Warm temperature during floral bud transition turns off EjTFL1 gene expression and promotes flowering in Loquat (Eriobotrya japonica Lindl.).

The Rosaceae family includes several deciduous woody species whose flower development extends over two consecutive growing seasons with a winter dormant period in between. Loquat (Eriobotrya japonica Lindl.) belongs to this family, but it is an evergreen species whose flower bud initiation and flowering occur within the same growing year.

Reversion of fruit-dependent inhibition of flowering in Citrus requires sprouting of buds with epigenetically silenced CcMADS19.

In Citrus, the response to environmental floral inductive signals is inhibited by the presence of developing fruits. The mechanism involves epigenetic activation of the CcMADS19 locus (FLC orthologue), encoding a floral repressor. To understand how this epigenetic regulation is reverted to allow flowering in the following season, we have forced precocious sprouting of axillary buds in fruit-bearing shoots, and examined the competence to floral inductive signals of old and new leaves derived from them.

Fruit-dependent epigenetic regulation of flowering in Citrus.

In many perennial plants, seasonal flowering is primarily controlled by environmental conditions, but in certain polycarpic plants, environmental signals are locally gated by the presence of developing fruits initiated in the previous season through an unknown mechanism. Polycarpy is defined as the ability of plants to undergo several rounds of reproduction during their lifetime, alternating vegetative and reproductive meristems in the same individual. To understand how fruits regulate flowering in polycarpic plants, we focused on alternate bearing in Citrus trees that had been experimentally established as fully flowering or nonflowering.

Bud sprouting and floral induction and expression of FT in loquat [Eriobotrya japonica (Thunb.) Lindl.].

EjFT1 and EjFT2 genes were isolated and sequenced from leaves of loquat. EjFT1 is involved in bud sprouting and leaf development, and EjFT2 in floral bud induction. Loquat [Eriobotrya japonica (Thunb.

Gibberellin reactivates and maintains ovary-wall cell division causing fruit set in parthenocarpic Citrus species.

Citrus is a wide genus in which most of the cultivated species and cultivars are natural parthenocarpic mutants or hybrids (i.e. orange, mandarin, tangerine, grapefruit).

Loquat fruit ripening is associated with root depletion. Nutritional and hormonal control.

In woody species, it is known that there is a competition for nutrients, water and carbohydrates between root and fruit-shoot systems, however the influence of root development on fruit quality has received little attention. This research aims to identify the network of mechanisms involved in loquat (Eriobotrya japonica Lindl.) fruit ripening in connection with root activity.

Carbon utilization by fruit limits shoot growth in alternate-bearing citrus trees.

Fruit load in alternate-bearing citrus trees is reported to alter shoot number and growth during spring, summer, and autumn flushes, and the source-sink balance, which affects the storage and mobilization of reserve nutrients. The aim of this work was to assess the extent of shoot growth inhibition resulting from the presence of fruits in 'Moncada' mandarin trees loaded with fruit (ON) or with very light fruit load (OFF), and to identify the role of carbohydrates and nitrogenous compounds in the competition between fruits and shoots. Growth of reproductive and vegetative organs was measured on a monthly basis.

Cell division interference in newly fertilized ovules induces stenospermocarpy in cross-pollinated citrus fruit.

Seedlessness is a highly desirable characteristic in fresh fruits. However, post-fertilization seed abortion of cross-pollinated citrus fruit is uncommon. The factors regulating stenospermocarpy in citrus are unknown.

Proteomic study of 'Moncada' mandarin buds from on- versus off-crop trees.

A proteomic analysis of buds from mandarin trees with contrasting fruit load (on- and off-crop trees) was carried out during the onset of low-temperature induction. The aim of the study was to find out more about the molecular mechanism relating to alternate bearing in Citrus and its relationship with flowering. The 'Moncada' variety (Clementine 'Oroval'x'Kara' mandarin), displaying remarkable behaviour in alternate production, was used in this study.

Use or abuse of bioinformatic tools: a response to Samach.

In a recent paper, we described for the first time the effects of fruit on the expression of putative homologues of genes involved in flowering pathways. It was our aim to provide insight into the molecular mechanisms underlying alternate bearing in citrus. However, a bioinformatics-based critique of our and other related papers has been given by Samach in the preceding Viewpoint article in this issue of Annals of Botany.

Self-pollination and parthenocarpic ability in developing ovaries of self-incompatible Clementine mandarins (Citrus clementina).

This study aimed to determine if self-pollination is needed to trigger facultative parthenocarpy in self-incompatible Clementine mandarins (Citrus clementina Hort. ex Tan.).

Fruit load modulates flowering-related gene expression in buds of alternate-bearing 'Moncada' mandarin.

Background And Aims: Gene determination of flowering is the result of complex interactions involving both promoters and inhibitors. In this study, the expression of flowering-related genes at the meristem level in alternate-bearing citrus trees is analysed, together with the interplay between buds and leaves in the determination of flowering.

Methods: First defruiting experiments were performed to manipulate blossoming intensity in 'Moncada' mandarin, Citrus clementina.

Relationship between soil temperature and fruit colour development of 'Clemenpons' Clementine mandarin (Citrus clementina Hort ex. Tan).

Background: In Citrus, root temperature regulates rind colouration. However, few studies have investigated the range of temperatures and timing which determine rind colour break. The objective of this study was to determine the relationship between range of soil temperature (ST) and rind colour development in the precocious ‘Clemenpons’ Clementine mandarin.

Fruit regulates seasonal expression of flowering genes in alternate-bearing 'Moncada' mandarin.

Background And Aims: The presence of fruit has been widely reported to act as an inhibitor of flowering in fruit trees. This study is an investigation into the effect of fruit load on flowering of 'Moncada' mandarin and on the expression of putative orthologues of genes involved in flowering pathways to provide insight into the molecular mechanisms underlying alternate bearing in citrus.

Methods: The relationship between fruit load and flowering intensity was examined first.

Timing of the inhibitory effect of fruit on return bloom of 'Valencia' sweet orange (Citrus sinensis (L.) Osbeck).

Background: In Citrus the inhibitory effect of fruit on flower formation is the main cause of alternate bearing. Although there are some studies reporting the effect on flowering of the time of fruit removal in a well-defined stage of fruit development, few have investigated the effect throughout the entire fruit growth stage from early fruitlet growth to fruit maturity. The objective of this study was to determine the phenological fruit developmental stage at which the fruit begins its inhibitory effect on flowering in sweet orange by manual removal of fruits, and the role of carbohydrates and nitrogen in the process.