Genetic variability of spelt factor gene in Triticum and Aegilops species

Genomic insights into the origin and evolution of spelt (Triticum spelta L.) as a valuable gene pool for modern wheat breeding

Spelt (Triticum aestivum ssp. spelta) is an important wheat subspecies mainly cultivated in Europe before the 20th century that has contributed to modern wheat breeding as a valuable genetic resource. However, relatively little is known about the origins and maintenance of spelt populations. Here, using resequencing data from 416 worldwide wheat accessions, including representative spelt wheat, we demonstrate that European spelt emerged when primitive hexaploid wheat spread to the west and hybridized with pre-settled domesticated emmer, the putative maternal donor. Genomic introgression regions from domesticated emmer confer spelt's primitive morphological characters used for species taxonomy, such as tenacious glumes and later flowering. We propose a haplotype-based "spelt index" to identify spelt-type wheat varieties and to quantify utilization of the spelt gene pool in modern wheat cultivars. This study reveals the genetic basis for the establishment of the spelt wheat subspecies in a specific ecological niche and the vital role of the spelt gene pool as a unique germplasm resource in modern wheat breeding.

Archetypes of inflorescence: genome-wide association networks of panicle morphometric, growth, and disease variables in a multiparent oat population

There is limited information regarding the morphometric relationships of panicle traits in oat (Avena sativa) and their contribution to phenology and growth, physiology, and pathology traits important for yield. To model panicle growth and development and identify genomic regions associated with corresponding traits, 10 diverse spring oat mapping populations (n = 2,993) were evaluated in the field and 9 genotyped via genotyping-by-sequencing. Representative panicles from all progeny individuals, parents, and check lines were scanned, and images were analyzed using manual and automated techniques, resulting in over 60 unique panicle, rachis, and spikelet variables. Spatial modeling and days to heading were used to account for environmental and phenological variances, respectively. Panicle variables were intercorrelated, providing reproducible archetypal and growth models. Notably, adult plant resistance for oat crown rust was most prominent for taller, stiff stalked plants having a more open panicle structure. Within and among family variance for panicle traits reflected the moderate-to-high heritability and mutual genome-wide associations (hotspots) with numerous high-effect loci. Candidate genes and potential breeding applications are discussed. This work adds to the growing genetic resources for oat and provides a unique perspective on the genetic basis of panicle architecture in cereal crops.

A Multi-Omics Approach for Rapid Identification of Large Genomic Lesions at the Wheat Dense Spike (wds) Locus

Optimal spike architecture provides a favorable structure for grain development and yield improvement. However, the number of genes cloned to underlie wheat spike architecture is extremely limited. Here, we obtained a wheat dense spike mutant (wds) induced by 60Co treatment of a common wheat landrace Huangfangzhu that exhibited significantly reduced spike and grain lengths. The shortened spike length was caused by longitudinal reduction in number and length of rachis cells. We adopted a multi-omics approach to identify the genomic locus underlying the wds mutant. We performed Exome Capture Sequencing (ECS) and identified two large deletion segments, named 6BL.1 at 334.8∼424.3 Mb and 6BL.2, 579.4∼717.8 Mb in the wds mutant. RNA-seq analysis confirmed that genes located in these regions lost their RNA expression. We then found that the 6BL.2 locus was overlapping with a known spike length QTL, qSL6B.2. Totally, 499 genes were located within the deleted region and two of them were found to be positively correlated with long spike accessions but not the ones with short spike. One of them, TraesCS6B01G334600, a well-matched homolog of the rice OsBUL1 gene that works in the Brassinosteroids (BR) pathway, was identified to be involved in cell size and number regulation. Further transcriptome analysis of young spikes showed that hormone-related genes were enriched among differentially expressed genes, supporting TraesCS6B01G334600 as a candidate gene. Our work provides a strategy to rapid locate genetic loci with large genomic lesions in wheat and useful resources for future wheat study.

A Combinatorial Q-locus and Tubulin-Based Polymorphism (TBP) Approach Helps in Discriminating Triticum Species

The simple and straightforward recognition of Triticum species is not an easy task due to their complex genetic origins. To provide a recommendation, we have compared the performance of different PCR-based methods relying on the discrimination ability of the Q- and γ-gliadin (GAG56D) genes, as well as TBP (Tubulin-Based Polymorphism), a method based on the multiple amplification of genes of the β-tubulin family. Among these approaches, the PCR-RFLP (Restriction Fragment Length Polymorphism) assay based on a single-nucleotide polymorphism (SNP) present in the Q gene is the only one capable of fully discerning hexaploid spelt and common wheat species, while both γ-gliadin and TBP fail with similar error frequencies. The Q-locus assay results in the attainment of either a single fragment or a doublet, depending on the presence of a suitable restriction site, which is affected by the mutation. This dual pattern of resolution limits both the diagnostic effectiveness, when additional Triticum species are assayed and compared to each other, and its usefulness, when commercially available flours are analyzed. These limitations are overtaken by flanking the Q-locus assay with the TBP analysis. In this way, almost all of the Triticum species can be accurately identified.

Genetic Features of Triticale–Wheat Hybrids with Vaviloid-Type Spike Branching

Vaviloid spike branching, also called sham ramification, is a typical trait of Triticum vavilovii Jakubz. and is characterized by a lengthening of the spikelet axis. In this article, we present the results of a study of three triticale–wheat hybrid lines with differences in terms of the manifestation of the vaviloid spike branching. Lines were obtained by crossing triticale with hexaploid wheat, T. aestivum var. velutinum. The parental triticale is a hybrid of synthetic wheat (T. durum × Ae. tauschii var. meyrei) with rye, S. cereale ssp. segetale. Line 857 has a karyotype corresponding to hexaploid wheat and has a spike morphology closest to normal, whereas Lines 808/1 and 844/4 are characterized by the greatest manifestation of vaviloid spike branching. In Lines 808/1 and 844/4, we found the substitution 2RL(2DL). The karyotypes of the latter lines differ in that a pair of telocentric chromosomes 2DS is detected in Line 808/1, and these telocentrics are fused into one unpaired chromosome in Line 844/4. Using molecular genetic analysis, we found a deletion of the wheat domestication gene Q located on 5AL in the three studied hybrid lines. The deletion is local since an analysis of the adjacent gene B1 showed the presence of this gene. We assume that the manifestation of vaviloid spike branching in two lines (808/1 and 844/4) is associated with a disturbance in the joint action of genes Q and AP2L2-2D, which is another important gene that determines spike morphology and is located on 2DL.

Publisher Correction to: BMC Plant Biology, Volume 20, supplement 1

An amendment to this paper has been published and can be accessed via the original article.