney et al, 1997;McArtney et al, 1995), the carbaryl effect on thinning likely explains the return flowering benefit. However, other effects of carbaryl such as increased leaf size and specific leaf weight (Looney, 2000) may also contribute to this return flowering effect.…”

Section: Discussionmentioning

confidence: 99%

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Thinning `Fuji' Apple Blossoms with Synthetic Auxins (MCPB-ethyl or NAA) and Ethephon with or without Postbloom Thinning with Carbaryl

Guak¹,

Beulah²,

Looney³

et al. 2002

jashs

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Three experiments were conducted at two locations, two at Summerland, British Columbia, Canada and one at Corvallis, Ore., to evaluate synthetic auxins (MCPB-ethyl or NAA) and ethephon as blossom thinners for `Fuji' apple [Malus sylvestris (L.) Mill var. domestica (Borkh.) Mansf.]. These experiments also involved application of carbaryl at 1000 mg·L-1 in the postbloom period. All blossom thinners were sprayed at 85% full bloom while carbaryl was applied at 11-mm fruit diameter. Within these experiments, MCPB-ethyl at up to 20 mg·L-1 or NAA at up to 21 mg·L-1 increased whole flower cluster removal linearly with rate; however, with the Corvallis experiment MCPB-ethyl failed to result in any thinning. Neither auxin treatment consistently reduced fruit set on the remaining clusters, resulting in “clustering”. Bloom-time application of ethephon at 100 mg·L-1 with NAA further reduced crop load. Carbaryl reduced total crop load by increasing both whole cluster removal and number of sites with a single fruit. Return flowering was not improved by the auxin treatments except where there was very excessive crop reduction. Ethephon or carbaryl promoted return flowering with the carbaryl effect being more pronounced. However, this carbaryl effect was significantly countered by the bloom-time auxin whereas ethephon overcame the negative effects of the auxin treatments. The combined use of ethephon and carbaryl was effective in terms of both crop reduction and return flowering benefits. Chemical names used: 1-naphthyl N-methylcarbamate (carbaryl); 2-chloroethylphosphonic acid (ethephon); ethyl 4-(4-chloro-2-methylphenoxy) butanoate (MCPB-ethyl); and 2-(1-naphthyl) acetic acid (NAA).

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Section: Discussionsupporting

confidence: 93%

Section: Discussionmentioning

confidence: 99%

Thinning `Fuji' Apple Blossoms with Synthetic Auxins (MCPB-ethyl or NAA) and Ethephon with or without Postbloom Thinning with Carbaryl

Guak¹,

Beulah²,

Looney³

et al. 2002

jashs

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“…This lack of knowledge has limited the development of more efficient methods to control flowering in apple, and the breeding of new cultivars with more desirable flowering traits [44–46]. It has been hypothesized that the effect of GAs in apple may be mediated through inhibiting activity of cytokinins (CK), which have been shown to promote floral initiation [47, 48], but the molecular relationship between GA and CK in apple has not been well studied. Underlying this deficit in knowledge is the lack of fundamental information about GA-responsive gene expression in apple and other woody perennial plants.…”

Section: Introductionmentioning

confidence: 99%

Genetic mechanisms in the repression of flowering by gibberellins in apple (Malus x domestica Borkh.)

2019

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Background Gibberellins (GAs) can have profound effects on growth and development in higher plants. In contrast to their flowering-promotive role in many well-studied plants, GAs can repress flowering in woody perennial plants such as apple (Malus x domestica Borkh.). Although this effect of GA on flowering is intriguing and has commercial importance, the genetic mechanisms linking GA perception with flowering have not been well described. Results Application of a mixture of bioactive GAs repressed flower formation without significant effect on node number or shoot elongation. Using Illumina-based transcriptional sequence data and a newly available, high-quality apple genome sequence, we generated transcript models for genes expressed in the shoot apex, and estimated their transcriptional response to GA. GA treatment resulted in downregulation of a diversity of genes participating in GA biosynthesis, and strong upregulation of the GA catabolic GA2 OXIDASE genes, consistent with GA feedback and feedforward regulation, respectively. We also observed strong downregulation of numerous genes encoding potential GA transporters and receptors. Additional GA-responsive genes included potential components of cytokinin (CK), abscisic acid (ABA), brassinosteroid, and auxin signaling pathways. Finally, we observed rapid and strong upregulation of both of two copies of a gene previously observed to inhibit flowering in apple, MdTFL1 (TERMINAL FLOWER 1). Conclusion The rapid and robust upregulation of genes associated with GA catabolism in response to exogenous GA, combined with the decreased expression of GA biosynthetic genes, highlights GA feedforward and feedback regulation in the apple shoot apex. The finding that genes with potential roles in GA metabolism, transport and signaling are responsive to GA suggests GA homeostasis may be mediated at multiple levels in these tissues. The observation that TFL1-like genes are induced quickly in response to GA suggests they may be directly targeted by GA-responsive transcription factors, and offers a potential explanation for the flowering-inhibitory effects of GA in apple. These results provide a context for investigating factors that may transduce the GA signal in apple, and contribute to a preliminary genetic framework for the repression of flowering by GAs in a woody perennial plant.

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“…Thinning decisions are considered to be among the most important since they directly impact yield, fruit quality, profitability, and growing habit. Post-bloom chemical fruit thinning using plant growth regulators and carbamate insecticides are the main thinning methods to reduce crop load in apple orchards [6][7][8]. However, there are numerous external factors such as weather conditions that greatly impact the efficacy of post-bloom fruit thinning spray applications [6,9,10].…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Blossom Thinning Spray Timing Strategies in Apple

2021

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In the eastern USA and several other apple-growing regions, apple blossom thinning using lime sulfur is a relatively new crop load management strategy. This study sought to evaluate how application timing of lime sulfur + stylet oil blossom thinning sprays would influence thinning efficacy and crop safety of ‘Gala’ apples. This project occurred at two locations in the USA, Winchester, Virginia, and Mills River, North Carolina, during the 2019 growing season. Two main timing strategies were assessed: (1) model-guided sprays with the pollen tube growth model (PTGM), (2) fixed spray intervals with the first spray applied at a specified percentage of open bloom (20% vs. 80%), and the second spray applied at a reapplication interval (48 h vs. 72 h). Model-guided and 20% open bloom + 48-h treatments reduced fruit set and increased fruit weight, diameter, and length at both sites. Treatments with a delayed first spray at 80% open bloom or a more extended second reapplication of 72 h were generally ineffective. There was no conclusive evidence that lime sulfur + stylet oil blossom thinning spray timing influenced russet incidence/severity or leaf phytotoxicity. This study demonstrated that effective and safe blossom thinning can be obtained from applying two sprays at 20% open bloom and 48 h thereafter or using the PTGM.

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Benzyladenine and carbaryl effects on fruit thinning and the enhancement of return flowering of three apple cultivars

Cited by 14 publications

References 1 publication

Thinning `Fuji' Apple Blossoms with Synthetic Auxins (MCPB-ethyl or NAA) and Ethephon with or without Postbloom Thinning with Carbaryl

Thinning `Fuji' Apple Blossoms with Synthetic Auxins (MCPB-ethyl or NAA) and Ethephon with or without Postbloom Thinning with Carbaryl

Genetic mechanisms in the repression of flowering by gibberellins in apple (Malus x domestica Borkh.)

Evaluation of Blossom Thinning Spray Timing Strategies in Apple

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