Additive QTLs on three chromosomes control flowering time in woodland strawberry (Fragaria vesca L.)

Samia Samad,Daniel James Sargent,Elli Koskela,Vipul Patel,Katriina Mouhu,Takeshi Kurokura,Tuomas Toivainen,Timo Hytönen

doi:10.1038/hortres.2017.20

Abstract

Flowering time is an important trait that affects survival, reproduction and yield in both wild and cultivated plants. Therefore, many studies have focused on the identification of flowering time quantitative trait locus (QTLs) in different crops, and molecular control of this trait has been extensively investigated in model species. Here we report the mapping of QTLs for flowering time and vegetative traits in a large woodland strawberry mapping population that was phenotyped both under field conditions and in a greenhouse after flower induction in the field. The greenhouse experiment revealed additive QTLs in three linkage groups (LG), two on both LG4 and LG7, and one on LG6 that explain about half of the flowering time variance in the population. Three of the QTLs were newly identified in this study, and one co-localized with the previously characterized FvTFL1 gene. An additional strong QTL corresponding to previously mapped PFRU was detected in both field and greenhouse experiments indicating that gene(s) in this locus can control the timing of flowering in different environments in addition to the duration of flowering and axillary bud differentiation to runners and branch crowns. Several putative flowering time genes were identified in these QTL regions that await functional validation. Our results indicate that a few major QTLs may control flowering time and axillary bud differentiation in strawberries. We suggest that the identification of causal genes in the diploid strawberry may enable fine tuning of flowering time and vegetative growth in the closely related octoploid cultivated strawberry.

Highlights

Synchronizing floral development with local climatic conditions is important for crop and wild plants because of its significant impact on reproduction, yield and survival
Previous quantitative trait locus (QTLs) mapping studies in strawberry have focused on the perpetual flowering habit,[5,6,8,42] and no QTLs have been reported for earliness
We report the identification of additive QTLs on three linkage groups (LG) that explain over 50% of the observed 18-day variance in flowering time in woodland strawberry mapping population previously reported by Koskela et al.[32]

Summary

Introduction

Synchronizing floral development with local climatic conditions is important for crop and wild plants because of its significant impact on reproduction, yield and survival. Flower induction occurs independently of day-length at temperatures below ~ 13 °C, whereas SDs are required at intermediate temperatures, and at temperatures above 20–24 °C floral induction is inhibited.[10,11,12,13] There is significant variation in critical temperature limits between cultivars,[10,14] and some cultivars possess an obligatory SD requirement for flower induction even under cool temperatures.[15] In contrast to seasonal flowering strawberries, EB cultivars flower earlier under long days (LD) than SDs.[16,17] Both seasonal flowering and EB habits are found in the woodland strawberry.[18]

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Conclusion