Abstract
Irregular fruit production across successive years is a major issue that limits the profitability of most temperate and tropical fruit crops. It is particularly affected by the reciprocal relationships between vegetative and reproductive growth. The concept of the costs of reproduction is defined in terms of losses in the potential future reproductive success caused by current investment in reproduction. This concept, developed in ecology and evolutionary biology, could provide a methodological framework to analyze irregular bearing in fruit crops, especially in relation to the spatial scale at which studies are done. The objective of this study was to investigate the direct effects of reproduction during a growing cycle on reproduction during the following growing cycle and the indirect effects through vegetative growth between these two reproductive events, for four mango cultivars and during two growing cycles. Two spatial scales were considered: the growth unit (GU) and the scaffold branch. Costs of reproduction were detected between two successive reproductive events and between reproduction and vegetative growth. These costs were scale-dependent, generally detected at the GU scale and infrequently at the scaffold branch scale, suggesting partial branch autonomy with respect to processes underlying the effects of reproduction on vegetative growth. In contrast, the relationships between vegetative growth and reproduction were positive at the GU scale and at the scaffold branch scale in most cases, suggesting branch autonomy for the processes, mainly local, underlying flowering and fruiting. The negative effect of reproduction on vegetative growth prevailed over the positive effect of vegetative growth on the subsequent reproduction. The costs of reproduction were also cultivar-dependent. Those revealed at the GU scale were related to the bearing behavior of each cultivar. Our results put forward the crucial role of vegetative growth occurring between two reproductive events. They are discussed in the context of irregular bearing considering both the spatial scale and the various bearing habits of the mango cultivars, in order to formulate new hypotheses about this issue.
Highlights
Fruit production in most tropical and temperate perennial fruit crops is irregular across successive years
Cultivars differ in their bearing behavior (Monselise and Goldschmidt, 1982; Knight et al, 2009), and recent studies evidenced the genetic control of irregular bearing in apple (Guitton et al, 2012; Durand et al, 2013)
We chose to study four of these cultivars with contrasted patterns of irregular bearing in the orchard: José, a local cultivar from Reunion Island characterized by a strong irregular bearing; Cogshall, a Floridian cultivar that is extensively grown in Reunion Island and which is characterized by a weak irregular bearing; Kensington Pride, the main cultivar grown in Australia with a quite regular productivity in Reunion Island; and Irwin, a Floridian cultivar, the most regular bearer among the four cultivars studied
Summary
Fruit production in most tropical and temperate perennial fruit crops is irregular across successive years. Irregular bearing is characterized by years of high fruit production (‘on’ years) and by years of low fruit production (‘off ’ years) (Monselise and Goldschmidt, 1982). Deciphering the Costs of Reproduction in Mango traits are related to yield, irregular bearing affects fruit quality across years and has economic consequences for the fruit industry. Several studies suggest that irregular bearing is related to the balance between various types of resources (e.g., carbon/nitrogen ratio) and to hormonal factors (auxin, cytokinins, gibberellins) at the scales of the whole tree and of the shoot (Chan and Cain, 1967; Marino and Greene, 1981; Goldschmidt and Golomb, 1982; Rosecrance et al, 1998). Cultivars differ in their bearing behavior (Monselise and Goldschmidt, 1982; Knight et al, 2009), and recent studies evidenced the genetic control of irregular bearing in apple (Guitton et al, 2012; Durand et al, 2013)
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