ICAR NRC Plant Biotechnology
The present challenge in wheat breeding is to decipher the molecular mechanisms of heat stress response and thermotolerance in detail for future applications. Several reports indicate the ability of plants to maintain a memory of stress exposure throughout their ontogenesis and even transmit it faithfully to the following generation. Here, three diverse genotypes of wheat viz., HD2967, WR544 and C306 were used for thermotolerance assays. The genotype HD2967 was able to withstand heat stress regimes (37?C and 42?C, 2 hours). Harvested seeds were sown and further raised for two consecutive years and phonotypical data evaluated in natural field condition by exposing to heat stress during generative stages in a heat trap chamber. Maximum tiller numbers and flag leaf length were noticed in second generation plant of 37?C heat exposure whereas flag leaf width in second generation 42?C heat exposure relative to the untreated plant. Auricle length showed no difference but plant height was notably increased in the second year in all the heat exposed plants. In grain yield index, ear head length was greater in the second year and fluctuations in grain number was noticed among the heat treated plant with more yields in 42?C and 42?C HTHT in the second year. IRGA and SPAD recording showed high photosynthesis and chlorophyll content in 37?C HTHT. High modulation of transcripts of several genes involved in DNA methylation and heat stress were also observed. The domino effect of heat stress in earlier generation, in this transgenerational analysis, points towards a probable epigenetic effect. Further studies are in progress to confirm and clarify the mechanisms for future manipulation in breeding for thermotolerance.
Sathguru Management Consultants
Kanan Vijayaraghavan, Venugopal Chintada, Rituparna Majumder, Richa Kapur, K. Aishwariya Varadan
South Asia has the highest "wheat dependent" low income community in the world. Stem rust and blast are recognized as the most damaging disease of wheat in the region producing 19% of the world's wheat. In order to combat the potential threat the national research centers were geared up to track the real time movement of wheat diseases, generate disease incidence data and create an enabling environment to boost wheat research in the region through streamlined efforts and enhanced SAARC tool box deployed six years ago.
Recent data (2016-17) from the tool box has shown a significant increase in the data records captured in this region compared to previous years. This has been possible because of heightened awareness amongst the scientists and with the continuous capacity building through pre-season and in-season surveillance trainings organized by Sathguru in collaboration with National Wheat Research Institutes at various levels.
The model is helping partner institutes to be self-sufficient for generating, maintaining wheat disease surveillance data in national and global databases and exchanging real time information with stakeholders. The application have been widely deployed and competently being used by 95% of rust surveillance teams in the wheat fields of SAARC region.
The study will focus on how national research center's judicious decision of carrying out diligent surveillance during the season contributed to safeguarding wheat crops in their respective nations through increased vigilance on emergence of new races and targeted introduction of regionally resistant varieties. Further using this data scientist's can aim to strategize their wheat research for identification of resistant varieties and eventually resulting in increased productivity addressing food security of the region.
The Ohio State University
Nelly Arguello-Blanco, Mao Huang
Genomic selection facilitates rapid cycling through a breeding cycle by eliminating the need to phenotype prior to selecting superior parents and crossing among them. In winter wheat we can now complete a cycle of GS in about 12 months and two greenhouse seasons. Season consists of planting F1s from the previous cycle and selfing to obtain F2 seed. The second season involves planting and genotyping the F2s, predicting their value with GS, selecting and crossing the best, and harvesting the F1 seed. Our breeding program has completed five cycles of GS in one population primarily for grain yield, over the past five years. We have completed three cycles of GS for resistance to Fusarium Head Blight in a second population. Genotyping was done using genotyping-by-sequencing. This provides an opportunity to assess the changes in the population that have occurred as a result of this rapid cycling. These include 1) changes in genomic estimated breeding values for grain yield and FHB resistance, 2) effect of selection and drift on allele frequencies including fixation, 3) effect of selection on diversity and genetic relationships, and 4) changes in linkage disequilibrium. We are conducting these analyses and will present the results.
Institute of Evolution and the Department of Evolutionary and Environmental Biology, University of Haifa, Israel
Dina Raats, Lin Huang, Valeria Bocharova, Jorge Dubcovsky, Abraham Korol, Tzion Fahima
Wild emmer wheat (Triticum dicoccoides, (DIC)) is an important source of resistance to stripe rust due to presence of Puccinia striiformis in its natural habitats with high humidity and relatively low temperatures that are favorable for stripe rust development. Previously, we showed that DIC accessions from northern Israel were highly resistant to stripe rust. According to the rust responses of three DIC accessions (G25, H52, G303) and mapping of the resistance to relatively close, but different, genetic positions on chromosome 1BS, three different resistance genes were assumed to be present. However, the development of additional critical recombinants and new higher resolution genetic maps for these three genes in subsequent work led us to place YrH52 and YrG303 in the same genetic interval as Yr15, suggesting that the three putative genes are allelic or identical. The recent cloning of Yr15 allowed us to test this hypothesis using an EMS mutagenesis approach. We sequenced the Yr15 locus in five yrH52 and three yrG303 susceptible mutants and identified missense point mutations associated with the susceptible phenotype in each one. Thus, YrH52 and YrG303 may not be new genes. Further work is under way to determine if these genes are allelic or identical.
Genetic Resources Institute, Azerbaijan
N. Aminov, A. Jahangirov, H. Hamidov, Aigul Abugalieva, Vladmir Shamanin, Alexey Morgunov
Hexaploid synthetics have become widely used in bread wheat improvement in recent years, enabling the introduction of specific traits as well as enhancing genetic diversity and development of valuable germplasm. This study demonstrated the difference between two groups of primary synthetics in terms of development rate, plant height, rust reactions, and productivity components. During 2015 and 2016, three groups of synthetics were studied in Azerbaijan (3 sites): Baku (0 masl) under irrigated conditions, Gobustan (850 masl) under dry rainfed conditions and Ujar (20 masl) under irrigated conditions with high salinity. Germplasm was also evaluated for diseases and agronomic traits in Omsk (Russia) in 2016.
All primary synthetics were resistant to leaf rust, several to stem rust, and few to stripe rust. Stripe rust occurred in all years at all sites, proving its importance as major wheat pathogen. Its severity reached intermediate levels in Baku in 2016 (33.7%) and in Gobustan in 2015 (26.8%), and epidemic level in Gobustan in 2016 (72.7%). Gobustan also experienced high levels of stem rust in 2016. These two diseases substantially reduced grain productivity in Gobustan in 2016, especially 1000 kernel weight (30.2 g) and grain weight per spike (1.17 g). . Superior genotypes from all three groups were identified that combine high expression of spike productivity traits and stress tolerance index. Five superior synthetics were selected from each of the three groups, based on grain weight per spike. Only four of these demonstrated resistance to stripe rust (entries 13, 15, 31, and 32). Japanese synthetics (group 3) were susceptible to stripe rust but all demonstrated resistance to stem rust. Synthetics from groups 1 and 3 were all resistant to leaf rust when tested under severe disease pressure in Omsk in 2016.
ICAR-IIWBR, Regional Station, Flowerdale,Shimla 171002 H.P. India
Pramod Prasad, OmPrakash Gangwar, Hanif Khan, Siddanna Savadi, Subodh Kumar
Stem rust (Puccinia graminis tritici) (Pgt) epidemics have been reported from many wheat growing areas of the world. Stem rust races with virulence to Sr31 (Ug99 type races),are a threat to wheat producing African countries. Currently 11 different variants of the Ug99 lineage have been reported from different countries. Despite no report of Ug99 variants from any of the South Asian countries, the efforts are in place to counter the possible introduction of virulent wheat stem rust races. Stem rust surveillance has been a major component of the rust resistance breeding worldwide. This study reports virulence phenotypes and functional SSR marker based genotypes among stem rust collections in the Indian subcontinent during 2009 to 2015.
Wheat stem rust samples were analyzed on differential sets used for pathotype identification in India. Twelve pathotypes of Pgt were identified in a total of 574 samples analyzed. Pgt pathotypes 40A and 11 were identified in 36% and 32% of the samples, respectively. The stem rust resistance genes Sr7a, Sr26, Sr27, Sr31, Sr32, Sr33, Sr39, Sr40, Sr43, SrTmp and SrTt3 were found to confer resistance to the field population identified during this period. The analysis of SSR marker genotypes data revealed a high degree of variability in the Pgt population, with mean gene diversity and polymorphic information content (PIC) values of 0.56 and 0.50, respectively. STRUCTURE software divided the Pgt populations in to four subpopulations with some admixtures. The FST values of pairs of subpopulations ranged from 0.35 to 0.93 which indicated that the four sub-populations were significantly differentiated. The analysis of molecular variance (AMOVA) determined that 16%, 69% and 15% of the totl variation was between population, among and within individuals, respectively. The information generated here could be a useful guide for resistance breeding and gene deployment programmes for saving South Asian wheat from stem rust.
National Agronomic Research Institute of Algeria
Among the many biotic constraints to wheat production in Algeria, rusts and in particular yellow rust (Puccinia striiformis), are among the most prevalent diseases that occur mostly all over the northern part of the country. Yellow rust has become now sporadic due to the exploitation of effective resistant genes in different forms and combinations (from CIMMYT and ICARDA). Earlier, durable resistance was probably due to many genes, such Yr18, Yr9, Yr27 and Yr1.
Yellow rust appeared as epidemic in 2004, over 600 000 ha of bread wheat ; severity exceeded 70%. Yields from affected fields of Hidhab a susceptible variety did not exceed 5.2 q/ha, while resistant cultivars yielded up to 48 q/ha. Monitoring of the pathogen virulence factors and their changes provides basic information for the development of an early warning system. This experiment was carried out in 5 Eastern Algeria locations. 30 lines of a standard set of yellow rust and 14 near-isogenic lines from ICARDA were sown in 2-m rows in 2014 and 2015. According to the results, virulence on Heines Kolben (Yr2), Kalyansona (Yr2), Lee (Yr7), Avocet R (YrA), Federation*4/Kavkaz (Yr9), Yr6/6*Avocet ?S?, Yr7/6*Avocet ?S?, Yr9/6*Avocet "S", Yr17/6*Avocet "S", TP1295 (Yr25) and YrSU was common during those two seasons. The frequency of virulence on plants with Yr2, Yr6, Yr7, Yr9 or YrA and Yr27 was up to 80%. No virulence was observed on plants with Yr1, Yr3, Yr4, Yr5, Yr8, Yr10, Yr15 and Yr18 genes. This material was extensively used in our breeding programs and several new cultivars are in the on farm trials where a participatory selection approach is used. All resistant and performing new varieties are being spread for replacement of most old susceptible ones.
The University of Sydney
Davinder Singh, Peter Dracatos
Following the introduction of wheat stripe rust into Australia in 1979, an uncharacterized resistance (YrA) was identified in both Australian and International spring wheats. Genetic analyses of YrA indicated it was a pair of complementary genes, which were mapped to chromosomes 3DL and 5BL and designated Yr73 and Yr74, respectively. While selection Avocet 'R' carries both genes, selection Avocet 'S' carries Yr73 only. P. triticina pathotype (pt.) 104-1,2,3,(6),(7),11 +Lr37 ("104-VPM"), first detected in Australia in 2002, most likely arose via mutation from pt. 104-1,2,3,(6),(7),11 ("104"), with added virulence for Lr37. Interestingly, while both pathotypes are avirulent on Lr13, 104-VPM shows a much lower Infection Type (IT, ";1") than pt. 104 ("X++3") on several genotypes carrying Lr13 (e.g.Avocet 'R', Avocet 'S'). Other Lr13 genotypes (e.g. cv. Hereward) respond similarly to both pts ("X++3"). Genetic analyses of 4 doubled haploid (DH) populations based on intercrosses between Avocet 'R' and genotypes lacking Lr13 segregated in a 1:7 ratio to pt. 104-VPM (";1" : all other ITs). Two populations fixed for Lr13 (viz. Hereward/ Avocet 'R' and Estica/Avocet 'R') segregated 1:3 to pt. 104-VPM (";1" : all other ITs). This segregation pattern fitted a model where two complementary genes interact with Lr13 to generate the low (IT ";1") IT. Mapping of a Teal/Avocet 'R' DH population using 92 lines and 9,035 DArT-Seq markers identified three QTLs: chromosome 2BS (Lr13); chromosome 3DL (co-located with Yr73); chromosome 1DS. These results suggest that Yr73 acts in a complementary manner with a gene on chromosome 1DS to confer leaf rust resistance (IT "X"), and that these complementary genes are additive with Lr13. It appears that Yr73 is a modifier of two independent genes in wheat, one conferring resistance to stripe rust (Yr74 on chromosome 5BL), and one conferring resistance to leaf rust (LrAv on chromosome 1DS).
Department of Botany, Faculty of Biology, Government College Murree, Pakistan
Barkat Ali, Muhammad Fayyaz, Atiq ur Reman Rattu, Abdul Samad Mumtaz, Muhammad Imtiaz
The new arrival of wheat rust pathotypes through migration during wheat cropping season requires regular monitoring to secure wheat production. In the present study, we collected leaf rust (Puccinia triticina Eriks.) infected wheat leaves from three major wheat growing provinces of Pakistan in the year 2014 to assess the haplotype diversity of P. triticina (Pt) isolates. The rDNA ITS sequence data of collected isolates was used in NCBI BLAST analysis. The blast hits showed best matches with Pt accessions EU014050 (Iran), JN120331 (Iran), JX533577 (Iran), AY956549 (Iran), DQ417412 (Czech Republic), DQ417418 (Israel), DQ417413 (Slovakia) and AF511083 (Louisiana). However, in cluster analysis, the Pakistani isolates showed strong bootstrap support with only Iranian and Indian (races 77-5 & 104-4) accessions that indicated eastward migratory mode of Pt pathotypes in Pakistan through westerly wind patterns. The predominant genotype DQ417412 (similar in alignment with AY956549 from Iran) overcome the resistance of top Pakistan mega varieties Seher06, Inqilab91, Kiran95, SKD1, TJ83 and NIFA-Batoor. Hence, the ITS based information remains a rapid molecular tool for pathogen surveillance across countries and continents.
Institute of Plant Biology and Biotechnology
Makpal Atishova, Aygul Madenova, Kanat Galymbek, Jenis Keyshilov, Hafiz Muminjanov, Alexey Morgounov
Wheat rust diseases are a major cause of yield losses of this crop. Yellow (Puccinia striiformis f. sp. tritici) rust is of the most widespread and dangerous disease of wheat and is the major factor that adversely affects wheat yield and quality. The use of genetic host resistance is the most effective, economical and environmentally safe method of controlling stripe rust that allows elimination of fungicides and minimize crop losses from this disease. Due to the threat of the development of epiphytoties of rust disease it is necessary to identify new donors of resistance to yellow rust and to develop resistant wheat breeding material. In the present study, attention was drawn to the effective yellow rust resistance genes Yr5, Yr10 and Yr15, which were identified in the process of molecular screening of wheat germplasm. Genetic analysis using S23M41 molecular marker linked to Yr5 revealed the presence of this gene in 17 out of 136 promising lines. Thirteen genotypes screened with Xbarc8 generated the DNA fragment associated with Yr15. Three advanced lines with Yr10 were identified using the SCAR marker. Three lines carrying two Yr genes (Yr5 and Yr15) were detected. Combination of Yr5 and Yr10 were found in 15 wheat lines. We identified a number of wheat genotypes highly resistant to stripe rust, which could be further evaluated to release new resistant varieties or to be used in the breeding program.