Umesh,Rosyara, Suchismita, Mondal, Ravi, Singh, Susanne, Dreisigacker, , , , , , , , , , , , , , , , , , , , , ,
Grain yield is the most important economic trait in wheat breeding. The detailed understanding of the genetic architecture of grain yield is crucial and the determining factor to optimize genomics-assisted selection strategies in wheat. First, we performed a marker and haplotype-based genome-wide association study (GWAS) for grain yield (GY) and yield stability coefficient (Pi) on 4,302 advanced breeding lines from five CIMMYT international bread wheat trails grown in multiple (optimally irrigated and stress) environments. All lines were genotyped using genotyping-by-sequencing. A haplotype map was built based on linkage disequilibrium between markers. Twenty-nine markers and 16 haplotypes were associated with GY and Pi across two and three germplasm trials with allelic effects ranging from 2 to 11% across environments. Secondly, we performed genomic prediction, testing eight different prediction models incorporating single markers (base model), haplotypes, epistatic interactions, and significant markers/haplotypes identified in GWAS. Initial results show that by including haplotypes and epistatic interactions among haplotypes (main effect and genome-wide), prediction accuracies range between 0.33-0.49 for GY, a 3 to 22.5% improvement over the base model. Despite the identification of significant marker/haplotype trait associations across traits and environments in GWAS, accounting for these markers in genomic prediction does not improve the prediction models. Our results suggest that the haplotype-based approach can increase prediction ability, but that the knowledge of the genetic architecture of grain yield might not have significant consequence on genomic-assisted selection.
La Trobe University
Antony,Gendall, Hans, Daetwyler, Matthew, Hayden, , , , , , , , , , , , , , , , , , , , , , , ,
Wheat stem (Sr), leaf (Lr) and stripe (Yr) rust pathogens are among the most destructive fungal diseases threatening global wheat production. We utilized 2300 wheat accession including worldwide landraces, cultivars, breeding materials and 341 synthetic accessions backcrossed with three widely grown Australian cultivars (Annuello, Yitpi and Correll) to investigate rust resistance under wide environmental conditions. The germplasm was genotyped with 90K SNP chip, and was phenotyped for two seasons in three different environments against Sr and Lr and in four different environments against Yr. Different environments for each trait showed significant correlation with mean r values of 0.53, 0.23 and 0.66 for Lr, Sr and Yr; respectively. Single-trait genome wide association (GWAS) revealed several environment-specific QTL and multi-environmental QTL distributed on all chromosomes except 6D. Multi-trait GWAS confirmed a cluster of Yr QTL on chromosome 3B (within 8.3 cM) as well as a QTL for Sr and Lr on chromosome 3D. Linkage disequilibrium and comparative mapping showed that at least three Yr QTL exists within the 3B cluster including the durable rust resistance gene Sr2/Yr30. The same region was effective against Sr resistance but did not pass the stringent significant threshold in two environments. The 3D QTL was found mainly in the synthetic germplasm with Annuello background which is known to carry the Ag. elongatum 3D translocation carrying Sr24/Lr24 resistance gene. Interestingly, estimating the SNP effect using BayesR method showed that the correlation among the highest 5% QTL effects across environments were lower than that for the small effect QTL with differences in r values of 0.25 and 0.2 for Lr and Yr respectively. These results indicate the importance of small effect QTL that cannot be captured using GWAS in achieving durable rust resistance. The detected QTL in this study are useful resources for improving bread wheat resistance to rust diseases.
Mohamed 5th University / ICARDA
Samir,Alahmad, Ayed, Al-Abdallat, Lee, Hickey, Abdelkarim, Filali-Maltouf, Bouchra, Belkadi, Filippo, Maria Bassi, , , , , , , , , , , , , , , , , ,
Durum wheat (Triticum durum Desf.) is a major cereal crop grown globally. The terminal reduced moisture and heat occurring at the flowering phase are among the main constraints to its production. The molecular basis of tolerance to these threats remains mostly unknown. A subset of 100 genotypes derived from a collection of 384 accessions originating from different countries were investigated for their root growth and architecture under water-limited and well-watered treatments. Two protocols were used, "clear pot" for seminal root angle and "pasta strainer" for mature root angle evaluation. This study reveals that root architecture did not change depending on water treatment. A genotypic variation in root angle was found and two categories of root types were identified: genotypes with (i) superficial and (ii) deep rooting systems. In order to investigate the impact of each root type on yield, all genotypes were tested in the field at multiple locations and under different water regimes. The same set was also tested for heat tolerance in the field under rainfed conditions. Heat was imposed by placing a polytunnel at flowering time to raise the temperature of 10 degrees. The yield, thousand kernel weight and grain number per spike, were evaluated and compared to assess grain fertility, considered as a key trait of heat tolerance. The complete set was genotyped and a genome scan using 8173 SNPs markers developed by 35K Axiom array allowed to identify the genomic regions influencing drought and heat adaptation mechanisms. The pyramiding of this genomic regions could lead to an improved resilience to climate change and increase durum wheat productivity.
Chris K.,S?rensen, Rodrigo, Labouriau, Annemarie F., Justesen, Mogens S., Hovm?ller, , , , , , , , , , , , , , , , , , , , , ,
Host vernalisation and temperature strongly affect the susceptibility of winter crops to pathogenic fungi. However, how the interaction of these environmental factors influence host susceptibility to Puccinia striiformis, the yellow (stripe) rust fungus, is poorly understood. An experimental system was developed to examine the effect of vernalisation, temperature regime (standard; 18 day/12 night ?C and low; 12 day/6 night ?C) and plant growth (seedling and adult plant stages) on changes in susceptibility of agronomically important winter wheat and triticale genotypes to P. striiformis races ('Warrior' and 'Kranich') highly predominant in several European countries. Host genotypes exposed to prolonged periods of low temperature, termed vernalisation, reduced disease susceptibility on specific winter host genotypes, although its effect differed considerably by the temperature regime and the P. striiformis race deployed. The influence of vernalisation on host susceptibility was more apparent at low temperature for the 'Warrior' race and at standard temperature for the 'Kranich' race. Triticale genotypes inoculated with the 'Kranich' race were particularly affected by the influence of vernalisation and temperature regime by displaying a shift towards reduced susceptibility at standard temperature. The effect of plant growth stage, i.e., vernalised seedlings versus adult plants, was most evident for the 'Warrior' race at standard temperature and at low temperature for the 'Kranich' race by revealing a lower infection type at the adult plant stage. The research findings presented here contributed to a better understanding of the role of environmental factors in host susceptibility. This, in fact, will aid in the development of more efficient early-warning systems and disease management strategies to the yellow rust fungus and in the decision making for the deployment of winter wheat and triticale genotypes.
Research Center of Agricultural and Development in Northwest Semi-arid regions of Tunisia
Afef,OTHMANI, Olfa, SLAMA-AYED, Hajer, SLIM-AMARA, Mongi, BEN YOUNES, , , , , , , , , , , , , , , , , , , , , ,
Eleven durum wheat (Triticum durum Desf.) genotypes were screened to select for drought-tolerance under in vitro immature embryos culture. Drought stress is induced by using five PEG concentrations (0, 200, 270, 295 and 310 g/l of PEG 6000). Results showed, for all studied traits, significant differences among PEG treatments and genotypes. In fact, increasing PEG concentration decreases relative growth rate, callus water content, relative water content, in vitro tolerance and relative tolerance. Biplot analysis indicated that the first two PCs (principal components 1 and 2) explain 70.5 % and showed that Karim, Mahmoudi and Om Rabiaa are respectively the most drought tolerant varieties tested, however, Ben Bechir, Maghrbi and Nasr were the most sensitive.
Northwest A&F University
Dejun,Han, Jia, Guo, Manuel, Spannagl, Jianhui, Wu, Aizhong, Cao, Peidu, Chen, IWGSC, , Lili, Huang, Jun, Guo, Klaus, Mayer, Zhensheng, Kang, , , , , , , ,
Wheat cultivation in many regions faces threats by devastating fungal infections. However, wheat cultivar 92R137 shows resistance to Puccinia striiformis infection. To isolate the stripe rust resistance gene Yr26, an integrated transcriptomic and comparative genomics approach was undertaken. Near-isogenic lines of wheat (carrying Yr26 or not) infected with two Puccinia striiformis f. sp. tritici (Pst) (Virulence or avirulence to Yr26) were analysed in a dual detailed time series RNA-seq study. The emerging IWGSC refseq v1.0 genome assembly sequence serves as a valuable template and was also used for comparative genomics studies of the gene candidate region with the genome sequences of close relatives and wheat progenitors. Using bulked segregant analysis (BSA) to identify polymorphic SNPs between parent and resistant DNA (R-bulk) and susceptible DNA (S-bulk), flanking markers for Yr26 were identified. These two markers were mapped to the Chinese spring reference genome sequence, spanning a region of about 250 kb. The synteny analysis of this candidate region in CS chr1B with chr1A, chr1D, Wild Emmer Wheat (Td_chr1A and Td_chr1B) and Barley (chr1H) identified three candidate Yr26 genes. To detect gene candidates a dual time series RNA-seq analysis was performed. Genes differently expressed between rust susceptible (NIL-S) host lines and rust resistant (NIL-R) lines, carrying the Yr26 candidate gene were analysed. Both lines were inoculated with Pst carrying different avirulence factors (Pst-CYR32 and Pst-V26), compatible or incompatible with the corresponding wheat lines. Differential gene expression analysis (DEG) between compatible and incompatible interaction revealed DEGs in the wheat genome and in the Pst genome. From a network analysis of both wheat and Pst genes, we inferred connected co-expressed modules. Resulting modules showed particular enrichments for disease resistance, defense response to fungus and cell wall components.
Anvar,Jalilov, Zubaida, Kavrakova, Menu, Mamadyusufova, Botirov, Muhiddin, , , , , , , , , , , , , , , , , , , , , ,
The wild relatives of wheat, the genus Aegilops is of great interest for breeding. Many species of the genus Aegilops are distinguished by such valuable properties as resistance to rust diseases, drought resistance, and salt tolerance.
The evaluation of local wheat varieties on resistance to yellow rust showed that local varieties showed high resistance to the pathogen and were amazed from 0 to 10 %. Evaluation of Aegilops species for resistance to yellow and brown rust, showed that the species Aegilops triunciales showed high resistance to yellow and brown rust, except Ae. triunciales, collected in the Rudaki district and showed moderate resistance to brown rust - 20%. The view of the Aegilops cylindrical collected in the Rudakinsky district showed a moderate resistance to yellow rust and a high resistance to brown rust. View Aegilops tauschii, collected in the Rudakinsky district had a high resistance to yellow and brown rust. Species Aegilops crassa to yellow and brown rust showed a reaction from moderate resistance - 30% to moderate susceptibility - 40%. As a result of the studies to assess the resistance of wheat varieties in Central Tajikistan, the cultivars Jaldak, Safedaki Gorchivin and Viyod, which had high resistance to yellow and brown rust, as well as Pamir and Surkhak varieties, showed moderate resistance.
Distinct varieties of wheat with high and moderate resistance to the pathogen of yellow rust can be used as parental forms for breeding new varieties of wheat. Studies on assessing the resistance of Aegilops species have shown that the species Aegilops triunciales has a high resistance to the pathogen of yellow rust. Species of Aegilops tauschii and Aegilops crassa, collected from the Hissar salt source, had moderate resistance to the pathogen. These species of Aegilops can be used in the selection of new varieties of wheat.
Ayub Agricultural Research Institute, Faisalabad
Shakra,Jamil, , , , , , , , , , , , , , , , , , , , , , , , , , , ,
Different biotic and abiotic stresses are hampering wheat yield across different geographic regions. Among biotic stresses, wheat rusts are principal cause of yield reduction. Whereas among abiotic stresses, drought is the principle cause of reduction in growth and lowering yield potential. So developing rust resistance and drought tolerance in wheat germplasm is needed, which requires assessment of genetic potential of current cultivars against these stresses to identify variation among existing germplasm. Screening of genotypes under naturally prevailing races of rust species is the better and inexpensive approach. In the present study 65 genotypes including five checks (AARI-11, Chakwal- 50, Aas- 11, Morocco and Galaxy-13) were evaluated for adult plant response to wheat rusts and water deficit conditions. Experimental material was planted in four blocks each having new entries along with repetition of five checks in augmented design. Data was recorded on morphological traits including plant height, peduncle length, spike length, productive tillers per meter, flag leaf area, number of spikelet per spike, grains per spike, single head weight, 1000 grain weight, days to maturity and grain yield per acre. Significant variation was observed among genotypes for all the studied traits. On the basis of performance G39 and G36 were better than commercial drought check Chakwal-50 in almost all the traits. However rust screening under natural rust infestation revealed that although Morocco showed susceptible (S) response yet only six genotypes were susceptible to yellow rust whereas all others were resistant. In case of leaf rust 29 were completely resistance, 25 were moderately resistant, seven were moderately susceptible and only four were completely susceptible to currently active races of leaf rust. However, in the case of stem rust, 61 genotypes showed complete resistance to stem rust, two showed moderately resistance and two were moderately susceptible. Information obtained from this study would be favorable for breeding rust resistant and drought tolerant cultivars.
Wheat Research Institute, Ayub Agricultural Research Institute,Faisalabad,Pakistan
Mehvish,Makhdoom, Javed, Ahmad, Makhdoom, Hussain, Iqra, Ghafoor, , , , , , , , , , , , , , , , , , , , , ,
Wheat crop is facing immense losses each year owing to climate change, eventually being major threat to global food security. So, the objective of the present study was to screening of advance lines under drought and heat stress conditions. In following study, 30 advance lines of wheat along with four checks(Faislabad-08, Millat-11, Galaxy-13 and ujala16) with three treatments (heat, drought, normal) were tested for different morphological (days to heading, plant height, days to maturity, biomass,1000 grain weight and grain yield) and physiological (canopy temperature at vegetative & reproductive stage, NDVI vegetative & reproductive), parameters. Biplot analysis depicted that V2, V3, V8, V14, V19, V25, and V30 showed the highest OP vector for grain yield in drought environment. Whereas, under heat conditions, V3, V4, V5, V10, V11, and V12 displayed their maximum longest vector for grain yield. Correlation analysis depicted that grain yield had non-significant correlation with canopy temperature (vegetative stage), normalized difference vegetation index (vegetative stage) canopy temperature (reproductive stage), plant height, days to heading and days to maturity under heat stress environment, while it had significant association with biomass and thousand grain weight. Under drought environment, grain yield had positive and significant correlation with biomass while on the other hand it had negative but significant association with normalized difference vegetation index (reproductive stage) and canopy temperature (reproductive stage). Best performing lines could be efficiently exploited in research programs to evade the perilous impact of climate change.
Plant Pathology Research Institute
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Leaf rust resistance genes Lr9 and Lr19 were previously highly effective against the most predominant races of Puccinia triticina in Egypt. In 2015/2016 growing season, susceptible field reaction was recorded on these two genes where rust severity reached about 40S for Lr9 and 5S for Lr19 under Egyptian field conditions at four locations i.e. El-Behira, El-Minufiya, El-Qalubiya and El-Fayom governorates. Eight leaf rust field samples were collected from these governorates (four from each of Lr9 and Lr19). Forty single isolates were derived from the collected samples of Lr9 and Lr19 (each with 20 isolates). Eight pathotypes were identified from Lr9 and only two pathotypes were identified from Lr19. The most frequent pathotypes virulent to Lr9 were KTSPT (30%) followed by TTTMS (25%). Moreover, the other pathotypes ranged from 5 to 10%. Whereas, the most frequent pathotype virulent to Lr19 was CTTTT (85%) and the lowest PKTST was 15%. Pathotypes i.e. PRSTT, NTKTS and TTTMS identified from Lr9 were more aggressive on most of the tested leaf rust monogenic lines, as they were virulent to 36, 35 and 35 lines, respectively from a total of 39 lines. The two pathotypes; PKTST and CTTTT identified from Lr19 were virulent to 36 and 35 lines, respectively. Moreover, leaf rust pathotypes i.e. NPTNK and PRSTT from Lr9 and PKTST from Lr19 were the most aggressive on the tested wheat cultivars at seedling stage. The Lr2a was the most effective leaf rust resistance genes against the tested pathotypes at adult plant stage. Wheat cultivars Misr 1, Misr 2 and Nubariya 1 were the most resistant cultivars against the tested pathotypes at adult plant stage.