Race and Virulence Dynamics of Puccinia triticina in China During 2007 to 2021.

The challenge of wheat leaf rust on wheat production is a recurring issue. Race identification of Puccinia triticina (Pt) serves as the foundation for preventing and controlling this disease. In a 15-year study, we identified 2,900 isolates of Pt from 20 provinces, cities, or autonomous regions in China during 2007 to 2021 and found 332 virulence phenotypes with 11 predominant phenotypes: PHT (8.3%), THT (5.4%), PHK (4.5%), PHJ (3.7%), THJ (3.6%), SHJ (3.5%), THS (3.3%), FGD (2.9%), THK (2.6%), PHS (2.4%), and PHD (2.0%). The virulence frequency for 40 Lr genes was identified across different years and areas; one major reason for the race dynamics was the attenuation to Lr1 and Lr26, which was more evident in southwest China. Lr9, Lr24, Lr28, Lr38, and Lr42 maintained effectiveness in China, while Lr2c, Lr10, Lr12, Lr14a, Lr14b, Lr22a, Lr33, and Lr36 nearly lost their effectiveness against wheat leaf rust disease. No significant difference was found among predominant phenotypes in different areas (P > 0.1). However, 12 Lr sites were found to have differences in virulence frequencies with values greater than 20% across various locations; furthermore, the lowest and highest virulence values were observed in north China (Area 1) and northwest China (Area 5), respectively. According to phenotype dynamics, PHT, THT, FGD, THK, and PHS are more likely to persist over time. In addition, much attention should be given toward discovering rising combinations of virulent phenotypes.

Dynamics of Carbendazim-Resistance Frequency of Pathogens Associated with the Epidemic of Fusarium Head Blight.

Carbendazim resistance was detected using 4,701 Fusarium graminearum species complex isolates collected from major wheat-producing regions in China from 2018 to 2020. A total of 348 carbendazim-resistant isolates were identified. The majority of carbendazim-resistant isolates were detected in Jiangsu and Anhui Provinces. In total, 227 and 88 isolates were obtained from each of the Jiangsu and Anhui Provinces, with a high resistance frequency of 41.12 and 20.56%, respectively. The predominant resistant isolates harboring point mutations were F167Y (79.31%), followed by E198Q (16.38%) and F200Y (4.31%). Compared with F. graminearum, F. asiaticum isolates were more likely to produce carbendazim resistance. In this study, we first detected carbendazim-resistant isolates in Hebei, Shaanxi, Sichuan, and Hunan Provinces. In Jiangsu, Anhui, and Zhejiang, the frequency of carbendazim-resistant isolates maintained a high level, resulting in stable carbendazim-resistant populations. We also found the dynamic of carbendazim-resistance frequency in most provinces showed similar trends to the epidemic of Fusarium Head Blight (FHB). Our results facilitate the understanding of the current situation of carbendazim resistance of FHB pathogens and will be helpful for fungicides selection in different wheat-producing areas in China.

Long-Distance Transport of Puccinia striiformis f. sp. tritici by Upper Airflow on the Yunnan-Guizhou Plateau Disrupts the Balance of Agricultural Ecology in Central China.

Long-distance dispersal of plant pathogens in the air can establish diseases in other areas and lead to an increased risk of large-scale epidemics. Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most destructive diseases of wheat in China. Hubei is an important overwintering region for Pst in China, and this overwintering region is a determinant of stripe rust severity in eastern China. In 2017, stripe rust disease caused a pandemic in the Hubei region and resulted in great yield losses of wheat. To explain the disease pandemic, a total of 595 single-lesion samples of stripe rust were collected in spring, including 204 in five provinces in 2017 and 391 in four provinces in 2018, and genotyped with 13 simple sequence repeat makers. The samples were classified into 12 subpopulations based on the locations and year of collection. Genetic diversity was determined for the collection and each subpopulation. Differentiation and gene flow were determined between subpopulations. STRUCTURE analyses and discriminant analysis of principal components were conducted, and the results were used to infer the relationships between subpopulations. Our study revealed a new route of Pst transmission from the Yunnan-Guizhou Plateau to the Hubei region. The Pst inoculum of northwestern Hubei came from Gansu in the northwest, whereas the inoculum in southern Hubei came from the Yunnan-Guizhou Plateau via upper airflow. After the initial inocula infected wheat plants and multiplied in northern and southern Hubei, urediniospores produced in these regions further spread together along the middle reach of Hanshui Valley and made exchanges there. The finding of the new transmission route of Pst is important for improving integrated stripe rust disease management, which should have a profound impact on the balance of agricultural ecology in China.

Current Status and Future Perspectives of Genomics Research in the Rust Fungi.

Rust fungi in Pucciniales have caused destructive plant epidemics, have become more aggressive with new virulence, rapidly adapt to new environments, and continually threaten global agriculture. With the rapid advancement of genome sequencing technologies and data analysis tools, genomics research on many of the devastating rust fungi has generated unprecedented insights into various aspects of rust biology. In this review, we first present a summary of the main findings in the genomics of rust fungi related to variations in genome size and gene composition between and within species. Then we show how the genomics of rust fungi has promoted our understanding of the pathogen virulence and population dynamics. Even with great progress, many questions still need to be answered. Therefore, we introduce important perspectives with emphasis on the genome evolution and host adaptation of rust fungi. We believe that the comparative genomics and population genomics of rust fungi will provide a further understanding of the rapid evolution of virulence and will contribute to monitoring the population dynamics for disease management.

Characterization of histological changes at the tillering stage (Z21) in resistant and susceptible wheat plants infected by Tilletia controversa Kühn.

BACKGROUND: Dwarf bunt, which is caused by Tilletia controversa Kühn, is a soilborne and seedborne disease that occurs worldwide and can lead to 70% or even total losses of wheat crops. However, very little information is available about the histological changes that occur in dwarf bunt-resistant and dwarf bunt-susceptible wheat plants at the tillering stage (Z21). In this study, we used scanning electron microscopy and transmission electron microscopy to characterize the histological changes at this stage in resistant and susceptible wheat cultivars infected by T. controversa. RESULTS: Using scanning electron microscopy, the root, stem, and leaf structures of resistant and susceptible cultivars were examined after T. controversa infection. The root epidermal and vascular bundles were more severely damaged in the susceptible T. controversa-infected plants than in the resistant plants. The stem cell and longitudinal sections were much more extensively affected in susceptible plants than in resistant plants after pathogen infection. However, slightly deformed mesophyll cells were observed in the leaves of susceptible plants. With transmission electron microscopy, we found that the cortical bundle cells and the cell contents and nuclei in the roots were more severely affected in the susceptible plants than in the resistant plants; in the stems and leaves, the nuclei, chloroplasts, and mesophyll cells changed significantly in the susceptible plants after fungal infection. Moreover, we found that infected susceptible and resistant plants were affected much more severely at the tillering stage (Z21) than at the seedling growth stage (Z13). CONCLUSION: Histological changes in the wheat roots, stems and leaves were much more severe in T. controversa-infected susceptible plants than in infected resistant plants at the tillering stage (Z21).

Effects of Tilletia foetida on Microbial Communities in the Rhizosphere Soil of Wheat Seeds Coated with Different Concentrations of Jianzhuang.

Tilletia foetida (syn. T. laevis) leads to wheat common bunt, a worldwide disease that can lead to 80% yield loss and even total loss of production, together with degrading the quality of grains and flour by producing a rotten fish smell. To explore the potential microbial community that may contribute to the control of soil- and seed-borne pathogens, in this study, we analyzed the effects of the plant pathogenic fungus T. foetida on rhizosphere soil microorganisms in wheat seeds coated with different concentrations of a fungicide (Jianzhuang) used to control the disease. To analyze the bacterial and fungal abundance in T. foetida-infected and mock-infected plants, the microorganisms were sequenced using high-throughput HiSeq 2500 gene sequencing. The results showed that bacterial communities, including Verrucomicrobia, Patescibacteria, Armatimonadetes, Nitrospirae, Fibrobacteres, Chlamydiae, and Hydrogenedentes, and fungal communities, including Basidiomycota and Ciliophora, were more prevalent in the mock group than in the T. foetida-infected group, which may contribute to the control of wheat common bunt. Moreover, cluster and PCoA analysis revealed that replicates of the same samples were clustered together, and these results were also found in the distance index within-group analysis for bacterial and fungal communities in the T. foetida-infected and mock groups.

Analyses of Wheat Yellow Rust Populations Reveal Sexual Recombination and Seasonal Migration Pattern of Puccinia striiformis f. sp. tritici in Gangu, Northwestern China.

Puccinia striiformis f. sp. tritici is the causal agent of wheat yellow rust with records of regular and severe epidemics in China. This study explored the population dynamics of the yellow rust pathogen in Gangu, northwestern China. In Gangu, the Weihe River runs from west to east and divides Gangu into three regions: North and South mountain, with the valley in between. To study the genetic structure of the pathogen in local populations, samples were collected over 3 years from the three regions at different altitudes both within and between the wheat cropping seasons. A total of 811 P. striiformis f. sp. tritici isolates were successfully genotyped using 16 simple sequence repeat markers. The results suggest that P. striiformis f. sp. tritici can survive year-round in Gangu. The P. striiformis f. sp. tritici populations migrated among the regions, and the migration pattern was not related to altitude. The oversummering populations in the North and South mountain regions were genetically different from each other; and the P. striiformis f. sp. tritici populations collected from the lower altitude in the valley had no relationship with any of the populations collected in the spring or fall, indicating that they too have a different origin. Signatures of random mating were found in the populations collected in both North and South mountain regions, but not in the valley populations.

Phylogenomic Analysis of a 55.1-kb 19-Gene Dataset Resolves a Monophyletic Fusarium that Includes the Fusarium solani Species Complex.

Scientific communication is facilitated by a data-driven, scientifically sound taxonomy that considers the end-user's needs and established successful practice. In 2013, the Fusarium community voiced near unanimous support for a concept of Fusarium that represented a clade comprising all agriculturally and clinically important Fusarium species, including the F. solani species complex (FSSC). Subsequently, this concept was challenged in 2015 by one research group who proposed dividing the genus Fusarium into seven genera, including the FSSC described as members of the genus Neocosmospora, with subsequent justification in 2018 based on claims that the 2013 concept of Fusarium is polyphyletic. Here, we test this claim and provide a phylogeny based on exonic nucleotide sequences of 19 orthologous protein-coding genes that strongly support the monophyly of Fusarium including the FSSC. We reassert the practical and scientific argument in support of a genus Fusarium that includes the FSSC and several other basal lineages, consistent with the longstanding use of this name among plant pathologists, medical mycologists, quarantine officials, regulatory agencies, students, and researchers with a stake in its taxonomy. In recognition of this monophyly, 40 species described as genus Neocosmospora were recombined in genus Fusarium, and nine others were renamed Fusarium. Here the global Fusarium community voices strong support for the inclusion of the FSSC in Fusarium, as it remains the best scientific, nomenclatural, and practical taxonomic option available.

Contamination and Translocation of Deoxynivalenol and Its Derivatives Associated with Fusarium Crown Rot of Wheat in Northern China.

Fusarium crown rot (FCR) is one of the most important wheat diseases in northern China. The main causal agent of FCR, Fusarium pseudograminearum, can produce mycotoxins such as type B trichothecenes. Therefore, FCR could be an additional source of mycotoxin contamination during wheat production. Field inoculation experiments demonstrated that FCR disease severity strongly impacts the distribution pattern of trichothecenes in different wheat tissues. Mycotoxins were mainly observed in lower internodes, and a low amount was detected in the upper parts above the fourth internode. However, high levels of trichothecene accumulation were detected in the upper segments of wheat plants under field conditions, which would threaten the feed production. The variation of mycotoxin content among sampling sites indicated that besides disease severity, other factors like climate, irrigation, and fungicide application may influence the mycotoxin accumulation in wheat. A comprehensive survey of deoxynivalenol (DON) and its derivatives in wheat heads with FCR symptoms in natural fields was conducted at 80 sites in seven provinces in northern China. Much higher levels of mycotoxin were observed compared with inoculation experiments. The mycotoxin content varied greatly among sampling sites, but no significant differences were observed if compared at province level, which indicated the variation is mainly caused by local conditions. Trace amounts of mycotoxin appeared to be translocated to grains, which revealed that FCR infection in natural fields poses a relatively small threat to contamination of grains but a larger one to plant parts that may be used as animal feed. To our knowledge, this is the first report of trichothecene accumulation in wheat stems and heads, as well as grains after FCR infection in natural field conditions. These investigations provide novel insights into food and feed safety risk caused by FCR in northern China.

Identification and Cloning of a CC-NBS-NBS-LRR Gene as a Candidate of Pm40 by Integrated Analysis of Both the Available Transcriptional Data and Published Linkage Mapping.

Wheat powdery mildew, caused by the obligate parasite Blumeria graminis f. sp. tritici, severely reduces wheat yields. Identifying durable and effective genes against wheat powdery mildew and further transferring them into wheat cultivars is important for finally controlling this disease in wheat production. Pm40 has been widely used in wheat breeding programs in Southwest China due to the spectrum and potentially durable resistance to powdery mildew. In the present study, a resistance test demonstrated that Pm40 is still effective against the Bgt race E20. We identified and cloned the TraesCS7B01G164000 with a total length of 4883 bp, including three exons and two introns, and encoded a protein carrying the CC-NBS-NBS-LRR domain in the Pm40-linked region flanked by two EST markers, BF478514 and BF291338, by integrating analysis of gene annotation in wheat reference genome and both sequence and expression difference in available transcriptome data. Two missense mutations were detected at positions 68 and 83 in the CC domain. The results of both cosegregation linkage analysis and qRT-PCR also suggested that TraesCS7B01G164000 was a potential candidate gene of Pm40. This study allowed us to move toward the final successfully clone and apply Pm40 in wheat resistance improvement by gene engineering.

First Report of Wheat Common Bunt Caused by Tilletia laevis in Henan Province, China.

Wheat common bunt is a serious disease that may lead to yield losses of 75-80% in many wheat regions of the world (Mathre 1996). The disease may reduce yield and flour quality by producing trimethylamine, a compound that smells like rotting fish (Castlebury et al. 2005; Hoffmann 1981; Mathre 1996). Two closely related basidiomycete species, Tilletia caries (DC.) Tul. & C. Tul. [syn. T. tritici (Bjerk.) Wint.] and T. laevis J. G. Kühn [syn. T. foetida (Wallr.) Liro], cause wheat common bunt. Teliospore morphology is used to differentiate the two species. Teliospores of T. caries have reticulates on the surface while teliospores of T. laevis have a smooth surface (Pieczul et al. 2018). T. laevis was reported in Liaoning, Shaanxi, Shandong, Beijing, Hebei, Shanxi, Jilin, Heilongjiang, Jiangsu, Gansu, Xinjiang, Sichuan, Yunnan, Inner Mongolia, and Tibet (Guo 2011; Wang 1963), but not in Henan, the biggest wheat production province in China, before the present study. In July 2019, we found wheat common bunt in three fields grown with cultivar Zhengmai 618 in Yugong Mountain, Henan province. The diseased wheat heads had bunt balls filled with black powder with fishy smell. The disease incidences in these fields were 20-50%, but no common bunt was found in other nearby fields. About 200 diseased heads were sampled from the three fields. Teliospores from each head were observed under a microscope, and they all had smooth surface. Observations using a scanning electron microscope also showed smooth-surfaced teliospores. Teliospores were measured 13.5 to 18.5 µm in diameter. After surface sterilization of diseased heads using 0.25% NaClO for 5 min, teliospore suspension (1×106/ml) was made using sterilized distilled water and spread on water agar (200 µl per plate), and the plates were kept at 15°C with 24 h light (Goates and Hoffman 1987). On the 6th days, teliospores were germinated. Based on the disease symptoms, teliospore morphology, and germination, the bunt fungus was identified as T. laevis. To fulfill Koch's postulates, 1 ml of germinating teliospore suspension at the concentration of 106 spores/ml was injected into the heads of susceptible wheat cultivar (Dongxuan 3) at the boot stage with a syringe, and the plants injected with sterile ddH2O were used as control. The inoculated plants were grown in a growth chamber at 17°C with 50% humidity and 24 h light (300 µmol/m2/s). After one month at the ripening stage, the kernels of the inoculated plants were filled with black teliospores releasing fishy smell, and the control plants did not have bunt heads. Under a scanning electron microscope, teliospores from the inoculated heads had smooth surface and were measured 13.5 to 18.5 µm in diameter, similar to the teliospores of bunt heads from the fields. The fungus was also confirmed through molecular characterization using sequence characterized amplification region (SCAR) markers specific for T. laevis, and the expected 660 bp (Yao et al., 2019) and 286 bp (Zhang et al. 2012) bands were obtained separately from the teliospore samples from both the fields and growth chamber. The collection named as CGMCC 3.20112 was deposited in China General Microbiological Culture Collection Center. To the best of our knowledge, this is the first report of T. laevis causing wheat common bunt in Henan Province of China. Because the pathogen is seedborne and soilborne, the disease may become a high risk to wheat production in Henan and other provinces of China.

iTRAQ-Based Proteomic Analysis of Wheat Bunt Fungi Tilletia controversa, T. caries, and T. foetida.

This is the first study of proteomics of wheat bunt fungi Tilletia controversa (TCK), T. caries (TCT), and T. foetida (TFL) using the iTRAQ technique. Based on the relative quantities of specific proteins between each two pathogens, we found 50 up-regulated and 80 down-regulated protein genes in TCK compared to TFL, 62 up-regulated and 82 down-regulated protein genes in TCT compared to TFL, 47 up-regulated and 30 down-regulated protein genes in TCK compared to TCT, and there were 1 protein of up-regulated and 4 proteins of down-regulated in the three pairs. These protein data could be of great value for exploring the key proteins which play an important role in the interactions of these pathogens with their host. Some of them could be valuable for differentiating the three pathogens with monoclonal antibodies produced by the specific proteins and may enable in-site detection of the pathogens and performing routine monitoring as a diagnostic assay in wheat shipments.

Transcriptome Analysis Identifies a 140 kb Region of Chromosome 3B Containing Genes Specific to Fusarium Head Blight Resistance in Wheat.

Fusarium head blight (FHB), mainly caused by Fusarium graminearum, is one of the most destructive fungal diseases of wheat (Triticum aestivum L.). Because of the quantitative nature of FHB resistance, its mechanism is poorly understood. We conducted a comparative transcriptome analysis to identify genes that are differentially expressed in FHB-resistant and FHB-susceptible wheat lines grown under field conditions for various periods after F. graminearum infection and determined the chromosomal distribution of the differentially expressed genes (DEGs). For each line, the expression in the spike (which exhibits symptoms in the infected plants) was compared with that in the flag leaves (which do not exhibit symptoms in the infected plants). We identified an island of 53 constitutive DEGs in a 140 kb region with high homology to the FhbL693b region on chromosome 3B. Of these genes, 13 were assigned to specific chloroplast-related pathways. Furthermore, one gene encoded inositol monophosphate (IMPa) and two genes encoded ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO). Our findings suggest that the temporary susceptibility in locally infected spikes results from the cross-talk between RuBisCO and IMPa, which blocks secondary signaling pathways mediated by salicylic acid and induces a systemic acquired resistance in the distant leaf tissue.

Wheat Resistance to Fusarium Head Blight is Associated With Changes in Photosynthetic Parameters.

Fusarium head blight (FHB) is an important wheat disease worldwide; however, its effects on the physiological parameters in plants with different levels of FHB resistance remain unclear. Here, we evaluated the effects of Fusarium graminearum infection on yield and the photosynthesis-associated parameters Pn, Gs, and Ci of wheat flag leaves and determined the influence of FHB resistance. The FHB-resistant wheat genotype L699 and its susceptible sister line L661 were point- and spray-inoculated. Photosynthesis-associated parameters were subsequently measured using a modulated photosynthesis system, and FHB intensity was evaluated. Compared with L661, FHB caused more significant reductions in the net photosynthetic rate and stomatal conductance of flag leaves in L699. However, FHB caused a larger reduction in the 1000-grain weight and total grain weight per spike in L661 compared with L699. Independence sample t test showed that FHB resistance was significantly higher in L699 compared with L661. We concluded that under the conditions of the present study, FHB had a significantly greater effect on net photosynthesis in the resistant line compared with the susceptible line; however, it had a greater impact on yield components in the susceptible line. These results provide a new insight into the physiological cost of host resistance to FHB.

Wheat WCBP1 encodes a putative copper-binding protein involved in stripe rust resistance and inhibition of leaf senescence.

BACKGROUND: Stripe rust, a highly destructive foliar disease of wheat (Triticum aestivum), causes severe losses, which may be accompanied by reduced photosynthetic activity and accelerated leaf senescence. METHODS: We used suppression subtractive hybridization (SSH) to examine the mechanisms of resistance in the resistant wheat line L693 (Reg. No. GP-972, PI 672538), which was derived from a lineage that includes a wide cross between common and Thinopyrum intermedium. Sequencing of an SSH cDNA library identified 112 expressed sequence tags. RESULTS: In silico mapping placed one of these tags [GenBank: JK972238] on chromosome 1A. Primers based on [GenBank: JK972238] amplified a polymorphic band, which co-segregated with YrL693. We cloned a candidate gene encoding wheat copper-binding protein (WCBP1) by amplifying the polymorphic region, and we mapped WCBP1 to a 0.64 cM genetic interval. Brachypodium, rice, and sorghum have genes and genomic regions syntenic to this region. DISCUSSION: Sequence analysis suggested that the resistant WCBP1 allele might have resulted from a deletion of 36-bp sequence of the wheat genomic sequence, rather than direct transfer from Th. intermedium. qRT-PCR confirmed that WCBP1 expression changes in response to pathogen infection. CONCLUSIONS: The unique chromosomal location and expression mode of WCBP1 suggested that WCBP1 is the putative candidate gene of YrL693, which was involved in leaf senescence and photosynthesis related to plant responses to stripe rust infection during the grain-filling stage.

Development of a SCAR marker for molecular detection and diagnosis of Tilletia controversa Kühn, the causal fungus of wheat dwarf bunt.

Tilletia controversa Kühn (TCK) is an important quarantine pathogen that causes wheat dwarf bunt and results in devastating damage to wheat production. The fungus is difficult to be distinguished from T. caries and T. laevis, which cause wheat common bunt, based on morphological, physiological and symptomatological characteristics of the pathogens. The traditional detection of the fungus can be a long and tedious process with poor accuracy. The inter-simple sequence repeat (ISSR) technique has been used for identifying molecular markers for detection of TCK. Of 28 ISSR primers screened, ISSR-859 amplified a specific 678 bp DNA fragment from all TCK isolates but not from any isolates of the common bunt fungi or other pathogenic fungi tested. Based on the fragment sequence, a pair of sequence characterized amplified region (SCAR) primers was designed, which amplified a 372 bp DNA fragment specifically in TCK. The SCAR marker was detected using as low as 1 ng template DNA of TCK, and was also detected using broken teliospores and DNA from asymptomatic wheat samples. We developed the SYBR Green I and TaqMan Green I and TaqMan real-time polymorphism chain reaction methods to detect TCK with the detection limit of 0.1 fg with asymptomatic wheat samples. Further work is needed to develop a rapid test kit for this pathogenic fungus using the designed specific primers.

Characterization of a Small Cysteine-Rich Secreted Effector, TcSCP_9014, in Tilletia controversa.

Tilletia controversa J. G. Kühn is the causal agent of wheat dwarf bunt (DB), a destructive disease causing tremendous economic losses. Small cysteine-rich secreted proteins (SCPs) of plant fungi are crucial in modulating host immunity and promoting infection. Little is known about the virulence effectors of T. controversa. Here, we characterized TcSCP_9014, a novel effector of SCPs, in T. controversa which suppressed programmed cell death triggered by BAX without relying on its signal peptide (SP). The SP in the N-terminus of TcSCP_9014 was functional in the secretory process. Live-cell imaging in the epidermal cells of Nicothiana benthamiana suggested that TcSCP_9014 localized to the plasma membrane, cytoplasm, and nucleus. Furthermore, yeast cDNA library screening was performed to obtain the interacting proteins in wheat. Yeast two-hybrid and BiFC assays were applied to validate the interaction of TcSCP_9014 with TaMTAN and TaGAPDH. Our work revealed that the novel effector TcSCP_9014 is vital in modulating plant immunity, which opens up new avenues for plant-pathogen interactions in the T. controversa infection process.

Microbiome Signature of Endophytes in Wheat Seed Response to Wheat Dwarf Bunt Caused by Tilletia controversa Kühn.

Wheat dwarf bunt leads to the replacement of seeds with fungal galls containing millions of teliospores of the pathogen Tilletia controversa Kühn. As one of the most devastating internationally quarantined wheat diseases, wheat dwarf bunt spreads to cause distant outbreaks by seeds containing teliospores. In this study, based on a combination of amplicon sequencing and isolation approaches, we analyzed the seed microbiome signatures of endophytes between resistant and susceptible cultivars after infection with T. controversa. Among 310 bacterial species obtained only by amplicon sequencing and 51 species obtained only by isolation, we found 14 overlapping species by both methods; we detected 128 fungal species only by amplicon sequencing, 56 only by isolation, and 5 species by both methods. The results indicated that resistant uninfected cultivars hosted endophytic communities that were much more stable and beneficial to plant health than those in susceptible infected cultivars. The susceptible group showed higher diversity than the resistant group, the infected group showed more diversity than the uninfected group, and the microbial communities in seeds were related to infection or resistance to the pathogen. Some antagonistic microbes significantly suppressed the germination rate of the pathogen's teliospores, providing clues for future studies aimed at developing strategies against wheat dwarf bunt. Collectively, this research advances the understanding of the microbial assembly of wheat seeds upon exposure to fungal pathogen (T. controversa) infection. IMPORTANCE This is the first study on the microbiome signature of endophytes in wheat seed response to wheat dwarf bunt caused by Tilletia controversa Kühn. Some antagonistic microbes suppressed the germination of teliospores of the pathogen significantly, which will provide clues for future studies against wheat dwarf bunt. Collectively, this research first advances the understanding of the microbial assembly of wheat seed upon exposure to the fungal pathogen (T. controversa) infection.

Intelligent reprogramming of wheat for enhancement of fungal and nematode disease resistance using advanced molecular techniques.

Wheat (Triticum aestivum L.) diseases are major factors responsible for substantial yield losses worldwide, which affect global food security. For a long time, plant breeders have been struggling to improve wheat resistance against major diseases by selection and conventional breeding techniques. Therefore, this review was conducted to shed light on various gaps in the available literature and to reveal the most promising criteria for disease resistance in wheat. However, novel techniques for molecular breeding in the past few decades have been very fruitful for developing broad-spectrum disease resistance and other important traits in wheat. Many types of molecular markers such as SCAR, RAPD, SSR, SSLP, RFLP, SNP, and DArT, etc., have been reported for resistance against wheat pathogens. This article summarizes various insightful molecular markers involved in wheat improvement for resistance to major diseases through diverse breeding programs. Moreover, this review highlights the applications of marker assisted selection (MAS), quantitative trait loci (QTL), genome wide association studies (GWAS) and the CRISPR/Cas-9 system for developing disease resistance against most important wheat diseases. We also reviewed all reported mapped QTLs for bunts, rusts, smuts, and nematode diseases of wheat. Furthermore, we have also proposed how the CRISPR/Cas-9 system and GWAS can assist breeders in the future for the genetic improvement of wheat. If these molecular approaches are used successfully in the future, they can be a significant step toward expanding food production in wheat crops.

Race Composition of Puccinia striiformis f. sp. tritici in Tibet, China.

In Tibet, China, wheat stripe rust (caused by Puccinia striiformis f. sp. tritici) has recently become one of the most destructive diseases on winter wheat. To identify races of the pathogen in Tibet, 261 isolates were obtained in 2010 and tested on seedlings of a standard set of 19 wheat indicator genotypes. Of the 261 isolates, 248 were identified as members of 19 known races (CYR17, CYR20, CYR21, CYR22, CYR23, CYR29, CYR31, CYR32, CYR33, Lov13-6, Su11-1, Su11-2, Su11-3, Su11-4, Su11-5, Su11-6, Su11-7, Su11-8, and Su11-13), and 13 identified as representatives of 4 new races. CYR32 and CYR33 were the most predominant. The number of races and their frequencies in Tibet were more similar to the fungal populations in Sichuan and Gansu provinces than to those in Yunnan, Qinghai, and Shaanxi provinces. The results suggest that Tibet is also a possible center of inoculum source and genetic variation for the stripe rust pathogen in addition to Sichuan and Gansu.