AAC Whitehead hard white spring wheat

AAC Whitehead, an awned hard white spring wheat (Triticum aestivum L.) cultivar, combines high grain yield and good agronomic characteristics with excellent disease resistance. Based on 34 station-years of registration trial data from 2017 to 2019, AAC Whitehead had grain yield significantly higher than all of the check cultivars. AAC Whitehead had maturity similar to the checks, low lodging scores, and significantly shorter plant height than Snowstar and Whitehawk. AAC Whitehead had significantly lower test weight and higher kernel mass than than all the check cultivars. AAC Whitehead expressed resistance to the prevalent races of leaf, stripe and stem rust, and common bunt; and moderate resistance to Fusarium head blight (FHB). It also expressed tolerance to the orange wheat blossom midge. AAC Whitehead expresses quality attributes within the range of the check cultivars and is eligible for grades of Canada Western Hard White Spring wheat.

Trunk Surgery as a Tool to Reduce Foliar Symptoms in Diseases of the Esca Complex and Its Influence on Vine Wood Microbiota

In the last few years, trunk surgery has gained increasing attention as a method to reduce foliar symptoms typical of some of the Esca complex diseases. The technique relies on the mechanical removal of decayed wood by a chainsaw. A study on a 14-year-old Cabernet Sauvignon vineyard was carried out to validate the efficacy of trunk surgery and explore possible explanations behind it. Three levels of treatment were applied to three of the most characteristic symptoms associated with some diseases of the Esca complex, such as leaf stripe symptoms (LS), wilted shoots (WS) and apoplexy (APP). The most promising results were obtained by complete trunk surgery, where the larger decay removal allowed lower symptom re-expression. According to the wood types analyzed (decay, medium and sound wood), different changes in microbiota were observed. Alpha-diversity generally decreased for bacteria and increased for fungi. More specifically, main changes were observed for Fomitiporia mediterranea abundance that decreased considerably after trunk surgery. A possible explanation for LS symptom reduction after trunk surgery could be the microbiota shifting caused by the technique itself affecting a microbic-shared biochemical pathway involved in symptom expression.

Use of gene family analysis to discover argonaut (AGO) genes for increasing the resistance of Tibetan hull-less barley to leaf stripe disease

Leaf stripe is a common, but major infectious disease of barley, severely affecting the yield and quality. However, only a few genes have been identified by conventional gene mapping. Gene family analysis has become a fast and efficient strategy for gene discovery. Studies demonstrated that Argonaute (AGO) proteins play an important role in plant disease resistance. Thus, we obtained nine HvAGO genes via mRNA sequencing before and after a Pyrenophora graminea infection of a disease-resistant variety "Kunlun 14" and a susceptible variety "Z1141". We analysed the physicochemical characteristics, gene structures, and motifs of the HvAGO gene sequences and found that these proteins were divided into four clusters by evolutionary distance. There was high consistency in the number of exons, size, and the number and type of motifs in the different clusters. Based on protein phylogenetics, they could be divided into three branches. A collinearity analysis of Tibetan hull-less barley and Arabidopsis thaliana, rice, and maize showed that four genes were collinear with respect to the other three species. The qRT-PCR showed the expression levels of HvAGO1, HvAGO2 and HvAGO4 were significantly increased after infection with Pyrenophora graminea. These three members of the AGO gene family are, thus, speculated to play an important role in barley leaf stripe resistance. The results provide reference for the application of HvAGO genes in the leaf stripe control and the exploration of disease resistance genes in other crops.

Identification and Profiling of microRNAs and Their Target Genes in Tibetan Hulless Barley in Response to Barley Leaf Stripe (BLS) Infection

Background Tibetan hulless barley is widely grown on the Qinghai-Tibet Plateau, where it has served as a staple food for Tibetan people since the 5th century CE. Barley leaf stripe (BLS) is one of the most severe fungal diseases affecting the yield and quality of Tibetan hulless barley. Results Here, we compared the miRNA profiles before and after BLS in two Tibetan hulless barley genotypes: Z1141, a BLS-sensitive wild variety, and Kunlun14, a BLS-tolerant hybrid variety. A total of 36 conserved and 56 novel miRNAs were identified. Of these, 10 conserved and 10 novel miRNAs exhibited significantly changed expression between the normal and infected leaves of Kunlun14, respectively, while 3 conserved and 5 novel miRNAs exhibited significantly changed expression between the normal and infected leaves of Z1141, respectively. A total of 24 miRNAs were found in Z1141 and Kunlun14, and a further 546 putative target genes were predicted. Transcriptome sequencing analysis showed that among the 546 candidate genes, 131 had significant differences in expression between the normal and infected leaves of Kunlun14 and Z1141. Gene ontology, pathway, and Blast analyses indicated 10 candidate target genes that were involved in the barley disease resistance. These 10 candidate target genes may be regulated by 7 miRNAs. According to quantitative real-time PCR results, the 10 targets were negatively correlated with their corresponding miRNAs after infection with BLS. Conclusions The miRNAs and their target genes expressed in Tibetan hulless barley were identified and found to be associated with BLS resistance. Thus, these miRNAs and their target genes may be exploited via breeding programs or genetic engineering to improve BLS resistance in Tibetan hulless barley.

Characterization of barley germplasm for leaf stripe (Pyrenophora graminea) resistance based on incidence and severity parameters

Barley leaf stripe (BLS) caused by Pyrenophora graminea is an important seed-borne disease of barley causing significant yield and quality losses worldwide. The development of resistant cultivars has proven difficult, therefore, in this work, BLSresistant barley germplasm was developed by crossing six barley cultivars currently used in Europe and West Asia. Out of 270 doubled haploid lines derived from these crosses, 40 lines were evaluated under field artificial infection conditions using incidence (I; proportion of diseased plants) and severity (S; proportion of infected leaf area per plant). Disease resistance parameters showed a broad range of variation in mean I and S values with a continuum of resistance levels ranging from highly susceptible to highly resistant with values being consistently higher in the susceptible ones. However, eight promising resistant lines with high yield per plant were identified. Moreover, BLS severity increased linearly as incidence increased (r = 0.76, P < 0.001). This work suggests that BLS resistance sources identified in this study can be used for further genetic analysis and introgression for varietal improvement, and that the positive correlation between I and S parameters may be beneficial for many types of studies on this disease.

Genome Resource for Barley Leaf Stripe Pathogen Pyrenophora graminea

Pyrenophora graminea is the causative agent of barley leaf stripe disease. In this study, the strong pathogenic isolate QWC was used to generate DNA for Illumina sequencing. After assembly, its genome size was 42.5 Mb, consisting of 264 scaffolds, and a total of 10,376 genes was predicted. This is the first genome resource available for P. graminea. The genome sequences of P. graminea will accelerate the understanding interaction of P. graminea and barley.