The University of Jordan
Ayed Al Abdallat, Monther Tahat
Studies on whet stem rust (WSR) in Jordan are considered to be old. There was only one study conducted in the late 1980's by Abu-Blan and Duwayri (1989) to evaluate the infection of wheat cultivars with black stem rust disease (Puccinia graminis f. sp. tritici). Recently, reports of stem rust were published in Israel and Lebanon in 2010 and first report of Ug99 was reported in Egypt in 2014. The objectives of our research are to: (i) survey wheat growing areas for WSR in Jordan during the years 2017-2020, (ii) identification of WSR races isolated from Jordan morphologically and molecularly, (iii) analyze rust populations in terms of their response to known differential sets, pathotype distribution and diversity, (iv) screening the response of Jordanian wheat germplasm to the identified WSR strains, and (vi) study the population diversity of WSR races using RT-PCR and SNP genotyping. In 2017 a total of 270 fields of wheat and barley in the wheat and barley growing areas in Jordan were surveyed from March-May. The survey covered northern, middle, and southern parts of Jordan (arid and semi-arid regions). Altitude, longitude, and latitude data was recorded. Only few WSR pustules (n=4) were collected because the environmental conditions were not suitable for the disease to develop. On the other hand, wheat stripe rust was very common in the wheat growing areas mainly at the southern parts of the country. Other fungal plant pathogens were also reported including smuts, spots, blotches, powdery mildew, crown rot, fusarium head blight, and flag smut.
Leonardo,Crespo-Hererra, Julio, Huerta, Ravi, Singh, , , , , , , , , , , , , , , , , , , , , , , ,
Malnutrition affects more than 2 billion people across the globe, particularly zinc and iron deficiency causes major health problem in developing world. The biofortified staple food crops such as wheat, is an important channel to contribute to the hidden hunger problem in low income countries. Breeding for enhanced zinc concentration in wheat was initiated by crossing high zinc sources identified among synthetic wheats, T. dicoccum, T. spelta and landraces. These crosses have resulted in wheat varieties with competitive yields and enhanced grain zinc were adapted by farmers in South Asia. CIMMYT-derived early-maturity wheat cultivar 'Zinc-Shakti' with about 40% increased zinc (+14 ppm), is now grown in eastern India through public-private partners. The two CIMMYT-derived biofortified varieties: 'WB2' and 'HPBW01' released in 2016 for northwestern plains zone of India. In Pakistan, 'Zincol' was released in 2016. The first high zinc wheat variety (Bari-Gom 33) with better resistance to wheat blast have been released in Bangladesh for commercial cultivation in 2017. Targeted crosses with increased population sizes were used to obtain superior progeny lines that have high zinc levels in combination with other essential traits. This has resulted in the incorporation of several novel alleles for grain zinc and iron in elite, high-yielding germplasm. High zinc and iron are under quantitative genetic control and further progress is possible as multiple QTL are pyramided in high yielding wheats. High-throughput, non-destructive phenotyping for grain zinc and iron using the X-ray fluorescence (XRF) analysis has facilitated the selection dramatically. Gene discovery and mapping studies leading to the utilization of markers to further improve the breeding efficiency. Rapid adoption of high zinc wheat varieties in South Asia and beyond is expected with the second wave of high zinc wheat lines with superior yield, heat and drought tolerance and resistance to rusts and other foliar diseases.
University of Georgia
Mohamed,Mergoum, Yuanfeng, Hao, Jerry, Johnson, Dan, Bland, James, Buck, John, Youmans, Benzamin, Lopez, Steve, Sutton, Zhenbang, Chen, , , , , , , , , , , ,
Leaf rust disease, caused by the fungal pathogen Puccinia tritcina, is the most destructive foliar disease of wheat worldwide. Gene combination of Lr37/Yr17/Sr38 has been used in Georgia (GA) to prevent the loss from leaf rust; however, with the emergence of new virulent races, these genes have lost their effectiveness. 'AGS 2000' and 'Pioneer 26R61' are the most common soft red winter wheat (SRWW) cultivars in Southeastern US, and have been used as good sources of resistance to leaf and stripe rusts, and powdery mildew. To characterize the genetic basic of resistance of AGS 2000, a mapping population of 178 recombinant inbred lines (RIL) has been developed from a cross with Pioneer 26R61. This population was genotyped using a combination of SSR, DArT, and SNP markers, and a total of 2734 markers covering the entire genome were used for the construction of genetic map. Phenotypic evaluation of parents and RIL population was conducted at the seedling stage using a virulent GA leaf rust race. QTL mapping revealed a major QTL on chromosome 2BL, explaining about 20% of total phenotypic variation in AGS 2000. Additionally, a minor QTL was also detected on chromosome 5B. QTL on 2BL was identified as a novel gene, and can be used in marker-assisted selection for leaf rust resistance.
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.
Instituto Nacional de Investigaci?n Agropecuaria (INIA)
Clara,Pritsch, Gustavo, Azzimonti, Silvia, Pereyra, Mart?n, Quincke, Victoria, Bonnecarrere, Paula, Silva, Ariel, Castro, Bettina, Lado, Silvina, Bar?ibar, Richard, Garc?a, Silvia, Germ?n, , , , , , , ,
Stem rust (SR) and Fusarium head blight (FHB) threaten the sustainability of wheat production worldwide. Sr2 is a widely used gene conferring partial, but durable, resistance to SR. Fhb1 confers a significant level of FHB resistance, but is poorly represented in the INIA-Uruguay wheat-breeding program. Sr2 and Fhb1 are linked in repulsion (~3 cM apart) on chromosome 3B. However, lines with Sr2 and Fhb1 in coupling were recently developed at the University of Minnesota, USA (kindly provided by J. Anderson). In order to incorporate Sr2/Fhb1 into Uruguayan elite wheat cultivars the donor line was crossed and backcrossed with four cultivars lacking both genes and expressing an intermediate to low level of resistance to SR and FHB: G?nesis 2375, G?nesis 6.87, INIA Madrugador, and INIA Don Alberto. Genotypes carrying Sr2/Fhb1 were selected using molecular marker UMN10; 250 BC2F1 were obtained for each recurrent parent. BC3F1 plants positive for UMN10 will be selected. The effect of Sr2/Fhb1 on response to SR and FHB in the different genetic backgrounds will be quantified by comparing disease severities of BC3F2 homozygotes with and without the UMN10 marker. Hopefully the introduction of Sr2/Fhb1 will contribute in reducing the risk of SR and FHB in wheat crops in Uruguay.
Department of BioEngineering, Birla Institute of Technology, Mesra, Ranchi, India
Manish Kumar, Kunal Mukhopadhyay
Bread wheat (Triticum aestivum L.) being the world's most popular edible cereal, plays a major role in global economy. Rust in wheat leaves, caused by Puccinia triticina, affects grain quality and severely retards its production worldwide. Micro(mi)RNAs are considered major components of gene silencing and so have a great role to play during stress. The present study focuses on identification of miRNAs, produced by host to suppress pathogen as well as delivered by pathogens to encounter host defence mechanism. Therefore, these miRNAs may be called as leaf rust responsive microRNAs. Small RNA and degradome libraries were prepared from a pair of near isogenic lines of wheat (HD2329, HD2329+Lr24), one set was mock inoculated while the other set was inoculated with urediniospores of leaf rust pathogen. Using these libraries as input a vast number of miRNAs rather a population of miRNAs were identified derived from wheat that were targeting genes mostly involved in functions like defense response, signal transduction, development, metabolism, and transcriptional regulation.
When reads specifically produced under pathogen inoculation were taken as input with Puccinia triticina genome sequences as reference, only three putative miRNA precursor loci were detected and the molecules produced were called miRNA-like molecules as their precursors lacked one or two criteria essential for a true miRNA precursor. The identified miRNAs were targeting genes like F-box protein, MAP kinase, calmodulin and susceptible antioxidant protein. We further identified the presence of argonaute and dicer like domains in Puccinia proteome available at FungiEnsembl which strengthens presence of RNAi-like activities in Puccinia.
In addition, differential expression of wheat as well as Puccinia small RNAs using stem loop RT-PCR under varying time points of disease progression (0-168 hpi) revealed their direct connection with stress responses.
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.
University of Mohammed V/ICARDA
HAFSSA,KABBAJ, AYED, AL ABDALLAT, GREGOR, GORJANC, JESSE, POLAND, MIKAEL, MILOUDI NACHIT, AHMED, AMRI, BOUCHRA, BELKADI, KARIM, FILALI MALTOUF, FILIPPO, BASSI MARIA, , , , , , , , , , , ,
Durum wheat (Triticum durum Desf.) is a major stable crop and it represents a base of the Mediterranean diet. This region is subject to a Mediterranean climate, which is extremely unpredictable with severe changes in moisture and temperature occurring each crop season. This unpredictability is summarized by breeders as GxE and the identification of traits controlling this interaction is quintessential to ensure stability in production season after season. To study the genetics of yield stability, four RILs populations derived from elite x elite crosses were assessed for yield and 1,000-kernel weights across five diverging environments in Morocco and Lebanon. These 550 RILs were characterized with 4,909 polymorphic SNPs via genotyping by sequencing. A consensus map was derived by merging the individual genetic maps of each population. Finally, imputation was used to fill all the missing haplotypes and reach a reduction of missing data to below 8%. Several significant QTLs were identified to be linked to TKW, grain yield and a stability index, namely AMMI wide adaptation index (AWAI). A second approach to identify loci controlling stability was the use of a global panel of 288 elites, accessions and landraces tested in 15 diverging environment. Multi-locations data were compiled via GxE models to derive the AWAI stability index. In addition, this panel was characterized with 8,173 polymorphic SNPs via Axiom 35K array. Significant associations were identified for all traits, including QTLs unique to AWAI. The sum of the identified QTLs can now be pyramid via marker assisted selection and molecular designed crosses in order to obtain very stable cultivars.
The University of Agriculture, Peshawar, Pakistan
Muhammad,Khan, Safi, Kathi, Zahoor, Swati, Manzoor, Hussain, Annemarie, Justesen, Muhamamd, Imtiaz, , , , , , , , , , , , , , , , , ,
Considering the importance of wheat rust diseases in Pakistan and the recent identification of yellow rust pathogen (Puccinia striiformis f. sp. tritici) centre of diversity in Pakistan, the present study was designed to assess the status of three wheat rusts across the country during 2015-16 and 2016-17 and analyze the population structure of P. striiformis f. sp. tritici . A total of 451 fields (from 68 districts) were surveyed during 2016 and 480 fields (from 69 districts) during 2017. A high yellow rust pressure was present during 2016 throughout Pakistan, while it was predominant only in the Northern half during 2017. Leaf rust was present in the central part of the country, while stem rust was only found in the south. In Sindh province (located in the south), yellow rust was reported unexpectedly with high severity (>60%) on varieties like Kiran and Galaxy during both the years. A set of 513 samples of P. striiformis were genotyped with microsatellite markers to assess the population diversity and spatial structure. and infer on the cause of epidemics in the Sindh province. Population genetics analyses confirmed a recombinant population structure across all locations except the Sindh province, where relatively lower diversity and lack of recombination signature was revealed. At least five genetic groups were identified in the overall population, which were found across all locations, except Sindh province where one of the genetic groups was predominant. The P. striiformis population from Sindh province with low diversity that caused unexpected epidemics in a relatively warmer region needs to be further investigated for specific adaptation traits. Our results confirmed the high diversity across Pakistan, which lies in the Himalayan centre of diversity of the pathogen. This high diversity was present in locations without the presence of alternate host (Berberis spp.) and could potentially be associated with regular migrants from the Berberis zone into the whole country.
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.