How beans learned to flower earlier
image: Effect of day length on flowering time and developmental traits in NILs carrying different alleles of PvE1. Plants were grown under long-day (LD2022, 16 h light) and short-day (SD2022, 11 h light) conditions. (A) Close-up images of axillary meristems at ~30 days after emergence (DAE) used as a proxy for the timing of floral induction. NIL026-e1 and PHA0595 exhibit visible flower buds, whereas NIL026-E1 and PHA1037 retain vegetative meristems under LD, indicating delayed floral transition. Days to Flowering (DTF) for each genotype are included in the image. VM, Vegetative Meristem; IM, Inflorescence Meristem; BF, Flower Buds. (B–E) Phenotypic analysis of DTF (B), DTIP (C), NNF (D), and TPH (E). PHA1037, which did not flower, was assigned a DTF value of 200 days. Statistical significance for NIL026-E1 vs. NIL026-e1 was assessed using pairwise Student’s t-test; ***, **, and ns indicate significant differences between NILs at P < 0.001, P < 0.01, and no significant difference, respectively.
Credit: Horticulture Research
Flowering time can determine whether a crop adapts, yields, or fails. In common bean (Phaseolus vulgaris), one of the world’s most important food legumes, sensitivity to day length has shaped where the crop can be grown. A new study identifies PvE1 as a key genetic regulator that delays flowering under long-day (LD) conditions by repressing flowering-promoting PvFT genes. Naturally occurring variants of PvE1, including a 34-base-pair deletion and a frameshift mutation, were associated with earlier flowering and reduced photoperiod sensitivity. The findings provide breeders with new genetic targets for developing early-flowering, day-neutral bean cultivars better suited to temperate and high-latitude regions.
Common bean was domesticated from tropical ancestors that typically flowered under short-day (SD) conditions. As the crop moved into temperate regions, reduced photoperiod sensitivity became essential for stable production under longer summer days. Previous studies had identified PvCOL2 and PvPHYA3 as important regulators of flowering adaptation, but the wider genetic network controlling long-day (LD) flowering remained incomplete. In legumes, flowering pathways often differ from the well-known Arabidopsis model, making crop-specific studies especially important. Due to these challenges, in-depth research is needed to clarify how common bean integrates light, circadian rhythm, and florigen signals to control flowering.
Researchers from Misión Biológica de Galicia-CSIC and the Centro de Investigación en Biotecnología Agroalimentaria (CIAIMBITAL), Universidad de Almería, published (DOI: 10.1093/hr/uhag021) the study on January 22, 2026, in Horticulture Research. The work identifies PvE1 as a conserved legume-specific floral repressor that regulates photoperiod sensitivity and flowering time in common bean, opening a practical route toward breeding climate-adapted cultivars.
The team first fine-mapped two flowering-time quantitative trait loci (QTLs) on chromosome 9 and narrowed the candidate region to a 223-kilobase interval containing 15 annotated genes. Among them, PvE1 stood out because it resembles soybean E1, a known flowering repressor, and because the early-flowering parent carried a 34-base-pair deletion in its 3′ untranslated region (3′ UTR). Using near-isogenic lines (NILs), the researchers showed that plants carrying the e1-del allele flowered much earlier than those with the functional E1 allele under LD conditions. In one genetic background, e1-del plants flowered 29 days earlier and also developed fewer nodes and shorter plants, linking PvE1 to both flowering time and plant architecture. Expression analyses showed that PvE1 follows a circadian rhythm under LD conditions and acts downstream of PvPHYA3. The study further found that PvE1 and PvCOL2 act through partially redundant pathways that converge on the repression of PvFTa3, PvFTb1, and PvFTc.
The authors said the results help explain how common bean adapted from tropical SD environments to regions with longer growing-season daylight. They said PvE1 works like a genetic brake: when functional, it delays flowering under LD conditions by suppressing florigen signals; when weakened by natural mutations, that brake is released, allowing earlier flowering. They also said the discovery connects common bean to a broader legume flowering network while revealing species-specific differences that breeders need to consider.
The application value lies in the rare PvE1 alleles identified in the study. The researchers found two variants, e1-del and e1-fs, both associated with early flowering and reduced photoperiod sensitivity, especially when combined with col2 mutations. These alleles may help breeders develop common bean varieties that flower reliably across broader latitudes, production systems, and changing climate conditions. By offering a new genetic entry point for controlling flowering time, the work could support yield stability, shorten breeding cycles, and expand common bean cultivation beyond traditional growing regions.
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References
DOI
Original Source URL
https://doi.org/10.1093/hr/uhag021
Funding information
This work was supported by the Spanish Ministry of Science, Innovation and Universities (MCIU) through grants CPP2021-008697 (+BEAN), PID2023-147984OB-I00 and PID2023-151867OB-C31, co-funded by AEI/FEDER, EU.
About Horticulture Research
Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2023. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.