Mass Spectrometry Imaging Disclosed Spatial Distribution of Defense-Related Metabolites in Triticum spp.

Fusarium Head Blight is the most common fungal disease that strongly affects Triticum spp., reducing crop yield and leading to the accumulation of toxic metabolites. Several studies have investigated the plant metabolic response to counteract mycotoxins accumulation. However, information on the precise location where the defense mechanism is taking place is scarce. Therefore, this study aimed to investigate the specific tissue distribution of defense metabolites in two Triticum species and use this information to postulate on the metabolites’ functional role, unlocking the “location-to-function” paradigm. To address this challenge, transversal cross-sections were obtained from the middle of the grains. They were analyzed using an atmospheric-pressure (AP) SMALDI MSI source (AP-SMALDI5 AF, TransMIT GmbH, Giessen, Germany) coupled to a Q Exactive HF (Thermo Fisher Scientific GmbH, Bremen, Germany) orbital trapping mass spectrometer. Our result revealed the capability of (AP)-SMALDI MSI instrumentation to finely investigate the spatial distribution of wheat defense metabolites, such as hydroxycinnamic acid amides, oxylipins, linoleic and α-linoleic acids, galactolipids, and glycerolipids.

Virulence of Pyrenophora tritici-repentis: a minireview

Pyrenophora tritici-repentis is a major wheat pathogen in all wheat (Triticum spp.) growing areas worldwide. Up to date, eight P. tritici-repentis races have been described based on chlorosis, necrosis, or both symptoms caused on race differential wheat genotypes: ‘Glenlea’, 6B662, 6B365, and ‘Salamouni’. Symptom development on differential genotypes depends on the interaction of the pathogen’s necrotrophic effectors named Ptr ToxA, Ptr ToxB, and Ptr ToxC with host susceptibility genes. Ptr ToxA is encoded by the single copy gene ToxA and induces necrosis on sensitive wheat cultivars. Ptr ToxB causes chlorosis and is encoded by the multicopy gene ToxB. The Ptr ToxC is the non-proteinaceous, polar, low molecular mass molecule that also induces chlorosis, but up to date, the gene encoding this toxin is unknown. Races producing Ptr ToxA are predominant in the global Ptr population. There are several reports about new putative races of P. tritici-repentis that do not conform with the current race system, so further research is required. This study aims to collect and systematise available information about the virulence and races of P. tritici-repentis.

Distribution of Puccinia striiformis f. sp. tritici races and virulence in wheat growing regions of Kenya from 1970 TO 2014

Stripe rust, caused by the fungal pathogen Puccinia striiformis f. sp. tritici (Pst), is a major threat to wheat (Triticum spp.) production worldwide. The objective of this study was to determine the virulence of Pst races prevalent in the main wheat growing regions of Kenya, which includes Mt. Kenya, Eastern Kenya, and the Rift Valley (Central, Southern, and Northern Rift). Fifty Pst isolates collected from 1970 to 1992 and from 2009 to 2014 were virulence phenotyped using stripe rust differential sets, and 45 isolates were genotyped with sequence characterized amplified region (SCAR) markers to differentiate among the isolates and identify aggressive strains PstS1 and PstS2. Virulence corresponding to stripe rust resistance genes Yr1, Yr2, Yr3, Yr6, Yr7, Yr8, Yr9, Yr17, Yr25, Yr27 and the seedling resistance in genotype Avocet S were detected. Ten races were detected in the Pst samples obtained from 1970 to 1992, and three additional races were detected from 2009 to 2014, with a single race being detected in both periods. The SCAR markers detected both Pst1 and Pst2 strains in the collection. Increasing Pst virulence was found in the Kenyan Pst population, and that diverse Pst race groups dominated different wheat growing regions. Moreover, recent Pst races in east Africa indicated possible migration of some race groups into Kenya from other regions. This study is important in understanding Pst evolution and virulence diversity and useful in breeding wheat cultivars with effective resistance to stripe rust. Keywords: pathogenicity, Puccinia f. sp. tritici stripe (yellow) rust, Triticum aestivum

Genome sequences of Aegilops species of section Sitopsis reveal phylogenetic relationships and provide resources for wheat improvement

Aegilops is a close relative of wheat (Triticum spp.), and Aegilops species in the section Sitopsis represent a rich reservoir of genetic diversity for improvement of wheat. To understand their diversity and advance their utilization, we produced whole-genome assemblies of Ae. longissima and Ae. speltoides. Whole-genome comparative analysis, along with the recently sequenced Ae. sharonensis genome, showed that the Ae. longissima and Ae. sharonensis genomes are highly simiar and most closely related to the wheat D subgenome. By contrast, the Ae. speltoides genome is more closely related to the B subgenome. Haplotype block analysis supported the idea that Ae. speltoides is the closest ancestor of the wheat B subgenome and highlighted variable and similar genomic regions between the three Aegilops species and wheat. Genome-wide analysis of nucleotide-binding site leucine rich repeat (NLR) genes revealed species-specific and lineage-specific NLR genes and variants, demonstrating the potential of Aegilops genomes for wheat improvement.

Viscoelastic properties of wheat gluten in a molecular dynamics study

Wheat (Triticum spp.) gluten consists mainly of intrinsincally disordered storage proteins (glutenins and gliadins) that can form megadalton-sized networks. These networks are responsible for the unique viscoelastic properties of wheat dough and affect the quality of bread. These properties have not yet been studied by molecular level simulations. Here, we use a newly developed α-C-based coarse-grained model to study ∼ 4000-residue systems. The corresponding time-dependent properties are studied through shear and axial deformations. We measure the response force to the deformation, the number of entanglements and cavities, the mobility of residues, the number of the inter-chain bonds, etc. Glutenins are shown to influence the mechanics of gluten much more than gliadins. Our simulations are consistent with the existing ideas about gluten elasticity and emphasize the role of entanglements and hydrogen bonding. We also demonstrate that the storage proteins in maize and rice lead to weaker elasticity which points to the unique properties of wheat gluten.

Morphological, Physiological, and Biochemical Characterization of Drought-Tolerant Wheat (Triticum spp.) Varieties

Wheat is one of the most important cereal crops and extensively cultivated in wide ranges of altitudes in Ethiopia. With an alarming population growth in the era of climatic change, there is a need for further crop improvement for sustainable production. In this regard, the study was carried out at the Kulumsa Agricultural Research Center (KARC) in a rainout shelter to investigate the responses of durum and bread wheat varieties to soil water stress in terms of selected morphological, physiological, and biochemical parameters. The 2 factors were combined factorially and arranged in a randomized complete block design with 3 replications. The 12 wheat varieties, 6 bread wheat and other 6 durum wheat, were sown in pots under well-watered (100% field capacity) and water-stressed (30% field capacity) conditions. Results revealed that water stress resulted in 26%, 9%, 23%, 16%, and 11% reductions in plant height, spike length, number of spikelets spike−1, relative water, and chlorophyll contents, respectively. The tested wheat varieties under water stress produced 28% and 6% more proline content and total soluble sugar, respectively, as mitigation strategies against drought. Results further exhibited that wheat varieties significantly differed in all of the measured traits except for the plant height and relative water content. The present study verified that the biochemical parameters needs to be considered as better traits to select wheat (Triticum spp.) varieties for drought tolerance under water stress conditions.

EVALUATION OF LODGING RESISTANCE AMONG THE DIFFERENT WHEAT SPECIES (TRITICUM SPP.) IN THE CONDITIONS OF ABSHERON

The article presents the results of field research on the comparative study of lodging resistance among the different wheat species (Triticum spp.) in relation with the associated morphological traits in 2018-2021.