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.
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.
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.
Instituto Nacional de Investigaci?n Agropecuaria (INIA) La Estanzuela
Paula Silva, Clara Pritsch, Miguel Raffo, Silvia Pereyra, Silvia German
Wheat stem rust (SR), caused by Puccinia graminis f. sp. tritici, (Pgt) is considered one of the most destructive diseases of the wheat crop. As Sr24 and Sr31 are the most widely used resistance genes in the Southern Cone of America, wheat crops in this region is under threat of SR outbreaks posed by the potential migration of virulent Pgt Ug99-lineage races (Ug99+). Efforts have to be made to develop adapted lines resistant to Ug99+. Genes Sr26, Sr32 and Sr39 are effective to both Ug99+ and local races of the pathogen. This work is aimed to pyramid two and three of the resistance genes in two locally adapted wheat cultivars (G?nesis 2375 and G?nesis 6.87). Donor lines of Sr26, Sr32 and Sr39 (developed by I. Dundas, University of Adelaide, Australia) and molecular markers Sr26#43, csSr32#1 and Sr39#22r (developed by R. Mago et al., University of Adelaide) were used. Lines with two-gene combinations were developed in two steps. First, tree-way crosses were made by crossing heterozygous F1 plants (derived from crossings donor lines) to either one of the two adapted wheat cultivars. Subsequently, tree-way F1 plants were genotyped and only those with two-gene combinations were backcrossed (BC) twice to the adapted cultivars. Among three-way F1 plants, two-genes combinations were confirmed for Sr26+Sr32 (8 out of 31), Sr26+Sr39 (2 of 115) and Sr32+Sr39 (26 out of 103). In the BC1F1 generation, Sr26+Sr32, Sr26+Sr39 and Sr32+Sr39 combinations corresponded with 9, 9 and 45 out of 99, 27 and 241 plants, respectively. In 2017, 1345 BC2F1 plants are being grown to obtain BC2F2. We plan to intercross plants with two-gene combinations to obtain lines with the three genes which will be used as sources of resistance to develop cultivars with presumably longer lasting resistance to wheat SR.
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.
ICAR- Indian Institute of Wheat & Barley Research, Karnal-132001, India
Vinod Tiwari, DP Singh, RP Gangwar, GP Singh
The changing climatic conditions are affecting wheat production in major agro-ecological zones in India, namely, north western plains(NWPZ), north eastern plains(NEPZ), central (CZ) and peninsular zone(PZ) where the reproductive phase has to endure higher temperatures. Also, the prevalence and virulence of rust pathotypes and other diseases are affected. To address such challenges, development of wheat for climate resilience was initiated following shuttle breeding approach for incorporating heat stress tolerance as well as resistance to wheat rusts. During 2010-16, a total of 583 elite lines were evaluated against prevalent pathotypes of stripe rust 78S84, 110S119, 110S84 and 46S119; leaf rust 12-2(1R5), 12-5(29R45), 77-2(109R31-1), 77-5(121R63-1), 77-9(121R60-1) and 104-2 (21R55) and stem rust 11(79G31), 40A(62G29), 42(19G35), 122(7G11) and 117-6(37G19) of which 108 promising entries were identified. These lines were evaluated for disease response in multilocational Initial Plant Pathological Screening Nursery (IPPSN) against prevalent races of all three rusts. Based on average coefficient of infection (15.0 ACI), 42 (39%), 104 (96%) and 90(83%) entries were found resistant to different races of stripe, leaf and stem rusts, respectively. Based on performance in multiplication yield trials, 29 entries were contributed in national coordinated evaluation system on Wheat & Barley which resulted in release of four wheat cultivars DBW71(Yr9+27+,Lr26+,Sr2+5+31+), DBW107(Yr9+,Lr26+3+,Sr31+), DBW110(Yr2+, Lr13+10+,Sr13+11+) and DBW93(Yr9+, Lr26+23+, Sr31+) for commercial cultivation in NWPZ, NEPZ, CZ and PZ, respectively. These cultivars are becoming popular among farmers due to their yield advantage, resistance to diseases, tolerance to high temperature and better quality traits. Also, DBW 129 was screened in multiple disease screening nursery (MDSN) and observed resistant to all rusts, leaf blight, powdery mildew, flag smut and shoot fly. The adoption of the newly developed cultivars for deployment of differential genes for resistance would lead to reduction in disease pressure and bring higher profitability to farmers in different agro-ecological zones in India.
The Federal Research Center Institute of Cytology and Genetics, The Siberian Branch of the Russian Academy of Sciences
Vyacheslav Piskarev, Irina Leonova, Ekaterina Bukatich, Elena Salina
Stem and leaf rusts affect the winter and spring wheat in the Novosibirsk region. During 2008-2017 leaf rust incidence was generally moderate, from 20 to 40%. A leaf rust outbreak occurred in 2015 when incidence increased up to 80%. Leaf rust severity on the 'Thatcher' NILs ranged from immune or resistant to highly susceptible host response with maximum severity of 90S. Lines carrying genes Lr17, Lr18, Lr24, Lr29, Lr35, Lr37, Lr44, and LrW remained almost free of infection for the whole time of inspection. Genes Lr12, Lr13, Lr28, Lr34, and Lr38 exhibited moderate resistance but they did not provide sufficient level of resistance in favorable conditions. Since race-specific genes Lr24 and Lr29 are still effective in the neighboring Novosibirsk and Omsk regions, they might be recommended for breeding purposes in Western Siberia.
In 2016 stem rust was more prevalent and widespread in the region than ever before. Disease incidence ranged between 4.5 - 60% with high severity up to 80S in six fields from seven observed locations. The 4th ISRTN and varieties carrying Sr31 of West Siberian germplasm were assessed in field trials to monitor the virulence of the local population. There was no virulence to Sr9b, Sr9e, Sr20, Sr28, Sr29, Sr33, Sr39, Sr40, SrWld, Sr2 complex. Possible virulence to Sr6, Sr11, Sr12, Sr13, Sr17, Sr24, Sr25, Sr30, Sr31, Sr35, Sr38, Sr44, Sr57 was observed with low frequency. Entries genotyped for gene Sr31 were scored as MS and S. However, follow up race analysis work is needed to determine the actual stem rust races present and confirm the suspected possible observed virulence on Sr31.
Institut National de la Recherche Agronomique INRA Morocco
Kumarse Nazari, David Hodson, Tine Thach, Julian Rodriguez Algaba, Mogens Støvring Hovmøller
Wheat rusts, notably yellow rust, are amongst the most damaging diseases on wheat in Morocco. The objective of this survey was to assess the incidence and severity of wheat rust diseases across Morocco. The survey was carried out during April-May 2017 where growth stage of wheat ranged from anthesis to physiological maturity. The severity and response rating for the adult plant field reaction to rusts were based on the modified Cobb scale. A total of 117 bread wheat fields were inspected. The survey revealed that the most prevalent disease was yellow rust (96 out of 117 fields). Leaf rust, SLD (Septoria Like Diseases) and to some extent root rot complex were less prevalent. Leaf rust was only observed in 8 out of 117 inspected fields and exhibited low severity. Stem rust was observed in only one field. Following the drought of 2016, the 2017 growing season was an epidemic year for yellow rust in Morocco. It was detected across all regions and 50% of inspected fields were highly infected. Those that were lightly or not infected were sprayed with fungicides up to two times. Almost all commercial bread wheat cultivars in Morocco are highly susceptible to yellow rust. Appearance of new virulent races is leading to the breakdown of resistance in major cultivars e.g., Arrihan, which had very few pustules of yellow rust in 2013 was highly susceptible in the last three years. Samples of yellow rust from 2016 revealed a new virulent race in all samples, temporarily designated Pst (new) [virulence pattern: [Yr-,2,3,-,-,6,7,8,9,-,-,17,-,25,-,32,Sp,AvS,-]. Thirty-four samples submitted to GRRC in 2017 were all of the same genotype, identical to the new race already detected in 2016. The results demonstrate that surveillance and genotyping/race phenotyping of samples may be important for early-warning and anticipatory breeding strategies.
Emel Ozer, Mehmet Karaman, Mozaffar Roustaii, Jalal Kamali
Erratic weather patterns associated with climate change pose unique challenges for wheat breeders playing a key part in the fight to ensure global food security. Within the rainfed winter wheat areas of Turkey and Iran this erratic weather patterns may prevent attaining maximum potential increases in winter wheat genetic gains. This is primarily related with the fact that the ranking of tested varieties may greatly change from one year to the other. Erratic weather patterns may interfere with breeders decision on the ideotype(s) they should aim for during selection. To support breeding decisions, this study aimed at optimizing major traits through modelling different combinations of environments and defining probabilities of the range of variation of traits (phenology and pant height) that maximized grain yields. Optimal phenology was found to be highly related with the temperatures at which the winter wheat varieties were exposed at around heading time (20 days before and after heading). Specifically later winter wheat varieties were exposed to higher temperature both before and after heading and this exposure had a negative effect on grain filling duration and final grain yield. Finally, the use of at least five different wheat varieties in one production field (with different phenology and plant height) was compared to a field with monoculture to test for improved resilience. It was concluded that by selecting one best wheat variety in a wide range of environments it was possible to maximize grain yield and that using a set of diverse varieties was not beneficial.
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.