National Institute of Agriculture Research, Tunisia
Meeting food security challenges is a high priority in many developing countries. North African countries are among those with the highest per capita wheat consumption in the world and chronic grain deficits. Climate change scenarios predict decrease of rainfall and increase of temperature with negative impact on crop production and hence food security. Along with adoption of modern technologies, breeding higher yielding and more climate change resilient wheat varieties is widely seen as a tool that can sustain past yield gains and food production increases. Durum wheat production in Tunisia greatly benefited from the green revolution ingredients. Continued breeding lead to replacement of the early semi dwarf varieties with higher yielding, better disease resistant and more drought tolerant ones that have positively impacted yield at farmer and national level. Monitoring gains from increased yield potential and resistance to the most damaging foliar diseases, mainly septoria leaf blotch, leaf rust and stripe rust, showed that grain yield of recently released varieties is up to four times that of the tall late maturing landraces grown before the 1970's and up to 2.5 times that of varieties of the early years of the green revolution. Chlorophyll content, green leaf duration, deeper root development from diverse donors including wild wheat relatives and grain yield are being integrated in the breeding program for the selection of more drought and heat stress tolerant durum cultivars
Yellow rust caused by Puccinia striiformis f.sp. tritici, is the most devastating fungal disease of wheat, especially in CWANA region. Growing cultivars with durable resistance is the most economical control measure. A field study was conducted to evaluate 500 bread wheat landraces along with the susceptible control ?Morocco? using artificial inoculation under field conditions at Tel Hadia, Syria during 2010-11 and 2011-12 growing seasons. The most prevailing yellow rust virulent race 70E214 was used for artificial inoculation. The disease scoring started when the disease severity was more than 50 % on the leaves of the susceptible check ?Morocco? and continued for four scorings at the intervals of 7 days. Slow rusting resistance was assessed based on the development of disease over time using the Area under Disease Progress Curve (AUDPC), Coefficient of Infection (CI), Final rust Severity (FRS), Infection Rate ?(r)? and Relative Resistance Index (RRI). None of the landraces showed immune reaction and 10% showed lowest values for all parameters, suggesting that resistance in these landraces was controlled by major genes. Approximately 65% of landraces were marked as having different levels of slow rusting and 25% were highly susceptible. Cluster analysis based on partial resistance parameters revealed two major clusters: Susceptible and low level of slow rusting were grouped in the first cluster; Resistant, high level and moderate level of partial resistance were grouped in the second cluster. By comparing the results obtained from RRI and others parameters, we found that landraces with very low values for all parameters exhibited high RRI value of 9, while those that showed high, moderate and low levels of slow rusting, had RRI ranges of 8-9, 7-8 and 5-7, respectively. The landraces with maximum values from each parameter showed very low RRI values of less than 5.
Crop Development Centre/Department of Plant Science, University of Saskatchewan, Saskatoon, Canada
Sajid Ali, Dinah Qutob, Steve Ambrose, Ron Maclachlan, Kun Lou, Curtis Pozniak, Yong-Bi Fu, Andrew Sharpe, Randy Kutcher
Puccinia striiformis f. sp. tritici (Pst), the cause of wheat stripe rust, is one of the most important pathogens of wheat. Attempts have been made in the past to characterize the worldwide genetic structure of Pst populations, excluding Canada. Characterization of 59 isolates identified 33 races with three most common races representing half of the population and subtle differences in races of eastern and western prairies. For molecular characterization, 48 isolates were sequenced to obtain SNPs and genotyped with Pst-specific SSR markers. Isolates that were suspected of recombination based on SNP data were examined for their telia production ability as a proxy for sexual recombination. The study revealed that the majority of the population was clonal, however, not exclusively clonal, with the existence of four genetic lineages. Two lineages previously reported were identified: PstS0, representing an old northwestern-European and PstS1, an invasive warmer-temperature adapted lineage. Additionally, two new lineages, PstPr and PstS1-related, were detected that have not been reported previously. The PstPr and PstS1-related lineages produced more telia than the other lineages and had double the number of unique recombination events compared to PstS0 and PstS1. PstPr was concluded to be a sexual recombinant and an exotic incursion, which was closely associated with PstS5, PstS7 (Warrior), and PstS8 (Kranich) lineages, all of which arose by sexual recombination in the center of diversity - the Himalayan region. The total phenotypic variation in the population could not be explained solely by molecular genotypes, and a hypothesis on existence of epigenetic machinery in the Pst genome was tested. Homologs of the DNMTases class (DNMT1) were identified, providing compelling evidence of a role for DNA methylation. As a first report of DNA methylation, an average of ~5%, 5-methyl cytosine (5-hmC) in the Puccinia epigenome indicated the possibility of epigenetic regulation, which merits further investigation.
Prashant,Vikram, Deepmala, Sehgal, Juan, Burgueno, Carolina, Sansaloni, Cynthia, Ortiz, Ernesto, Solis, Lulu, Ledesma, Pillar, Suaste, G, Fuentes, J, Ireta, A, Sharma, P, Srivastava, Sridhar, Bhavani, Thomas, Payne, V, Govindan
Wheat breeding programs have successfully harnessed the potential of elite germplasm pool and have contributed significantly to global food security. However, to obtain additional genetic gain, useful diversity for key traits from landraces, synthetics and wild relatives should be incorporated in breeding germplasm pool. Maladaptation and linkage drags are the bottlenecks in utilizing these exotic genepools for pre-breeding. A systematic, focused, large scale effort has been pursued at CIMMYT through a three-way cross (exotic x elite1 x elite2) population development strategy. Population was advanced through selected-bulk scheme in way to select relevant genetic diversity while maintaining large population sizes. A total of 984 advanced pre-breeding lines (PBLs) were evaluated in multiple environments for grain yield related traits, micronutrient content and diseases resistance (yellow rust, stem rust, powdery mildew, and karnal bunt). Potential useful lines for these traits have been identified. High-density genomic characterization of PBLs, parental elites and exotics was conducted through a "haplotype map" based approach, which revealed 16% (58/361) exotic specific haplotype block (HB) introgression in PBLs. Out of 58 exotic specific HBs, 12 (12/361 = 3%) were found associated with traits evaluated in the study. Three HBs, H1.28 (1A), H18.1 (6D) and H5.23 (2B) were significantly important as they showed consistent effects across environments for grain yield (1A and 6D) and yellow rust (2B). This significant contribution of exotics into PBLs opens avenues to mine and utilize their useful alleles in wheat improvement. This research describes systematic large-scale pre-breeding efforts, as proof of concept of exotic germplasm deployment to the breeding pipelines simultaneously enriching genetic knowledge through high-density genomics analysis. Genetic knowledge coupled with breeding efforts should provide substantial gain required for next generation wheat varietal improvement.
Department of Agriculture, Sunsari, Nepal
Wheat (Triticum aestivum L.) is one of the major cereal crops vital for global food supply. Most of the wheat crop in developing world including that of Nepal is either grown with limited irrigation or under rainfed conditions and thus face moisture stress at one or more growth stages limiting grain yield. An experiment was carried out at the Institute of Agriculture and Animal Science, Rampur to evaluate the genetic variability of selected drought adaptive traits in Nepalese wheat germplasm. The wheat genotypes evaluated comprised of Nepalese landraces and commercial cultivars, CIMMYT (International Center for Maize and Wheat Improvement) derived advanced introduction lines and three checks with differential drought adaptability. The wheat genotypes were grown in pots (single plant) arranged in a replicated split plot design in greenhouse under two contrasting moisture regimes, optimum and moisture stressed. The genotypes were evaluated for water use, water use efficiency, relative leaf water content and biomass production. The ANOVA (Analysis of Variance) revealed significant variation between environments and among the wheat genotypes for most of the traits studied. A wide range of variability was observed for water use, water use efficiency, biomass yield and relative leaf water content in moisture stressed and non-stressed environments. Nepalese cultivar Gautam showed a number of favorable drought adaptive traits, whereas, Bhrikuti was average in this respect. Based on the scores of drought adaptive traits recently released Cultivar (cv). Vijay was characterized as drought sensitive. A number of landraces and advanced breeding lines showed high level of water use efficiency and other positive traits for drought adaptation.
Lake Chad Research Institute, Maiduguri, Borno State-Nigeria
Dattijo Aminu, Zakari Goji Silas Turaki, Fatima Henkrar, Udupa Sripada
The research was conducted at ICARDA, Rabat. Twenty-four accessions were obtained from LCRI for marker analysis. Wizard Genomic DNA Purification Kit was used for DNA extraction. DNA was extracted by CTAB method and quantified using 1.0 % (w/v) agarose gels. Total of 12 loci, 5 functional and 7 linked random DNA markers to the traits of interest were used. PowerMarker and DARwin software were used to calculate the No. of alleles and values of genetic diversity, PIC, genetic distance, and NJ dendrogram. The total No. of detected alleles was 39; and mean No. of alleles was 3.25. No. of alleles range from 1 (Dreb-B1) to 9 (Xgwm577). Genetic diversity index ranged from 0.0000 in Dreb-B1 to 0.8471 in Xgwm577. The PIC value was also varied from 0.0000 (Dreb-B1) to 0.8296 (Xgwm577). The frequency of biotic resistance linked random DNA marker allele at Xgwm144 and Xwmc44, associated with yellow and leaf rust gene was 25% each. Marker alleles Xgwm577 and Xgwm533 linked to Stb2 and Stb8 at 150 and 120bp have frequencies of 21 and 4%. The frequency of abiotic resistance showed 50% of accessions had 1R segment (1BL.1RS translocation) and 58% of accessions showed presence of 120bp allele of Xwmc89, associated with QTL for drought tolerant. Functional marker alleles of Dreb-B1 associated with drought tolerant genes showed alleles frequency in all accessions. Linked marker allele Xgwm111 linked to heat tolerant gene showed 17% allele frequency at 220bp. Rht1 and Rht2, the allele frequencies were 92 and 4%. 92% of the cultivars had photoperiod insensitive allele at Ppd-D1 locus. VrnA1a and VrnA1c primer pair amplified at 965, 876, and 484bp, allele frequency of 13 and 87%. Cluster analysis had grouped the accessions into 5 at a genetic distance level 0.15.
University of Queensland
Genomic selection (GS) in wheat can accelerate yield gain principally through a reduction in breeding cycle duration. A method for rapid generation advance called ?speed breeding? (SB) enables up to six generations of spring wheat per year, and could be used to accelerate breeding population development and be combined with GS in various breeding schemes to enable even further gains. SB and GS could be combined through a variety of different scenarios using single seed descent and also by applying GS to segregating populations in the glasshouse. Selected lines could then go into multi-location field trials for final selections and to obtain information for updating the prediction model. The increase in speed in these scenarios compared with field-based breeding schemes could greatly improve genetic gain for valuable target traits, such as yield. To test these hypotheses, a 260 multi-parent spring wheat population, genotyped with 8,000 DArT polymorphic markers, underwent yield trials over three years. Yield prediction accuracy was accessed using five-fold cross validation and predicting across years. Using these results, the rate of genetic gain achieved through either phenotypic selection in the field or a combination of SB and GS in the glasshouse were calculated. Results indicate that incorporating GS into SB growing systems would result in a higher rate of genetic gain compared to phenotypic or more traditional GS breeding schemes, due to the greater number of generations produced per year. This approach may be able to be coupled with multi-trait GS prediction models to increase accuracy, advance genetic gain and wheat variety development.
John Innes Centre
Burkhard,Steuernagel, Caixia, Lan, Miroslava, Karafi?tov?, Ksenia, Krasileva, Jaroslav, Dole?el, Evans, Lagudah, Ravi, Singh, Brande, Wulff, , , , , , , , , , , , , ,
Adult Plant Resistance (APR) genes are broad-spectrum, partial-resistance genes that have the potential to contribute to sustainable control of wheat rust diseases. However, their isolation and characterization are complicated by the lack of precise molecular markers required for their identification, and therefore their use in plant breeding programs has been limited. Recent developments including the falling cost of sequencing and the increasing use of sequence capture methods to reduce genome complexity have enabled previously intractable methods such as mutational genomics to clone genes in wheat. Despite their increasing ease of use, many of these approaches require prior knowledge of the gene space and, in some cases, the gene family of the target gene to be cloned. As the APRs cloned so far do not belong to any common gene family, it is not possible to use general features of these identified APRs to conduct biased searches for novel APRs. This project aims to use an unbiased gene isolation technique called MutChromSeq, which combines chromosome flow-sorting and mutational genomics, and is independent of fine mapping, to rapidly clone the recently discovered APR gene Lr68 (Leaf Rust 68). Cloning APRs allows breeders to trace genes cheaply and quickly using gene-specific markers, enabling them to build effective and durable resistance gene pyramids. It also allows us to elucidate any common mechanism of action they have, helping researchers and breeders understand better the basis of their durable resistance. At the same time, the generation time of wheat has become one of the major limiting factors for the response time of breeders to rust epidemics. Thus, this project also aims to combine marker-assisted selection with accelerated generation advancement ('speed breeding') for rapid germplasm structuring and field performance evaluation.
University of Agriculture, faisalabad
Drought tolerance is a polygenic trait, with a complicated phenotype, often confused by plant phenology. Breeding for water stress is more complex since there are many types of abiotic stresses, such as drought, heat and salt. High yielding wheat genotypes viz., Miraj-06, 9452, 9469, 9272, 9277, CMS-127 and three testers Chakwal-50,
Kohistan-97 and Aas-11 were crossed in line ? tester mating design. Seed obtained from crosses was evaluated in field conditions for various agronomic traits under drought conditions. Recorded data were subjected to analysis of variance to determine the genetic variability. The data were analyzed statistically and combining ability
studies were tested using line ? tester analysis to find the relationship between different traits of wheat. High significant differences were observed among the lines and testers for yield related traits under stress conditions.
The female line 9452 proved to be best line on the basis of mean performance of traits under water stress. In case of testers, the male parent variety Chakwal-50 retained its performance in maximum number of traits closely followed by Aas-11. The cross combination 9272 ? Aas-11 proved best for attaining highest mean for most of
traits. In case of GCA effects line 9277 and tester Aas-11 proved best. The cross combinations 9277 ? Chakwal-50, 9452 ? Kohistan-97 exhibited highest SCA effects. The superior genotypes and crosses can be combined to develop new promising and improved varieties under water stress conditions.
John Innes Centre
Christopher,Judge, Francesca, Minter, Nik, Cunniffe, Richard, Morris, Diane, Saunders, , , , , , , , , , , , , , , , , , , ,
Wheat yellow rust is a disease caused by the fungus Puccinia striiformis f. sp tritici (PST) that is a significant threat to wheat production worldwide. Recently, a novel approach called "Field Pathogenomics" was developed that allows acquisition of genotypic data from field samples of PST-infected wheat. This has enabled us to study the re-emergence of this pathogen in the UK and understand the different races that form the current PST population. However, the dynamics of pathogen transmission and dispersal still remain unknown and understanding this is essential for designing effective surveillance. The objective of this project is to develop a spatially-explicit model for the spread of PST that can contribute to better management of the disease and be used as a warning system for wheat yellow rust infection in the UK. The first aim is to study how PST spreads at the field level and determine whether there are differences between PST races in terms of disease dynamics. To this end, a set of markers have been designed that can be used to genotype field-collected isolates and determine which race they belong to. Field trials were also undertaken across the UK using wheat varieties that are known to be susceptible to the disease, with PST-infected wheat samples collected during the 2015-2016 and 2016-2017 seasons. These samples will be genotyped to study the prevalence of different PST races and determine whether PST genotypes identified early in the season are predictive of dominant genotypes found later in the season. Understanding PST dynamics within a field is key to build an epidemiological model that can predict how this disease behaves. This would improve disease management, targeting of chemical sprays and optimize pathogen surveillance.