Identification of successive flowering phases highlights a new genetic control of the flowering pattern in strawberry.

Justine Perrotte,Yann Guédon,Amèlia Gaston,Béatrice Denoyes

doi:10.1093/jxb/erw326

Abstract

The genetic control of the switch between seasonal and perpetual flowering has been deciphered in various perennial species. However, little is known about the genetic control of the dynamics of perpetual flowering, which changes abruptly at well-defined time instants during the growing season. Here, we characterize the perpetual flowering pattern and identify new genetic controls of this pattern in the cultivated strawberry. Twenty-one perpetual flowering strawberry genotypes were phenotyped at the macroscopic scale for their course of emergence of inflorescences and stolons during the growing season. A longitudinal analysis based on the segmentation of flowering rate profiles using multiple change-point models was conducted. The flowering pattern of perpetual flowering genotypes takes the form of three or four successive phases: an autumn-initiated flowering phase, a flowering pause, and a single stationary perpetual flowering phase or two perpetual flowering phases, the second one being more intense. The genetic control of flowering was analysed by quantitative trait locus mapping of flowering traits based on these flowering phases. We showed that the occurrence of a fourth phase of intense flowering is controlled by a newly identified locus, different from the locus FaPFRU, controlling the switch between seasonal and perpetual flowering behaviour. The role of this locus was validated by the analysis of data obtained previously during six consecutive years.

Highlights

Flowering is a key step in the plant life cycle, directly linked to the production potential of crop species
We designed our study to address the following questions. (i) Can we properly characterize the perpetual flowering pattern by a longitudinal analysis of flowering rate profiles relying on minimum a priori assumptions? (ii) Can we identify genetic controls of the dynamics of perpetual flowering using a quantitative trait locus (QTL) approach? (iii) Are these genetic controls related to the previously identified FaPFRU locus and stable in other environments?
The first phase of emergence of inflorescences, between weeks 16 and 19, was synchronized whatever the flowering habit, perpetual flowering’ (PF) or seasonal flowering’ (SF) (Fig. 1). It corresponded to the period of emergence of inflorescences initiated in autumn the previous year and will be referred to as the autumn-initiated flowering (AIF) phase

Summary

Introduction

Flowering is a key step in the plant life cycle, directly linked to the production potential of crop species. The timing and duration of this process are of particular importance for fruit production. In polycarpic perennial plants, flowering usually occurs in a specific seasonal period, the ‘seasonal flowering’ (SF) habit, but some species present genotypes with the ability to initiate flowering during an extended period, offering a lengthened period for flower and fruit production, the ‘perpetual flowering’ (PF) habit, called continuous flowering (de Camacaro et al, 2002; Albani and Coupland, 2010). PF is an attractive agronomical trait, and a better knowledge of its genetic control is a major issue for strawberry breeding. The genetic control of PF has recently been deciphered and this has highlighted the role of floral repressors in the switch between SF and PF in several species.

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Discussion

Conclusion