Additional Amphivasal Bundles in Pedicel Pith Exacerbate Central Fruit Dominance and Induce Self-Thinning of Lateral Fruitlets in Apple    

Abstract

Apple (Malus 3 domestica) trees naturally produce an excess of fruitlets that negatively affect the commercial value of fruits brought to maturity and impact their capacity to develop flower buds the following season. Therefore, chemical thinning has become an important cultural practice, allowing the selective removal of unwanted fruitlets. As the public pressure to limit the use of chemical agents increases, the control of thinning becomes a major issue. Here, we characterized the self-thinning capacity of an apple hybrid genotype from the tree scale to the molecular level. Additional amphivasal vascular bundles were identified in the pith of pedicels supporting the fruitlets with the lowest abscission potential (central fruitlet), indicating that these bundles might have a role in the acquisition of dominance over lateral fruitlets. Sugar content analysis revealed that central fruitlets were better supplied in sorbitol than lateral fruitlets. Transcriptomic profiles allowed us to identify genes potentially involved in the overproduction of vascular tissues in central pedicels. In addition, histological and transcriptomic data permitted a detailed characterization of abscission zone development and the identification of key genes involved in this process. Our data confirm the major role of ethylene, auxin, and cell wall-remodeling enzymes in abscission zone formation. The shedding process in this hybrid appears to be triggered by a naturally exacerbated dominance of central fruitlets over lateral ones, brought about by an increased supply of sugars, possibly through additional amphivasal vascular bundles. The characterization of this genotype opens new perspectives for the selection of elite apple cultivars.

It’s great to be the King: Apple fruit development affected by the position in the cluster

“…The great number of shedded apple fruitlets has been reported by many authors and some studies have been conducted in attempt to determine an uniform and definite abscission pattern (Bangerth, 2000;Celton et al, 2014), but the clear and unequivocal answer, which fruitlets are predisposed to abscission remains unknown.…”

Different flowering response to various fruit loads in apple cultivars correlates with degree of transcript reaccumulation of a TFL1‐encoding gene

“…An apple inflorescence contains four to six flowers; the number of fruitlets reaching maturity within an inflorescence depends, among other things, on pollination and genotype (Eccher et al ., ; Celton et al ., ). Fruit of important cultivars develops mostly on inflorescences formed on spurs (Butler, ; Forshey and Elfving, ).…”

Chemical Defoliant Promotes Leaf Abscission by Altering ROS Metabolism and Photosynthetic Efficiency in Gossypium hirsutum

“…Consequently, a hypothesis involving possible cross-talk between ROS metabolism and photosynthesis jointly regulating cotton leaf abscission is proposed. Our findings not only provide important insights into leaf shedding-associated changes induced by TDZ in cotton, but also highlight the possibility that the ROS and photosynthesis may play a critical role in the organ shedding process in other crops.Previous studies have found that ethylene accelerates organ abscission, while auxin inhibits this process [5][6][7][8][9]. Meanwhile, researchers have paid attention to the fact that multiple cell wall-degrading enzymes are activated to dissolve the cell wall and middle lamella of abscission zone, including cellulases, pecticlyases, polygalactosidases [10][11][12].…”

“…Previous studies have found that ethylene accelerates organ abscission, while auxin inhibits this process [5][6][7][8][9]. Meanwhile, researchers have paid attention to the fact that multiple cell wall-degrading enzymes are activated to dissolve the cell wall and middle lamella of abscission zone, including cellulases, pecticlyases, polygalactosidases [10][11][12].…”