Linkage mapping identifies a non-synonymous mutation in FLOWERING LOCUS T (FT-B1) increasing spikelet number per spike

Abstract

Total spikelet number per spike (TSN) is a major component of spike architecture in wheat (Triticumaestivum L.). A major and consistent quantitative trait locus (QTL) was discovered for TSN in a doubled haploid spring wheat population grown in the field over 4 years. The QTL on chromosome 7B explained up to 20.5% of phenotypic variance. In its physical interval (7B: 6.37–21.67 Mb), the gene FLOWERINGLOCUST (FT-B1) emerged as candidate for the observed effect. In one of the parental lines, FT-B1 carried a non-synonymous substitution on position 19 of the coding sequence. This mutation modifying an aspartic acid (D) into a histidine (H) occurred in a highly conserved position. The mutation was observed with a frequency of ca. 68% in a set of 135 hexaploid wheat varieties and landraces, while it was not found in other plant species. FT-B1 only showed a minor effect on heading and flowering time (FT) which were dominated by a major QTL on chromosome 5A caused by segregation of the vernalization gene VRN-A1. Individuals carrying the FT-B1 allele with amino acid histidine had, on average, a higher number of spikelets (15.1) than individuals with the aspartic acid allele (14.3) independent of their VRN-A1 allele. We show that the effect of TSN is not mainly related to flowering time; however, the duration of pre-anthesis phases may play a major role.

Identification and Validation of a QTL for Spikelet Number on Chromosome Arm 6BL of Common Wheat (Triticum Aestivum L.)

“…In Fort Collins 2020, spikelet number and heading date were positively correlated in the COP-RIL population (r = 0.37, CI95 = 0.25 -0.48, P < 0.0001), consistent with previous observations (Shaw et al 2013;Chen et al 2020;Brassac et al 2021). Among individual loci, variation in PPD-B1 and VRN-D3 were signi cantly associated with heading date (P < 0.0001, Table S7)).…”

“…A single nucleotide insertion in the Vrn-D3b allele creates a frame shift mutation conferring a later heading date compared to plants carrying the Vrn-D3a allele (Bonnin et al 2008;Wang et al 2009;Chen et al 2010). The later heading date conferred by a homoeologous Vrn-B3b allele (referred to as TaFT-B1a) is associated with increased spikelet number and is proposed to be caused by a non-synonymous SNP (Brassac et al 2021). Allelic variation in PPD1 and VRN3 genes have been broadly utilized in wheat breeding programs to optimize heading date for speci c target environments (Nishida et al 2013 (Ikeda et al 2005(Ikeda et al , 2007.…”

Identification and characterization of a natural polymorphism in FT-A2 associated with increased number of grains per spike in wheat

“…Another good example is the main wheat photoperiod gene PHOTOPERIOD1 (PPD1), which shows a strong correlation between heading date and SNS in lines carrying different dosages of PPD1 loss-of-function mutations (R 2 = 0.74) (Shaw et al 2013). A correlation between heading date and SNS has also been observed in genes regulated by PPD1 such as the FLOWERING LOCUS T1 gene (FT1) (Brassac et al 2021;Finnegan et al 2018;Isham et al 2021;Lv et al 2014).…”

Overexpression of the WAPO-A1 gene increases the number of spikelets per spike in bread wheat

“…SPS is affected by genes affecting flowering time through vernalization, photoperiod or earliness per se (eps) pathways: VRN1, FUL2, FUL3, PPD1, VRN3/FT1, FT2, ELF3 [3][4][5][6][7] . Spring or winter growth habit is determined primarily by variation in the VRN genes.…”