Proposed physiological mechanism of mango fruitlet abscission

Hagemann, M.H.; Winterhagen, Patrick; Roemer, M.G.; Hegele, M.; Wünsche, J.

doi:10.17660/actahortic.2016.1119.10

Cited by 3 publications

(4 citation statements)

References 28 publications

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“…In the natural abscission process, it is suggested that fruitlet-derived ethylene is synthesized in the pericarp and diffuses to the AZ (Nunez-Elisea and Davenport, 1986 ; Malik et al, 2003 ) where it induces the upregulation of ethylene receptors (Stepanova and Alonso, 2009 ) prior to the induction of the abscission process. These findings lead to the hypothesis that during natural abscission, ethylene receptors are first upregulated in the fruitlet and then in the pedicel (Hagemann et al, in press ). Chemical induction of the abscission by ethephon would result in a simultaneous upregulation of ethylene receptors in fruitlets and pedicels (Figure 3 ).…”

Section: Discussionmentioning

confidence: 98%

“…Irrespective of the treatment applied, low FDF values were symptomatic for fruitlets breaking at the abscission zone (Hagemann et al, 2015 , in press ) and are indicative of an advanced abscission process. Developmental disorders or nutritional stress during embryogenesis, leading to seed degeneration, was previously suggested as another symptomatic cause of fruitlet abscission (Singh, 1961 ; Botton et al, 2011 ).…”

Section: Discussionmentioning

confidence: 99%

“…In conclusion, the data suggest that the ethephon-induced fruitlet abscission follows a different sequence of events (Figure 6 ) compared to the natural abscission process. In the latter case, resource deficiency, e.g., carbohydrate supply limitations for fruitlet growth, or seed degeneration with auxin signaling disruption are primary physiological causes (Xie et al, 2013 ; Hagemann et al, in press ). In contrast, the ethephon-induced fruitlet abscission process responds initially with a reduction of the PAT capacity in the pedicel, followed by an upregulation of ethylene receptors and then a decline in sucrose concentration; physiological markers that were not linked to seed degeneration.…”

Section: Discussionmentioning

confidence: 99%

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Ethephon induced abscission in mango: physiological fruitlet responses

et al. 2015

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Fruitlet abscission of mango is typically very severe, causing considerable production losses worldwide. Consequently, a detailed physiological and molecular characterization of fruitlet abscission in mango is required to describe the onset and time-dependent course of this process. To identify the underlying key mechanisms of abscission, ethephon, an ethylene releasing substance, was applied at two concentrations (600 and 7200 ppm) during the midseason drop stage of mango. The abscission process is triggered by ethylene diffusing to the abscission zone where it binds to specific receptors and thereby activating several key physiological responses at the cellular level. The treatments reduced significantly the capacity of polar auxin transport through the pedicel at 1 day after treatment and thereafter when compared to untreated pedicels. The transcript levels of the ethylene receptor genes MiETR1 and MiERS1 were significantly upregulated in the pedicel and pericarp at 1, 2, and 3 days after the ethephon application with 7200 ppm, except for MiETR1 in the pedicel, when compared to untreated fruitlet. In contrast, ethephon applications with 600 ppm did not affect expression levels of MiETR1 in the pedicel and of MiERS1 in the pericarp; however, MiETR1 in the pericarp at day 2 and MiERS1 in the pedicel at days 2 and 3 were significantly upregulated over the controls. Moreover, two novel short versions of the MiERS1 were identified and detected more often in the pedicel of treated than untreated fruitlets at all sampling times. Sucrose concentration in the fruitlet pericarp was significantly reduced to the control at 2 days after both ethephon treatments. In conclusion, it is postulated that the ethephon-induced abscission process commences with a reduction of the polar auxin transport capacity in the pedicel, followed by an upregulation of ethylene receptors and finally a decrease of the sucrose concentration in the fruitlets.

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Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Ethephon induced abscission in mango: physiological fruitlet responses

et al. 2015

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“…During fruit development, carbohydrates are not only used directly as carbon nutrients but also function as signals in regulating fruit drop [7][8][9]. Studies on citrus [10,11], longan [12], and mango [13] showed that fruit shedding is triggered when the sugar content decreases below the critical threshold required for fruit growth. Many experiments on the fruit abscission induced by starvation stress, such as tree shading [14][15][16], defoliation [17], and girdling plus defoliation [18,19], revealed that the decreased glucose, fructose, and sucrose contents in fruit were associated closely with fruit drop.…”

Section: Introductionmentioning

confidence: 99%

Changes of Fruit Abscission and Carbohydrates, Hormones, Related Gene Expression in the Fruit and Pedicel of Macadamia under Starvation Stress

Yang

Xiang

2022

Horticulturae

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In order toexplore the regulation mechanism of macadamia fruitlet abscission induced by ‘starvation stress’, a treatment of girdling and defoliation was applied to the bearing shoots of macadamia cultivar ‘H2’ at the early stage of fruit development, simulating the starvation stress induced by interrupting carbon supply to fruit. The levels of carbohydrates, hormones, and related gene expression in the different tissues (husk, seed, and pedicel) were investigated after treatment. The results showed that a severe fruit drop occurred 3~5 d after starvation stress treatment. The contents of glucose, fructose, and sucrose in both the husk and the seed were significantly decreased, as well as the fructose and sucrose in the pedicel; this large reduction occurred prior to the massive fruit shedding. Starvation stress significantly reduced the GA3 and ZR contents and enhanced the ABA level in the pedicel and the seed, whereas it did not obviously change these hormones in the husk. After treatment, IAA content decreased considerably in both the husk and seed but increased remarkably in the pedicel. In the husk, the expression of genes related to sugar metabolism and signaling (NI, HXK2, TPS, and TPP), as well as the biosynthesis of ethylene (ACO2 and ACS) and ABA (NCED1.1 and AAO3), was significantly upregulated by starvation stress, as well as the stress-responsive transcription factors (AP2/ERF, HD-ZIP12, bZIP124, and ABI5), whereas the BG gene associated with ABA accumulation and the early auxin-responsive genes (Aux/IAA22 and GH3.9) were considerably suppressed during the period of massive fruit abscission. Similar changes in the expression of all genes occurred in the pedicel, except for NI and AP2/ERF, the expression of which was significantly upregulated during the early stage of fruit shedding and downregulated during the period of severe fruit drop. These results suggest that complicated crosstalk among the sugar, IAA, and ABA signaling may be related to macadamia fruitlet abscission induced by carbohydrate starvation.

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