TbMYC4A Is a Candidate Gene Controlling the Blue Aleurone Trait in a Wheat-Triticum boeoticum Substitution Line

Triticum boeoticum Boiss (AbAb, 2n = 2x = 14) is one of the sources of the blue grain trait controlled by blue aleurone layer 2 (Ba2). However, the underlying genes have not been cloned. In this study, a transcriptomic comparison between a blue-grained wheat-T. boeoticum substitution line and its wheat parent identified 41 unigenes related to anthocyanin biosynthesis and 29 unigenes related to transport. The bHLH transcription factor gene TbMYC4A showed a higher expression level in the blue-grained substitution line. TbMYC4A contained the three characteristic bHLH transcription factor domains (bHLH-MYC_N, HLH and ACT-like) and clustered with genes identified from other wheat lines with the blue grain trait derived from other Triticeae species. TbMYC4A overexpression confirmed that it was a functional bHLH transcription factor. The analysis of a TbMYC4A-specific marker showed that the gene was also present in T. boeoticum and T. monococcum with blue aleurone but absent in other Triticeae materials with white aleurone. These results indicate that TbMYC4A is a candidate gene of Ba2 controlling the blue aleurone trait. The isolation of TbMYC4A is helpful for further clarifying the genetic mechanism of the blue aleurone trait and is of great significance for breeding blue-grained wheat varieties.

Differentiation of eiincorns by water retention capacity

Aim. On the basis of multivariate analysis, to differentiate einkorn wheat accessions by the water-holding capacity of leaves and ears and the parameters of these organs at the level of species and genotypes. Methods. The water-holding capacity was assessed by the moisture-yielding coefficient which was determined by the method of N.N. Kozhushko (Kozhushko, 1988). Differentiation of einkorn samples was carried out by the method of principal components in the interpretation of A.V. Korosov (Korosov, 1996). Results. Triticum monococcum UA0300113, Syria, and UA0300282, Hungary were characterized by the lowest specific moisture-yielding coefficients: for the second and flag leaves, respectively, (mg / cm2) 10.9, 7.0 and 11.4, 10.7; ears – the same samples as well as Triticum boeoticum UA0300401, Ukraine-Crimea: (mg / cm) 29.6, 28.2, 25.4. With an increase in the size of the lamina, there is a tendency to a decrease in its specific moisture yield. The samples of eincorn are differentiated into 4 clusters corresponding to the species. Conclusions. T. monococcum UA0300113, Syria, and UA0300282, Hungary are relatively drought tolerant. The complex of features characterizing leaf and spike size in combination with the moisture-yielding coefficients processed by the method of principal components makes it possible to differentiate einkorn oaccessions by species and genotype. Keywords: einkorns, moisture yield, drought resistance, leaf, ear.

Identification of a recessive gene YrZ15-1370 conferring adult plant resistance to stripe rust in wheat-Triticum boeoticum introgression line

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most damaging diseases of wheat globally and resistance is the effectively control strategy. Triticum boeoticum Boiss (T. monococcum L. ssp. aegilopoides, 2n = 2x = 14, AbAb) accession G52 confers a high level of adult-plant resistance against a mixture of the Chinese prevalent Pst races. To transfer the resistance to common wheat, a cross was made between G52 and susceptible common wheat genotype Crocus. A highly resistant wheat-T. boeoticum introgression line Z15-1370 (F5 generation) with 42 chromosomes was selected cytologically and by testing with Pst races. In order to map the resistance gene(s), F1, F2, and F2:3 generations of the cross between Z15-1370 and stripe rust susceptible common wheat Mingxian169 were developed. Genetic analysis revealed that the resistance in Z15-1370 was controlled by a single recessive gene, temporarily designated YrZ15-1370. Using the bulked segregant RNA-Seq (BSR-Seq) analysis, YrZ15-1370 was mapped to chromosome 6AL and flanked by markers KASP1370-3 and KASP-1370-5 within a 4.3 cM genetic interval corresponding to 1.8 Mb physical region in the Chinese Spring genome, in which a number of disease resistance-related genes were annotated. YrZ15-1370 differed from previously Yr genes identified on chromosome 6A based on its position and/or origin. The YrZ15-1370 would be a valuable resource for wheat resistance improvement and the flanking markers developed here should be useful tools for marker-assisted selection (MAS) in breeding and further cloning the gene.

Extensive Genetic Variation at the Sr22 Wheat Stem Rust Resistance Gene Locus in the Grasses Revealed Through Evolutionary Genomics and Functional Analyses

In the last 20 years, severe wheat stem rust outbreaks have been recorded in Africa, Europe, and Central Asia. This previously well controlled disease, caused by the fungus Puccinia graminis f. sp. tritici, has reemerged as a major threat to wheat cultivation. The stem rust (Sr) resistance gene Sr22 encodes a nucleotide-binding and leucine-rich repeat receptor which confers resistance to the highly virulent African stem rust isolate Ug99. Here, we show that the Sr22 gene is conserved among grasses in the Triticeae and Poeae lineages. Triticeae species contain syntenic loci with single-copy orthologs of Sr22 on chromosome 7, except Hordeum vulgare, which has experienced major expansions and rearrangements at the locus. We also describe 14 Sr22 sequence variants obtained from both Triticum boeoticum and the domesticated form of this species, T. monococcum, which have been postulated to encode both functional and nonfunctional Sr22 alleles. The nucleotide sequence analysis of these alleles identified historical sequence exchange resulting from recombination or gene conversion, including breakpoints within codons, which expanded the coding potential at these positions by introduction of nonsynonymous substitutions. Three Sr22 alleles were transformed into wheat cultivar Fielder and two postulated resistant alleles from Schomburgk (hexaploid wheat introgressed with T. boeoticum segment carrying Sr22) and T. monococcum accession PI190945, respectively, conferred resistance to P. graminis f. sp. tritici race TTKSK, thereby unequivocally confirming Sr22 effectiveness against Ug99. The third allele from accession PI573523, previously believed to confer susceptibility, was confirmed as nonfunctional against Australian P. graminis f. sp. tritici race 98-1,2,3,5,6. [Formula: see text] Copyright © 2020 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Ecological assembly processes of the bacterial and fungal microbiota of wild and domesticated wheat species

Plant domestication has led to substantial changes in the host physiology. How this anthropogenic intervention has contributed in altering the wheat microbiota is not well understood. Here, we investigated the role of ecological selection, drift and dispersal in shaping the bacterial and fungal communities associated with domesticated wheat Triticum aestivum and two wild relatives, Triticum boeoticum and Triticum urartu. Our study shows that the bacterial and fungal microbiota of wild and domesticated wheat species follow distinct community assembly patterns. Further, we revealed a more prominent role of neutral processes in the assembly of the microbiota of domesticated wheat and propose that domestication has relaxed selective processes in the assembly of the wheat microbiota.

Expression changes in the TaNAC2 and TaNAC69-1 transcription factors in drought stress tolerant and susceptible accessions of Triticum boeoticum

Triticum boeoticum is a valuable gene source for tolerance to drought stress. In order to study the effect of drought stress on this plant, and to understand its adaptive mechanisms at the molecular level, 10 accessions of T. boeoticum were evaluated under non- and drought stress conditions. Evaluation of 31 different phenological, morpho-physiological and root-related traits showed that there were significant differences between accessions. Using the bi-plot resulting from the PCA, the studied traits and accessions were separated in different groups. The most tolerant (B5) and susceptible (B6) accessions to drought stress were identified, so these accessions were used for assessment of changes in the TaNAC2 and TaNAC69-1 transcription factors (TFs) expression. The results showed that in the most tolerant and susceptible accessions, TaNAC2 and TaNAC69-1 expression levels increased between non-stress and stress conditions significantly, but the increased level of these two genes expression in the most tolerant accession was much higher than the most susceptible accession. According to the obtained results, T. boeoticum can be a suitable and promising gene source for improving modern wheat. In addition, the results of TFs expression could improve our understanding about the complex mechanisms associated with drought tolerance in wheat, especially wild wheat.