CREA-Research Centre for Cereal and Industrial Crops
Elisabetta Mazzucotelli, Oadi Matny, Antonietta Saccomanno, Raffaella Battaglia, Francesca Desiderio, Agata Gadaleta, Nicola Pecchioni, Pasquale De Vita, Giovanni Laido, Luigi Cattivelli, Brian Steffenson
The recent emergence of new widely virulent and aggressive strains of rusts (particularly stripe and stem rust) is threatening Italian durum wheat (Triticum turgidum L. var. durum) production, especially under the trend of higher temperature and humidity. A big effort has been undertaken to explore the genetic variability for resistance to these fungal pathogens and discovering novel resistance genes. In particular, a wide set of tetraploid wheat lines was genotyped with several thousands of SNP markers and used for association mapping. This large collection consisted of a group of durum wheat cultivars, produced from the beginning of the last century up to now, a collection of wild emmer wheats (T. dicoccoides), and lines belonging to other wild and domesticated tetraploid subspecies, as a large untapped source of genetic diversity. In a tight cooperation with the University of Minnesota, this collection was evaluated for reaction to several races of stem and stripe rust pathogens in both controlled greenhouse and field conditions. Among the genotypes belonging to the collection are parents of segregating populations which were used for the validation of mapping results. Novel resistance loci were identified, that can be incorporated into new durum varieties through breeding programs. The QTLs found in this study, together with those available in literature, were projected to the recently sequenced durum wheat genome in order to define more precisely the chromosome regions and candidate genes involved in resistance to rusts. Lines which were resistant to multiple races of rust pathogens were also found among both T. dicoccoides and durum wheat cultivars as a source of resistance genes, whose cloning will be undertaken based on the results here obtained.
This study was supported by the Italian Ministry of Foreign Affairs and International Cooperation, with the special grant RES-WHEAT.
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.
State Key Laboratory of Crop Stress Biology for Arid Areas and College of Plant Protection, Northwest A&F University, Yangling
Lijing Pang, Pu Yuan, Shoujun Hu, Jie Liu, Zhensheng Kang
Pathogens, whatever their types, develop at the expense of the nutrients generated by host and it is largely assumed that classical sources turn into sinks when colonized by pathogens. Sugar appears to be the major carbon and energy source transferred from the host to pathogens. Uptake, exchanges and competition for sugar, at biotrophic interfaces, are controlled by membrane transporters and their regulation patterns are essential in determining the outcome of plant-fungal interactions. However, mechanisms of transport and transporters involved in carbon partitioning between organisms are still poorly understood.
In this study, a wheat sugar transporter protein (STP) gene, TaSTP1, was cloned from a wheat-Puccinia striiformis f. sp. tritici (Pst) interaction cDNA library. Transcripts of TaSTP1 were up-regulated in wheat leaves that were infected by Pst or had experienced exogenous ABA and certain abiotic treatments. Heterologous mutant complementation in Saccharomyces cerevisiae revealed that TaSTP1 transports a broad-spectrum monosaccharides including glucose, fructose, mannose and galactose. Transient expression in Nicotiana benthamiana and Arabidopsis protoplasts suggested that TaSTP1 is localized in plasma membrane. Yeast two hybrid and bimolecular fluorescence complementation (BiFC) validated oligomerization of TaSTP1. Knocking down TaSTP1 using the barley stripe mosaic virus-induced gene silencing system reduced the susceptibility of wheat to the Pst virulent pathotype CYR31. Hyphal abnormality was significantly observed in VIGS plants. These results suggest that TaSTP1 may directly or indirectly participate in sugar transport in the wheat-Pst interactions and exert influence on suagr supply of Pst.
Ayub Agricultural Research Institute, Faisalabad
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.
Ethiopian Institute of Agricultural Research
Information about changes associated with advances in crop breeding is essential for understanding yield-limiting factors and developing new strategies for future breeding programmes. Thirty-six durum wheat varieties released since 1966 were evaluated in three replications of the Randomized Complete Design at Debre Zeit and Akaki, Ethiopia during the 2016 cropping season to estimate the amount of genetic gain made over time in grain yield potential, yield-associated traits and in protein content. Analysis of variance revealed significant differences among varieties for all 16 quantitative traits, protein content and protein harvest in Kg ha-1 at each of the locations. Grain yield varied between 1.66t ha-1 for Arendato released in 1966 to 3.90t ha-1 for Megenagna released in 2012 with mean of 2.952t ha-1 at Debre Zeit. At Akaki yield range was between 2.45 and 5.04t ha-1 with mean of 3.992t ha-1. 25 varieties surpassed Arendato (3.754t ha-1) at this location. In the combined ANOVA significant difference between the varieties was observed only for spike length, spikelets spike-1, grains spikelet, grains spike-1, plant height, days to flowering, thousand grain weight and hectoliter weight. Varieties specifically adapted to only one of the locations, widely adapted varieties and varieties not adapted to any of the locations were identified. Regression analysis revealed that grain yield has increased by 22kg ha-1 year-1 since 1966; an increase of 40.6% over yield in 1966. This was accompanied with a significant decline of 11.4% in spike length, 6.7% in spikelets spike-1, 17.9% in protein content and 31.2% in protein yield ha-1 and a significant increase of 41.1% in grains spikelet-1, 32.9% in number of grains spike-1, 22.3% in thousand grain weight, 17.8% in grain filling period, 23.9% in seed growth rate, 40.1% in grain yield production rate, 7.9% in harvest index.
Seed and Plant Improvement Institute, Agricultural Research, Education and Extension Organization, Karaj, Iran.
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Stripe rust of wheat, caused by Puccinia striiformis f. sp. trirtici (Pst) is an important disease in many parts of Iran. Over last two decades several epidemics have occurred in Iran causing the breakdown of widely utilized sources of resistance in wheat cultivars. Fifty isolates were collected from different parts of Iran during 2017. Eight isolates of Pst. from 2017 have been processed to date for race analysis. Infection types were assessed on a 0-9 scale 16 and 18 days after inoculation using a scale similar to that described by McNeal et al. (1971). Infection types (ITs) 7 to 9 were regarded as virulent (susceptible) and lower than 7 were avirulent. Pathotypes 102E158A+,Yr27; 6E158A+,Yr27; 102E158A+,Yr27; 166E154A+,Yr27; 38E174A+; 38E158A+,Yr27; 238E190A+,Yr27 and 38E190A+,Yr27 were identified. Pathotype 238E190A+,Yr27+ (from West of Iran) was more aggressive during this study. Plants with Yr1, Yr4, Yr5, Yr10, Yr15, Yr24 and YrSP were resistant to all pathotypes. Pathotypes with virulence on plant with gene/s Yr2, Yr6, Yr7, Yr8, Yr9, Yr25, Yr26, Yr27, Yr32, YrSD, YrSU, YrND and YrA were more common. Seedling tests of Iranian wheat cultivars to race 238E190A+,Yr27+ showed that the new released cultivars that included Parsi, Baharan, Bahar, Pishgam, Zareh, Urom, Maihan, Dena, Haydarei and Shabrang were resistant to the new aggressive race with virulence on plants with Yr27.
The University of Queensland, Queensland Alliance for Agriculture and Food Innovation (QAAFI)
Naveenkumar,Athiyannan, Sambasivam, Periyannan, Olga, Afanasenko, Olga, Mitrofanova, Gregory, Platz, Elizabeth, Aitken, Rod, Snowdon, Evans, Lagudah, Lee, Hickey, Kai, Voss-Fels, , , , , , , , , ,
Leaf rust (LR) is an important wheat disease and deployment of resistant cultivars is the most viable strategy to minimise yield losses. We evaluated a diversity panel of 295 bread wheat accessions from the N. I. Vavilov Institute of Plant Genetic Resources (VIR), St Petersburg, Russia for LR response and performed genome-wide association studies (GWAS) using 10,748 polymorphic DArT-seq markers. The diversity panel was evaluated at the seedling and adult plant growth stages using three prevalent Australian P. triticina pathotypes. GWAS applied to 11 phenotypic data sets identified a total of 52 significant marker-trait associations representing 31 quantitative trait loci (QTL). Among them, 29 QTL were associated with adult plant resistance (APR). Of the 31 QTL, 13 were considered potentially new loci, whereas 4 co-located with previously catalogued Lr genes and 14 aligned to regions reported in other GWAS and genomic prediction studies. One seedling LR resistance QTL located on chromosome 3A showed pronounced levels of linkage disequilibrium among markers (r2 = 0.7), indicative of a high allelic fixation. Subsequent haplotype analysis for this region found 7 haplotype variants, of which 2 were strongly associated with LR resistance at the seedling stage. Similarly, analysis of an APR QTL on chromosome 7B revealed 22 variants, of which 4 were associated with resistance at the adult-plant stage. Most of the lines in the diversity panel carried 10 or more combined resistance-associated marker alleles, highlighting the potential of allele stacking for long-lasting resistance.
1,3 Colegio de Postgraduados-Fitosanidad, Campus Montecillo, Texcoco, 56230, Estado de M?xico, M?xico
Julio Huerta-Espino, Ravi P. Singh, Caixia Lan, Sridhar Bhavani, Reyna I. Rojas-Martínez, Ignacio Benitez-Riquelme, Cristian Nava-Díaz, Mandeep Singh Randhawa
Leaf rust and stripe rust caused by the fungi Puccinia triticina and P. striiformis f. sp. tritici, respectively, are important diseases of wheat and represent a significant threat in most wheat producing regions worldwide. Growing resistant varieties and the identification and characterization of new sources of resistance are necessary to combat the threat from the evolving pathogen population. Bread wheat (Triticum aestivum L.) line 'Kijil' developed at CIMMYT showed adult plant resistance (APR) to leaf rust (LR) and stripe rust (YR). The genetic basis of the resistance was investigated using 198 recombinant inbred lines (RILs) derived from the cross of susceptible Apav#1 and resistant Kijil. Field phenotyping of parents and RILs were conducted at El Batón, Toluca and Ciudad Obregon, Mexico during 2016 and 2017. Pearson correlation coeffcients (P< 0.0001) were high for disease severities between two years of evaluations: LR (r= 0.90) and YR (r= 0.83). Correlations (r= 0.30-0.76) were also significant between LR and YR in all environments. Genetic analyses indicated that 3 to 5 genes of additive effects governed resistance to both rusts. RILs carrying the pleiotropic APR gene Lr46/Yr29/Sr58 showed 23 and 41% of disease severity for LR and YR respectively, whereas lines lacking it had 55 and 78% severities. RILs positive for Sr2/Yr30 showed 66% YR severity, whereas those negative displayed 78%. In addition, lines carrying the race-specific gene Yr17/Sr38 showed 28% YR severity in contrast to non-carriers that displayed 78% severity. We conclude that Kijil possesses a complex nature of resistance.
The University of Georgia (UGA)
Suraj Sapkota, James Buck, Jerry Johnson, John Youmans
Leaf rust disease, caused by the fungal pathogen Puccinia triticina, is a major biotic constraint of wheat production worldwide. Genetic resistance is the most effective, economic, and environmentally safe method to control and reduce losses caused by this disease. More than 70 leaf rust resistance genes have been identified and mapped to specific chromosomes; however, continuous evolution of new leaf rust races requires constant search for new sources of resistance with novel QTL/genes. The objectives of this study were to identify sources of resistance, and to map genomic loci associated with leaf rust resistance using genome wide association study (GWAS) approach. Phenotypic evaluation of 297 spring wheat genotypes against a prevalent race of leaf rust in Georgia revealed that most of the genotypes were susceptible, and only 24 genotypes were found resistant. Furthermore, GWAS detected 10 markers on chromosomes 2A, 2B, 6A, 7A, and 7B significantly associated with leaf rust resistance. A marker on chromosome 7AS was identified revealing a novel genomic region associated with leaf rust resistance. The new identified sources of resistance and QTL could be used in wheat breeding programs to improve leaf rust resistance.
State Key Laboratory of Crop Stress Biology for Arid Areas and College of Plant Protection, Northwest A&F University
Yuan Tian, Yan Meng, Hengbo Ma, Lili Huang, Zhensheng Kang
Stripe rust, caused by Puccinia striiformis Westend f.sp. tritici, is currently one of the most prevalent and damaging disease on wheat. Up to now, some genes in wheat which are resistant to wheat stripe rust have been cloned, but little is known about the corresponding avirulence gene according to the gene-for-gene hypothesis. A population containing 118 progeny isolates population acquired by selfing an isolate, PL17-7, with virulence to Yr26 was derived. Seventy-two progeny isolates were different in genotype depending on 92 simple sequence repeat (SSR) markers. The progeny population segregated for avirulence to Yr6 at one locus (3 avirulent :1 virulent ratio). The parental isolate and 72 of 118 progeny isolates were resequenced to find candidate avirulence genes corresponding to Yr6. Overall, 7.6 million reads per sample were obtained and mapped to the draft genome of a Chinese Pst isolate CY32. The median depth of coverage was 63.6 fold. For each isolate, between 97.6% and 98.1% of the sequence reads were mapped to the race CY32 genome, which covered between 87.3% and 95.4% of the reference genome bases. An average of 97357 single nucleotide polymorphisms (SNP) per isolate was found, which covered 8.1% of the reference genome. Different SNPs and Indels were found when isolates virulent and avirulent to wheat cultivar containing Yr6 were grouped into two groups. Though screening discrepant SNP and indel in these two groups, candidate avirulence genes corresponding to Yr6 may be found.