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.
Highlights
In light of a growing world population, the increase of wheat yield and the genetic mechanisms behind are of immediate interest
The doubled haploid (DH) population-2 described in Muqaddasi et al.[35] was grown on the field and characterized for 4 years (2016–2019) for total spikelet number (TSN) per spike, spike length (SL), heading date (HD), and flowering time (FT)
The FLOWERING LOCUS T (FT-B1) gene located in the most significant quantitative trait loci (QTL) interval (7B: 6.3–21.7 Mb) was considered as most likely candidate for the observed effect on total spikelet number per spike (TSN), because (1) FT-B1 carried a non-synonymous mutation causing an amino acid exchange in the parental lines, (2) a QTL analysis including the Kompetitive Allele Specific PCR (KASP) marker based on the mutation confirmed its significant association with TSN, and (3) FT-B1 was previously associated with effects on spikelet number in the literature
Summary
In light of a growing world population, the increase of wheat yield and the genetic mechanisms behind are of immediate interest. Compared to the two other gene families, FT-like genes, evolving via small- and large-scale duplications, are the most numerous among monocots with 13 paralogs identified in rice, five in barley, and nine in wheat based on expressed sequences tags (ESTs) data[31,32] Due to their impact on the phenology and flowering architecture of crops, FT-like genes have been a target of selection during domestication and subsequent range expansion to adapt to new e nvironments[33,34]. We performed linkage mapping to investigate the genetic basis of total spikelet number per spike and its associated traits viz., spike length, heading date, and flowering time in a doubled haploid spring wheat population. We investigated the interaction of FT-B1 with the vernalization gene VRN-A1 that segregated in the studied population
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