# A major FT/TFL1 regulatory locus (Meflwr13) controls flowering time in cassava and provides validated markers for accelerated breeding

## TL;DR

Researchers identified a key genetic region in cassava that controls flowering time and developed markers to speed up breeding.

## Contribution

Discovery of a major regulatory locus (Meflwr13) and validated molecular markers for marker-assisted selection in cassava breeding.

## Key findings

- A QTL on chromosome 13 (Meflwr13) explains 42.63% of phenotypic variation in flowering time.
- Three SNPs (C13_889929, C13_634483, and C13_658450) were validated as predictive markers across diverse cassava backgrounds.
- The locus contains antagonistic floral switch genes FT and TFL1, modulated by WRKY75, AP2/ERF, and TEOSINTE BRANCHED 1.

## Abstract

Flowering in cassava (Manihot esculenta Crantz) is crucial for botanical seed production in breeding programs, but genetic improvement is severely hindered by highly variable, late, or absent flowering in many farmer-preferred genotypes. This challenge prolongs breeding cycles and necessitates costly, labor-intensive flower induction technologies. To overcome these challenges, we aimed to dissect the genetic architecture of this trait and develop molecular markers to facilitate marker-assisted selection (MAS).

Quantitative trait locus (QTL) mapping was conducted in an F₂ population (AM1588) using a categorical 0–2 scoring scale across five time points (4, 6, 7, 8, and 9 months after planting [MAP]).

We identified QTL on chromosomes 1, 7, 13, and 16 with a stable and highly significant QTL on chromosome 13 (Meflwr13), reaching a maximum LOD of 20.82 and explaining up to 42.63% of the phenotypic variation. Fine mapping of Meflwr13 revealed a complex regulatory hub containing the antagonistic master floral switch genes, FLOWERING LOCUS T (FT) and TERMINAL FLOWER 1 (TFL1), along with key transcriptional modulators, including WRKY75, AP2/ERF and TEOSINTE BRANCHED 1 transcription factors.

This molecular architecture strongly suggests that flowering time in this population is controlled by the balance of promoting and repressing factors at this locus. To facilitate direct application, we validated key single nucleotide polymorphisms (SNPs) from Meflwr13 in an independent panel of 304 breeding progenitors. Three SNPs (C13_889929, C13_634483, and C13_658450) exhibited a dominant segregation pattern and showed favorable performance metrics, confirming their predictive power across diverse genetic backgrounds. These validated dominant markers provide breeders with an efficient, cost-effective tool for MAS, enabling rapid screening of seedlings in the nursery. Utilization of these markers will significantly accelerate the production of new, superior cassava varieties.