Northwest A&F University
Xiaoguo Zhu, Zhensheng Kang
RNA interference (RNAi) is a powerful genetic tool to accelerate research in plant biotechnology and to control biotic stresses by manipulating target gene expression. However, the potential of RNAi in wheat to efficiently and durably control the devastating stripe rust fungus Puccinia striiformis f. sp. tritici (Pst), remained largely under explored, so far. To address this issue, we generated transgenic wheat lines expressing double-stranded RNA targeting PsFUZ7 transcripts of Pst. We analyzed expression of PsFUZ7 and related genes, and resistance traits of these transgenic wheat lines. We show that PsFUZ7 is an important pathogenicity factor that regulates infection and development of Pst. A PsFUZ7 RNAi construct stably expressed in two independent transgenic lines of wheat confers strong resistance to Pst. Pst hyphal development is strongly restricted, and necrosis of cells in plant resistance responses was induced significantly. We conclude that trafficking of RNA molecules from wheat plants to Pst may lead to a complex molecular dialogue between wheat and the rust pathogen. Moreover, we confirm the RNAi-based crop protection approaches can be used as a novel control strategy against rust pathogens in wheat.
CREA Research Centre for Genomics and Bioinformatics
,International Durum Wheat Genome Sequencing Consortium
The domestication of wild emmer wheat ~10,000 years ago by early agrarian societies have led to the selection of domesticated emmer and subsequently of durum wheat through a process of selection for non-brittle rachis and free-threshing forms. Durum wheat and became established as a prominent crop only ~1,500-2,000 years ago. We have completed the 10.45 Gb assembly of the 14 chromosomes of the modern DW cultivar 'Svevo' and provides, via comparison with the wild emmer assembly, an account of the genome-wide modifications imposed by 10,000 years of selection and breeding on the genome architecture of tetraploid wheat. A number of regions that were under selection during the domestication of wild emmer or the subsequent selection of durum wheat have been identified. Furthermore, we have projected on the durum wheat genome about 1,500 QTLs for morphological phenological and quality traits, grain yield components and disease resistance reported from published biparental mapping or GWAS. NBS-LRR genes are prominently involved in signaling and plant disease resistance. The durum wheat genome contains more than 66,000 genes and among them we annotated about 1,500 complete NBS-LRR genes. A similar number was found in the wild emmer genomes, nevertheless the comparison of the two genomes has identified some NBS-LRR genes specific for durum wheat. The availability of the complete genome of durum wheat will speed up the identification and the isolation of new resistance genes as well as the breeding for high-yielding and more resilient cultivars.
Dryland Agricultural Research Institute, Sararood branch, AREEO, Kermanshah, Iran
Ehsan,Lorestani, Reza, Haghparast, Mohammad Reza, Jalal Kamali, Ahmed, Amri, , , , , , , , , , , , , , , , , , , , , ,
Yellow rust (Puccinia striiformis Westendorf f. sp. tritici) is an important disease on wheat worldwide and especially in the highlands of West and Central Asia. Wheat landraces are composed of complex, variable, genetically dynamic and diverse populations, in equilibrium with both biotic and abiotic stresses prevailing in their environment. A germplasm collection consisting of 380 durum wheat accessions conserved at National Plant Gene Bank (Seed and Plant Improvement Institute, Iran) with worldwide origins, along with four check varieties were screened for resistance to yellow rust, and were also evaluated for several drought adaptative traits under rainfed conditions during 2009-10 cropping season at Sararood agricultural research station, Kermanshah, Iran. The study was conducted to quantify the phenotypic diversity and exploring durum accessions for yellow rust resistance, and to characterize the agronomic profile of different subsets of accessions for reaction to local yellow rust races. High natural infection, caused by the predominant virulent races of 6E8A+ and Yr27+, was experienced as shown by the 100 S reaction of the check bread wheat ?Sardari? and several highly susceptible accessions. The tested accessions exhibited significant variation in yellow rust severity, ranging from highly resistant to highly susceptible. Approximately 12.1% of accessions were found to be resistant to yellow rust, 9.5% were moderately resistant, 10.5% were moderately susceptible and 67.9% were susceptible. The germplasm showed a relatively modest response to yellow rust as expressed by a decrease in 1000-kernel weight (TKW) and a lower yield of the susceptible vs. resistant subsets by 11.4% and 19.9%, respectively. A comparison of foreign vs. Iranian resistant accessions, revealed higher yield productivity, higher TKW, and shorter plant height for the foreign accessions. Durum germplasm may constitute valuable genetic material for breeding new durum varieties characterized by high yield productivity under rainfed conditions and with adequate resistance to yellow rust.
Agricultural Biotechnology Research Institute, AARI, Faisalabad PAKISTAN
Shahid Nazir, Muhammad Waqas, Jamil Imran, Habib Muhammad, Zaffar Iqbal
Wheat is a major staple food in Pakistan and its production is subject to many yield limiting factors. Among biotic stresses, rusts have been the most devastating. Hence, the development of rust resistant genotype is the ultimate solution. The traditional approach of transferring resistant genes from wheat related species is time-consuming and laborious. It is complicated by the need to perform inoculation tests on plants in segregating populations, also requiring the application of appropriate races. Molecular markers could tag the presence of important resistance genes and allow breeders to identify the resistance genes rapidly and accurately. Therefore, use of molecular markers can help breeder in developing resistant wheat cultivars to minimize yield losses. To harvest the beauty of this system, 60 candidate wheat candidate varieties (included in provincial wheat yield trial) were screened against rusts using linked DNA markers for genes i.e. Lr-34/Yr-18, Lr-46/Yr-29, Lr-28, Lr-19, Sr-2 and Sr-32. Total genomic DNA was isolated and used as template in PCR for the verification of rust resistant genes. The gene Lr-34/Yr-18 was found present in one genotype and absent in 54 genotypes whereas one genotype was observed as heterozygote with respect to this gene. 49 candidate varieties for Lr-46/Yr-29, 03 for Lr-28, 56 for Lr-19, 38 for Sr-2 and 54 for Sr-32 were found positive showing presence of these genes in the new varieties. Missing entries were tested twice but no resistant gene(s) was detected. This information was shared with respective breeding institute to design the future research program. Furthermore, this molecular information was used for rust resistant gene pyramiding work to develop the durable resistance in wheat against rusts and crosses were attempted utilizing high yielding genotypes and genotypes carrying maximum rust resistance genes.
Northwest A&F University
Yanping,Fu, kang, Wang, Yingbin, Hao, Zhensheng, Kang, , , , , , , , , , , , , , , , , , , , , ,
Wheat adult plant resistance (APR) to stripe rust, a non-race-specific and durable resistance, is ideal for breeding. However, the knowledge concerning APR mechanism is largely limited. In order to further investigate the molecular basics of APR to provide guidance for wheat breeding, we conducted the transcriptome sequencing of wheat XZ9104 infected by Puccinia striiformis f. sp. tritici (Pst) at seeding and adult stages, respectively. Comparative analysis revealed that many WRKY transcription factors (TFs) may participate in the APR to stripe rust, of which, TaWRKY79 transcript levels were sharply elevated at the early infection stage in seedling plants. To dissect the relationship between TaWRKY79 and APR, we further studied the function of TaWRKY79. Subcellular localization showed that TaWRKY79 is located in the nuclear, and TaWRKY79 protein contains a separated region for mediating transcriptional activation at the C-terminus (246-328 aa) by yeast one-hybrid analysis. When TaWRKY79 was silenced by virus-induced gene silencing (VIGS) in seedling plants, the Pst growth was attenuated, with shortened hyphae, reduced hyphal branches and colony size. Meanwhile, the expression of TaWRKY79 was highly suppressed by salicylic acid (SA) but induced by jasmonic acid (JA) in seedling of wheat, and the transcription levels of LOX2 and PDF2.2 were significantly reduced, but the expression of PR1.1 was enhanced in TaWRKY79 knocking-down seedlings of wheat. Hence, these findings suggested that TaWRKY79, as a SA/JA cross talk, might play a negative role in resistance defence response to Pst infection at seeding stage by simultaneously activating the JA-dependent pathway and suppressing the SA-dependent pathway.
State Key Laboratory of Crop Stress Biology for Arid Areas and College of Life Sciences, Northwest A&F University, Yangling
Liyang Chen, Baoyu Huai, Shoujun Hu, Lijing Pang, Pu Yuan, Zhensheng Kang
Infection of pathogens in plants induces production and accumulation of reactive oxygen species (ROS). ROS are not only involved in plant defense responses, but directly restrict or kill pathogens. To counteract this attack, it is necessary for pathogens to remove host-produced ROS. However, the mechanisms protecting pathogens against host-derived oxidative stress are little known. In this study, a superoxide dismutase (SOD) gene, PsSOD2, was cloned from Puccinia striiformis f. sp. tritici (Pst). Quantitative reverse transcription PCR (qRT-PCR) analysis indicated that PsSOD2 is an in-planta induced gene active in the early stage of Pst infection. Prokaryotic expression and biochemical characterization revealed that PsSOD2 encoded a Cu-only SOD. The predicted signal peptide for protein secretion was functional in an invertase-mutated yeast strain. Transient expression in Nicotiana benthamiana suggested that PsSOD2 is localized in plasma membrane and dependent on glycophosphatidyl inositol (GPI) anchor at the C terminus. Furthermore, Size exclusion chromatography and bimolecular fluorescence complementation validated dimerization of PsSOD2. Overexpression of PsSOD2 in N. benthamiana significantly decreased ROS production triggered by flg22. Knockdown of PsSOD2 using a host-induced gene silencing (HIGS) system reduced the virulence of Pst, which was correlated to ROS accumulation in HIGS plants. These results suggest that PsSOD2 is a pivotal virulence factor that is localized in hyphal plasma membrane to promote Pst infection by scavenging host-derived ROS.
ICAR-IARI, New Delhi
Sudheer Kumar, Subhash Chandar Bhardwaj, Om Prakash Gangwar, Vaibhav Kumar Singh, Mukesh Kumar Pandey, Jaspal Kaur, Ashwani Kumar Basandrai, Deepshikha, Pradeep Singh Shekhawat, R.K. Devlash, V.K. Rathee
In India, wheat crop is a major contributor to the agricultural economy of India, occupying 30.7 mha area with 98.38 mt production. Stripe or yellow rust is a constraint to wheat production on about 12.0 m ha in the Northern Hills and North Western region of India. Varieties resistant at the time of release become susceptible usually within a few years due to new pathogen races. The present study conducted in 2015-16 was undertaken to identify stripe rust resistant genotypes among a set of 146 advanced breeding lines and popular cultivars. All genotypes were planted in two replications in northern India at ten locations viz., Karnal, Hisar (Haryana), Ludhiana, Gurdaspur (Punjab), Malan, Bajoura, Dhaulakuan (Himachal Pradesh), Pantnagar (Uttarakhand), Durgapura (Rajasthan), Jammu (J & K) and Delhi. After every 20 genotypes, infector (susceptible cultivar to both pathotypes) was planted. All genotypes were inoculated with mixture of prevalent Pst races 78S84 (Yr 27 virulence) and 46S119 (Yr 9 virulence) at Karnal. Out of 58 released cultivars grown in different zones of the country, fifteen lines (HS 507, DBW 90, HD 3086, WH 1080, WH 1124, WH 1142, HD 4728, HI 8498, HI 8737, MPO 1215 (D), NIDW 295 (d), UAS 428 (D), UAS 446 (D), DBW 71, KRL 210) showed stripe rust ACI < 10.00 (average coefficient of infection). But among advance 88 wheat lines, there was good level of resistance in 50 lines (ACI <10.00). Lines having AUDPC values <20% of those of the susceptible checks (maximum AUDPC value 2500 on susceptible check) were considered to be slow rusters. In present study, some of the wheat varieties (DBW 93, HS 490, PBW 723, PBW 644, VL 829, VL 892, WH 1105, WR 544 ) grown at present in northern India were identified as slow ruster lines. The information generated can be utilized in improving the stripe rust resistance of popular cultivars.
University of Bologna, Italy/ International Center for Agricultural Research in the Dry Areas, Morocco
Hafssa Kabbaj, khaoula El hassouni, Elisabetta Frascaroli, Angelo Petrozza, Stephan Summerer, Marco Maccaferri, Miguel Sanchez-Garcia, Roberto Tuberosa, Filippo M. Bassi
Global food security is faced with many threats including population growth and changing climate. To cope with these threats a new paradigm shift is required to ensure sufficient and sustainable crop production. Hybrid technology could represent a partly strategic solution for durum wheat, but the understanding of its heterotic behavior is very limited. In this study, 53 F1 plants were produced via half diallel scheme and North Carolina design II, using as parental elite lines selected on the basis of their genetic distance. These hybrids along with their parents were evaluated for different physiological and root traits on a precision phenotyping platform (Lemnatec) at different levels of water stress. Additionally, a second root test was conducted in near field condition via a basket method to determine shallow or deep rooting behavior. Hybrids with the most heterotic combinations in terms of above and below ground biomass were identified. However, in order to ensure adequate pollination between heterotic parents, their flowering time must overlap. To identify good matching partners, a GWAS study was conducted to identify genomic regions associated with the control of flowering time in durum wheat. A total of 384 landraces and modern germplasm were assessed at 13 environments with different temperatures and day length throughout the season. Genotyping was conducted by 35K Axiom array to generate 8,173 polymorphic SNPs. In total, 12 significant QTLS for landraces and 17 QTLs for modern germplasm were identified consistently across environments. These two results when combined will allow to predict the best parental partners for hybrid production via markers screening on the basis of their genetic similarity to the most heterotic groups, and with matching flowering times.
ICAR-Indian Institute of Wheat and Barley Research, Karnal
Satish Kumar, Ratan Tiwari, Gyanendra Pratap Singh
Stripe rust, is a major constraint to wheat production in the more than 12.8 m ha region of the Northern Hills and North Western Plains zones in India. The previously deployed resistance genes Yr9 and Yr27 are no longer effective. New sources of resistance (Yr5, Yr10, Yr15, Yr24) became available under the umbrella of an Indo-Australian collaborative project. A set of advanced backcross derivative lines out yielded the checks in preliminary evaluations and were promoted to station-level (16 lines) and national (5 lines) trials. A new cohort of resistance genes (Yr47, Yr51, Yr57) are now available and are being used in the breeding program. Resistance genes Yr17, Yr18, Yr31, Yr36, Yr40, Yr53, YrC591, and Yr70 are also being used. The recent progress in development of high yielding, stripe rust resistant lines will help to address future threats from stripe rust.
Institute of Agricultural Sciences, Banaras Hindu University, Varanasi 221005, India
Punam Singh Yadav, Ramesh Chand, Vinod Kumar Mishra, Uttam Kumar, Arun Kumar Joshi
The Sr2 gene has been used extensively in bread wheat improvement for durable stem rust resistance. Interestingly, the resistance of Sr2, associated with the pleotrophic gene Pbc expressed as pseudo-black chaff (PBC), is tightly linked with Yr30/Lr27/Pm genes conferring multiple disease resistance. The linkage map of chromosome 3BS revealed that Sr2 is 0.43cM away from lesion mimic (lm) locus. The RIL population (Yangmai#6 ? Sonalika) of 88 lines including parents where Sonalika carries Sr2 and lm while Yangmai#6 is deficient to both was evaluated for three years (2013-2016). The objective was to determine if this fragment is inherited as one unit and provides resistance to multiple diseases. Twenty four SSR markers distributed between 0.00 to 7.09cM on 3BS covering both Sr2 (5.57cM) and lm locus (6.0cM) were studied in the RIL population. Phenotyping was done for Sr2 associated PBC and lesion mimic along with disease severity for leaf rust, and spot blotch. Positive and significant correlations were observed between leaf stem rust resistance with Sr2 carrying PBC and lm. However, lines with lm either alone or with Sr2 (showing PBC) exhibited spot blotch susceptibility. The reverse situation does not hold not true where genotypes carrying Sr2 alone showed no correlation with spot blotch resistance. This indicates that the Sr2 complex is inherited as a single unit. Use of 24 SSR also suggest that Sr2 and lm loci are tightly linked and inherited together. The co-inheritance of Sr2 and lm ensures the stability and durability of rust resistance. However, the discouraging observation of spot blotch susceptibility due to lm gene suggests a limitation in achieving multiple disease resistance in environments where spot blotch is important. We identified two transgressive segregates in the population showing least expression of lm despite the presence of Sr2 and lm together.