Ethephon induced abscission in mango: physiological fruitlet responses

Abstract

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.

Genome-wide identification and expression analysis of citrus fruitlet abscission-related polygalacturonase genes

“…Exogenous application of aminoethoxyvinyl-glycine (AVG), an inhibitor of ethylene biosynthesis, obviously decreases citrus fruitlet abscission (CFA); on the contrary, 1-aminocyclo-propane-1-carboxylic acid (ACC), an ethylene precursor, effectively promotes CFA (Gómez-Cadenas et al 2000;Iglesias et al 2006). Similar results have also been reported in other fruit crops including apple (Stopar et al 2007), mango (Hagemann et al 2015), tomato (Zhang et al 2015) and litchi (Li et al 2015), plum (Meland and Kaiser 2016), etc. Compared to ethylene, auxin has opposite effect on CFA (Xie et al 2015a, b).…”

Disruption of the Auxin Gradient in the Abscission Zone Area Evokes Asymmetrical Changes Leading to Flower Separation in Yellow Lupine

“…The basipetal auxin movement prevents organ detachment, whereas its decay increases the sensitivity of the AZ to ET [1,48]. On the other hand, the abscission model proposed for mango fruits assumed that ET inhibits PAT, then the expression of ET receptor genes (MiETR1 and MiERS1) is enhanced, and consequently, the sugar content in fruit decreases, and hence the abscission is stimulated [49]. It should also be emphasized that auxin can stimulate ET production, and in this way, causes organ separation [50][51][52].…”

Synthesis and structure-activity relationships of new pyrazole derivatives that induce triple response in <i>Arabidopsis</i> seedlings

“…Currently, the prodrug of ethylene, ethephon, which degrades and subsequently releases ethylene in plant tissues, is used in a major way to manipulate the ethylene levels in plant tissues. 14) Ethephon has been used for promoting fruit ripening 15) and abscission 16,17) and for weed control. 18) Ethephon has also been registered as a pesticide for a number of food, feed, and nonfood crops such as cotton.…”