Cowpea is an annual legume crop; although it is an essential food in developing countries, cowpea is now grown worldwide. For the genetic improvement of plants, flowering time is one of the major selection criteria. In general, flowering is regulated by photoperiod and temperature, along with the interaction between environmental factors. In this study, we aimed to investigate the candidate genes associated with flowering time using genome-wide association study (GWAS). To investigate the flowering time-related genes, 384 cowpea germplasms were genotyped with 51,128 single nucleotide polymorphisms (SNPs). The main genetic component of days to flowering (DTF) was analyzed using genome association and prediction integrated tool (GAPIT) and elastic-net analyses. From the GAPIT and elastic-net analyses, a total of 23 SNPs were significantly associated with DTF among five (chr. 2, 3, 7, 9, and 11) and seven (chr. 1, 2, 3, 4, 5, 8, and 9) different chromosomes, respectively. Based on our analysis, Vigun01g084000, Vigun01g227200, Vigun02g062600, and Vigun03g296800 were considered the major candidate genes that were significantly associated with DTF in cowpea. These results confirmed that DTF might be controlled by multiple genes affecting early flowering, delaying flowering time, repressing the transition to flowering, etc. This study will potentially contribute to effective DTF genomic selection in plant breeding to better understand the genetic basis and explore the mechanism of flowering time.

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• Genome-wide association studies dissect the genetic architecture of seed and yield component traits in cowpea (Vigna unguiculata L. Walp)
  Habib Akinmade, Rebecca Caroline Ulbricht Ferreira, Mario Henrique Murad Leite Andrade, Claudio Fernandes, Pablo Sipowicz, María Muñoz-Amatriaín, Esteban Rios, T Jamann
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Flowering time (heading date) of the rice plant is considered an important agronomic trait for environmental adaptation and grain yield. It is controlled by multiple genes and is regulated by different environmental factors, such as day length, temperature, soil moisture, etc. So far, approximately 125 genes regulating flowering process and floral organ identity or development directly or indirectly have been reported in rice. Among these genes, Heading date 3a (Hd3a), RICE FLOWERING LOCUS T1 (RFT1), Heading date 5 (Hd5), MORF-RELATED GENE702 (MRG702), Casein kinases, CKI and CK2α, Pseudo-Response Regulator 37 (PRR37), Hd gene family have been reported as the key genes regulating flowering time in rice; however, their functions are mostly inter-related. Hd3a and RFT1 that encode florigens, are known as the floral transition genes in rice. In rice, florigen immediately induces downstream genes in the shoot apical meristem (SAM) to start the transition from vegetative to reproductive phase. RFT1 gene regulates flowering time with pivotal action while Hd3a, regulates under long day conditions. The Hd5 gene regulates flowering time in variation of early heading for adaptation depending on environmental signals. MRG702, a reader protein, promotes flowering. Casein kinases, CKI and CK2α directly influence the function of the early heading regulator PRR37. Hd16/CKI hinders flowering time in the Ehd1-concerned pathway through phosphorylation of Ghd7 and PRR37. Natural variants of Hd1, PRR37, Ghd7, DTH8, Hd6, and Hd16 were found in the rice varieties that are cultivated presently in Asia and Europe, and their variants play significant roles in the down streaming of Ehd1 expression to delay flowering time in natural long day (LD) conditions.

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• Exogenous and Endogenous Signals: Critical Factors for Regulation of Flowering Time and Grain Yield in Rice
  E. Kariali, S. Panigrahi, P. K. Suna, P. K. Senapati, R. Das, P. Dwivedi
  Russian Journal of Plant Physiology.2025;[Epub]     CrossRef
• CRISPR-Cas technology based genome editing for modification of salinity stress tolerance responses in rice (Oryza sativa L.)
  Ibrahim Khan, Sikandar Khan, Yong Zhang, Jianping Zhou, Maryam Akhoundian, Sohail Ahmad Jan
  Molecular Biology Reports.2021; 48(4): 3605.     CrossRef

Flowering time is a very important agronomic trait in Brassica crops and regulation of the time is one of major factor in the breeding program. To understand the control of flowering time in Brassica rapa, we have carried out Br300K microarray with two contrasting Brassica inbred lines, Rapid Cycling B. rapa (RCBr) as rapid cycling type and B. rapa ssp. pekinensis inbred line Chiifu as slow flowering phenotype. Reproductive process-related genes were specifically expressed in RCBr, whereas environmental stimuli-responsive genes in Chiifu. Flowering stimulating genes, such as BrFT and BrSOC1, were preferentially expressed in RCBr, while flowering repressing genes, such as BrFLC and BrMAF4, expressed in Chiifu. Several paralogues present in B. rapa, BrFLCs and BrCOLs, were expressed with paralog-specific pattern depending on flowering phenotypes: i.e., BrFLC1 and BrFLC2, major floral repressors, were expressed in Chiifu, BrFLCL/BrFLC5 in RCBr and BrFLC3 in both plants. The expression of several flowering repressing genes was gradually decreased in RCBr growth, but increased in Chiifu growth. However, the expression of genes involved in photoperiodic flowering was no difference between these two plants under LD and SD conditions, indicating photoperiodic pathway is not major factor to distinguish fast vs. slow flowering in B. rapa. The mechanism underlined in the rapid or fast flowering of RCBr would be further elucidated in association with the controlling mechanism of its short life span.

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• Homeologs of Brassica SOC1, a central regulator of flowering time, are differentially regulated due to partitioning of evolutionarily conserved transcription factor binding sites in promoters
  Tanu Sri, Bharat Gupta, Shikha Tyagi, Anandita Singh
  Molecular Phylogenetics and Evolution.2020; 147: 106777.     CrossRef
• Genome-wide analysis of spatiotemporal gene expression patterns during floral organ development in Brassica rapa
  Soo In Lee, Muthusamy Muthusamy, Muhammad Amjad Nawaz, Joon Ki Hong, Myung-Ho Lim, Jin A. Kim, Mi-Jeong Jeong
  Molecular Genetics and Genomics.2019; 294(6): 1403.     CrossRef
• Genome-wide identification of flowering time genes associated with vernalization and the regulatory flowering networks in Chinese cabbage
  Won Yong Jung, Areum Lee, Jae Sun Moon, Youn-Sung Kim, Hye Sun Cho
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• Genome-wide analysis of gene expression to distinguish photoperiod-dependent and -independent flowering in Brassicaceae
  Hayoung Song, Hankuil Yi, Changhee Do, Ching-Tack Han, Ill-Sup Nou, Yoonkang Hur
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