Publications by authors named "Roi Ben-David"

18 Publications

  • Page 1 of 1

Assessing adaptive requirements and breeding potential of spelt under Mediterranean environment.

Sci Rep 2021 Mar 30;11(1):7208. Epub 2021 Mar 30.

Department of Vegetable and Field Crops, Institute of Plant Sciences, Agricultural Research Organization (ARO)-Volcani Center, 7528809, Rishon LeZion, Israel.

The rising demand for spelt wheat (Triticum aestivum ssp. spelta) as a high-value grain crop has raised interest in its introduction into non-traditional spelt growing areas. This study aimed to assess adaptive constrains of spelt under short Mediterranean season. At first screening of a wide spelt collection for phenology and allelic distribution at the photoperiod (PPD) and vernalization (VRN) loci was done. In addition an in-depth phenotypic evaluation of a selected panel (n = 20) was performed, including agronomically important traits and concentration of grain mineral (GMC) and grain protein (GPC) content. Results from both wide screening and in-depth in panel (group of 18 spelt lines and two bread wheat lines) evaluation shows that the major adaptive constraint for spelt under Mediterranean conditions is late heading, caused by day length sensitivity, as evident from phenology and allelic profile (PPD and VRN). All lines carrying the photoperiod-sensitive allele (PPD-D1b) were late flowering (> 120DH). Based on the panel field evaluations those consequently suffer from low grain yield and poor agronomic performances. As for minerals, GMC for all but Zn, significantly correlated with GPC. In general, GMC negatively correlated with yield which complicated the assessment of GMC per-se and challenge the claim for higher mineral content in spelt grains. The exceptions were, Fe and Zn, which did not correlate with yield. Spelt lines showing high Fe and Zn concentration in a high-yield background illustrate their potential for spelt wheat breeding. Improving spelt adaptation to Mediterranean environments could be mediated by introducing the insensitive-PPD-D1a allele to spelt wheat background. Following this breeding path spelt could better compete with bread wheat under short season with limited and fluctuating rain fall.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41598-021-86276-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8010017PMC
March 2021

Genetic improvement of wheat early vigor promote weed-competitiveness under Mediterranean climate.

Plant Sci 2021 Feb 4;303:110785. Epub 2020 Dec 4.

The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Hebrew University of Jerusalem, Rehovot 7610001, Israel. Electronic address:

Chemical weed-control is the most effective practice for wheat, however, rapid evolution of herbicide-resistant weeds threat food-security and calls for integration of non-chemical practices. We hypothesis that integration of alternative GA-responsive dwarfing genes into elite wheat cultivars can promote early vigor and weed-competitiveness under Mediterranean climate. We develop near-isogenic lines of bread wheat cultivars with GAR dwarfing genes and evaluate them for early vigor and weed-competitiveness under various environmental and management conditions to identify promising NIL for weed-competitiveness and grain yield. While all seven NILs responded to external gibberellic acid application, they exhibited differences in early vigor. Greenhouse and field evaluations highlighted NIL OC1 (Rht8andRht12) as a promising line, with significant advantage in canopy early vigor over its parental. To facilitate accurate and continuous early vigor data collection, we applied non-destructive image-based phenotyping approaches which offers non-expensive and end-user friendly solution for selection. NIL OC1 was tested under different weed density level, infestation waves, and temperatures and highlight the complex genotypic × environmental × management interactions. Our findings demonstrate the potential of genetic modification of dwarfing genes as promising approach to improve weed-competitiveness, and serve as basis for future breeding efforts to support sustainable wheat production under semi-arid Mediterranean climate.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.plantsci.2020.110785DOI Listing
February 2021

Characterization of the Barley Net Blotch Pathosystem at the Center of Origin of Host and Pathogen.

Pathogens 2019 Nov 29;8(4). Epub 2019 Nov 29.

Department of vegetables and field crops, Institute of Plant Science, Agricultural Research Organization, The Volcani Center, Rishon LeZion 7505101, Israel.

Net blotch (NB) is a major disease of barley caused by the fungus f. (), and f. (). and infect the cultivated crop () and its wild relatives ( ssp. and ssp. ). The main goal of this research was to study the NB-causing pathogen in the crop center of origin. To address this, we have constructed a (n = 15) and (n = 12) collection isolated from three barley species across Israel. Isolates were characterized genetically and phenotypically. Aggressiveness of the isolates was determined based on necrotrophic growth rate on detached leaves of barley. In addition, isolates were genetically characterized by the mating type, followed by phylogenetic analysis, clustering them into seven groups. The analysis showed no significant differentiation of isolates based on either geographic origin, host of origin or form ( vs. ). Nevertheless, there was a significant difference in aggressiveness among the isolates regardless of host species, geographic location or sampling site. Moreover, it was apparent that the isolates derived from wild hosts were more variable in their necrotrophic growth rate, compared to isolates sampled from cultivated hosts, thereby suggesting that NB plays a major role in epidemiology at the center of barley origin where most of the diversity lies. has significantly higher necrotrophic and saprotrophic growth rates than , and for both a significant negative correlation was found between light intensity exposure and growth rates.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/pathogens8040275DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6963742PMC
November 2019

The Israeli-Palestinian wheat landraces collection: restoration and characterization of lost genetic diversity.

J Sci Food Agric 2020 Aug 18;100(11):4083-4092. Epub 2019 Jul 18.

Department of Vegetables and Field Crop, Institute of Plant Sciences, Agricultural Research Organization, Volcani Center, Rishon LeZion, Israel.

Background: For over a century, genetic diversity of wheat worldwide was eroded by continual selection for high yields and industrial demands. Wheat landraces cultivated in Israel and Palestine demonstrate high genetic diversity and a potentially wide repertoire of adaptive alleles. While most Israeli-Palestinian wheat landraces were lost in the transition to 'Green Revolution' semi-dwarf varieties, some germplasm collections made at the beginning of the 20th century survived in gene banks and private collections worldwide. However, fragmentation and poor conservation place this unique genetic resource at a high risk of genetic erosion. Herein, we describe a long-term initiative to restore, conserve, and characterize a collection of Israeli and Palestinian wheat landraces (IPLR).

Results: We report on (i) the IPLR construction (n = 932), (ii) the historical and agronomic context to this collection, (iii) the characterization and assessment of the IPLR's genetic diversity, and (iv) a data comparison from two distinct subcollections within IPLR: a collection made by N. Vavilov in 1926 (IPLR-VIR) and a later one (1979-1981) made by Y. Mattatia (IPLR-M). Though conducted in the same eco-geographic space, these two collections were subjected to considerably different conservation pathways. IPLR-M, which underwent only one propagation cycle, demonstrated marked genetic and phenotypic variability (within and between accessions) in comparison with IPLR-VIR, which had been regularly regenerated over ∼90 years.

Conclusion: We postulate that long-term ex situ conservation involving human and genotype × environment selection may significantly reduce accession heterogeneity and allelic diversity. Results are further discussed in a broader context of pre-breeding and conservation. © 2019 Society of Chemical Industry.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jsfa.9822DOI Listing
August 2020

The AvrPm3-Pm3 effector-NLR interactions control both race-specific resistance and host-specificity of cereal mildews on wheat.

Nat Commun 2019 05 23;10(1):2292. Epub 2019 May 23.

Department of Plant and Microbial Biology, University of Zurich, 8008, Zurich, Switzerland.

The wheat Pm3 resistance gene against the powdery mildew pathogen occurs as an allelic series encoding functionally different immune receptors which induce resistance upon recognition of isolate-specific avirulence (AVR) effectors from the pathogen. Here, we describe the identification of five effector proteins from the mildew pathogens of wheat, rye, and the wild grass Dactylis glomerata, specifically recognized by the PM3B, PM3C and PM3D receptors. Together with the earlier identified AVRPM3, the recognized AVRs of PM3B/C, (AVRPM3), and PM3D (AVRPM3) belong to a large group of proteins with low sequence homology but predicted structural similarities. AvrPm3 and AvrPm3 are conserved in all tested isolates of wheat and rye mildew, and non-host infection assays demonstrate that Pm3b, Pm3c, and Pm3d are also restricting the growth of rye mildew on wheat. Furthermore, divergent AVR homologues from non-adapted rye and Dactylis mildews are recognized by PM3B, PM3C, or PM3D, demonstrating their involvement in host specificity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41467-019-10274-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6533294PMC
May 2019

Genome Based Meta-QTL Analysis of Grain Weight in Tetraploid Wheat Identifies Rare Alleles of GRF4 Associated with Larger Grains.

Genes (Basel) 2018 Dec 17;9(12). Epub 2018 Dec 17.

School of Plant Sciences and Food Security, Tel Aviv University, Tel Aviv 6997801, Israel.

The domestication and subsequent genetic improvement of wheat led to the development of large-seeded cultivated wheat species relative to their smaller-seeded wild progenitors. While increased grain weight (GW) continues to be an important goal of many wheat breeding programs, few genes underlying this trait have been identified despite an abundance of studies reporting quantitative trait loci (QTL) for GW. Here we perform a QTL analysis for GW using a population of recombinant inbred lines (RILs) derived from the cross between wild emmer wheat accession 'Zavitan' and durum wheat variety 'Svevo'. Identified QTLs in this population were anchored to the recent Zavitan reference genome, along with previously published QTLs for GW in tetraploid wheat. This genome-based, meta-QTL analysis enabled the identification of a locus on chromosome 6A whose introgression from wild wheat positively affects GW. The locus was validated using an introgression line carrying the 6A GW QTL region from Zavitan in a Svevo background, resulting in >8% increase in GW compared to Svevo. Using the reference sequence for the 6A QTL region, we identified a wheat ortholog to OsGRF4, a rice gene previously associated with GW. The coding sequence of this gene (TtGRF4-A) contains four single nucleotide polymorphisms (SNPs) between Zavitan and Svevo, one of which reveals the Zavitan allele to be rare in a core collection of wild emmer and completely absent from the domesticated emmer genepool. Similarly, another wild emmer accession (G18-16) was found to carry a rare allele of TtGRF4-A that also positively affects GW and is characterized by a unique SNP absent from the entire core collection. These results exemplify the rich genetic diversity of wild wheat, posit TtGRF4-A as a candidate gene underlying the 6A GW QTL, and suggest that the natural Zavitan and G18-16 alleles of TtGRF4-A have potential to increase wheat yields in breeding programs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/genes9120636DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6315823PMC
December 2018

Reciprocal Hosts' Responses to Powdery Mildew Isolates Originating from Domesticated Wheats and Their Wild Progenitor.

Front Plant Sci 2018 23;9:75. Epub 2018 Feb 23.

Department of Evolutionary and Environmental Biology, Faculty of Natural Sciences, Institute of Evolution, University of Haifa, Haifa, Israel.

The biotroph wheat powdery mildew, (DC.) E.O. Speer, f. sp. Em. Marchal (), has undergone long and dynamic co-evolution with its hosts. In the last 10,000 years, processes involved in plant evolution under domestication, altered host-population structure. Recently both virulence and genomic profiling separated into two groups based on their origin from domestic host and from wild emmer wheat. While most studies focused on the pathogen, there is significant knowledge gaps in the role of wheat host diversity in this specification. This study aimed to fill this gap by exploring qualitatively and also quantitatively the disease response of diverse host panel to powdery mildew [105 domesticated wheat genotypes ( ssp. ssp. , and ) and 241 accessions of its direct progenitor, wild emmer wheat ( ssp. )]. A set of eight isolates, originally collected from domesticated and wild wheat was used for screening this wheat collection. The isolates from domesticated wheat elicited susceptible to moderate plant responses on domesticated wheat lines and high resistance on wild genotypes (51.7% of the tested lines were resistant). Isolates from wild emmer elicited reciprocal disease responses: high resistance of domesticated germplasm and high susceptibility of the wild material (their original host). Analysis of variance of the quantitative phenotypic responses showed a significant Isolates × Host species interaction [(F) < 0.0001] and further supported these findings. Furthermore, analysis of the range of disease severity values showed that when the group of host genotypes was inoculated with isolate from the reciprocal host, coefficient of variation was significantly higher than when inoculated with its own isolates. This trend was attributed to the role of major resistance genes in the latter scenario (high proportion of complete resistance). By testing the association between disease severity and geographical distance from the source of inoculum, we have found higher susceptibility in wild emmer close to the source. Both qualitative and quantitative assays showed a reciprocal resistance pattern in the wheat host and are well aligned with the recent findings of significant differentiation into wild-emmer and domesticated-wheat populations in the pathogen.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fpls.2018.00075DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5829517PMC
February 2018

Distinct domains of the AVRPM3 avirulence protein from wheat powdery mildew are involved in immune receptor recognition and putative effector function.

New Phytol 2018 04 17;218(2):681-695. Epub 2018 Feb 17.

Department of Plant and Microbial Biology, University of Zürich, Zollikerstrasse 107, 8008, Zürich, Switzerland.

Recognition of the AVRPM3 avirulence protein from powdery mildew by the wheat PM3A/F immune receptor induces a hypersensitive response after co-expression in Nicotiana benthamiana. The molecular determinants of this interaction and how they shape natural AvrPm3 allelic diversity are unknown. We sequenced the AvrPm3 gene in a worldwide collection of 272 mildew isolates. Using the natural polymorphisms of AvrPm3 as well as sequence information from related gene family members, we tested 85 single-residue-altered AVRPM3 variants with PM3A, PM3F and PM3F (modified for improved signaling) in Nicotiana benthamiana for effects on recognition. An intact AvrPm3 gene was found in all analyzed isolates and the protein variant recognized by PM3A/F occurred globally at high frequencies. Single-residue alterations in AVRPM3 mostly disrupted, but occasionally enhanced, the recognition response by PM3A, PM3F and PM3F . Residues enhancing hypersensitive responses constituted a protein domain separate from both naturally occurring polymorphisms and positively selected residues of the gene family. These results demonstrate the utility of using gene family sequence diversity to screen residues for their role in recognition. This approach identified a putative interaction surface in AVRPM3 not polymorphic in natural alleles. We conclude that molecular mechanisms besides recognition drive AvrPm3 diversification.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/nph.15026DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6175116PMC
April 2018

Wild emmer genome architecture and diversity elucidate wheat evolution and domestication.

Science 2017 07;357(6346):93-97

University of Bologna, Bologna, Italy.

Wheat ( spp.) is one of the founder crops that likely drove the Neolithic transition to sedentary agrarian societies in the Fertile Crescent more than 10,000 years ago. Identifying genetic modifications underlying wheat's domestication requires knowledge about the genome of its allo-tetraploid progenitor, wild emmer ( ssp. ). We report a 10.1-gigabase assembly of the 14 chromosomes of wild tetraploid wheat, as well as analyses of gene content, genome architecture, and genetic diversity. With this fully assembled polyploid wheat genome, we identified the causal mutations in () genes controlling shattering, a key domestication trait. A study of genomic diversity among wild and domesticated accessions revealed genomic regions bearing the signature of selection under domestication. This reference assembly will serve as a resource for accelerating the genome-assisted improvement of modern wheat varieties.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1126/science.aan0032DOI Listing
July 2017

AvrPm2 encodes an RNase-like avirulence effector which is conserved in the two different specialized forms of wheat and rye powdery mildew fungus.

New Phytol 2017 Feb 9;213(3):1301-1314. Epub 2016 Dec 9.

Department of Plant and Microbial Biology, University of Zürich, Zürich, 8008, Switzerland.

There is a large diversity of genetically defined resistance genes in bread wheat against the powdery mildew pathogen Blumeria graminis (B. g.) f. sp. tritici. Many confer race-specific resistance to this pathogen, but until now only the mildew avirulence gene AvrPm3 that is recognized by Pm3a/f was known molecularly. We performed map-based cloning and genome-wide association studies to isolate a candidate for the mildew avirulence gene AvrPm2. We then used transient expression assays in Nicotiana benthamiana to demonstrate specific and strong recognition of AvrPm2 by Pm2. The virulent AvrPm2 allele arose from a conserved 12 kb deletion, while there is no protein sequence diversity in the gene pool of avirulent B. g. tritici isolates. We found one polymorphic AvrPm2 allele in B. g. triticale and one orthologue in B. g. secalis and both are recognized by Pm2. AvrPm2 belongs to a small gene family encoding structurally conserved RNase-like effectors, including Avr from B. g. hordei, the cognate Avr of the barley resistance gene Mla13. These results demonstrate the conservation of functional avirulence genes in two cereal powdery mildews specialized on different hosts, thus providing a possible explanation for successful introgression of resistance genes from rye or other grass relatives to wheat.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/nph.14372DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5347869PMC
February 2017

Differentiation Among Blumeria graminis f. sp. tritici Isolates Originating from Wild Versus Domesticated Triticum Species in Israel.

Phytopathology 2016 Aug 8;106(8):861-70. Epub 2016 Jun 8.

First author: Department of Vegetables and Field Crops, Institute of Plant Sciences, ARO-Volcani Center, Bet Dagan 5025000, Israel; second and seventh authors: United States Department of Agriculture-Agricultural Research Service, Department of Plant Pathology, North Carolina State University, Raleigh 27695; third author: The Department of Plant Pathology and Microbiology, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 7610001, Israel; fourth author: Institute for Cereal Crops Improvement (ICCI), The George S. Wise Faculty for Life Sciences Tel Aviv University, Tel Aviv 69978, Israel; and fifth and sixth authors: Department of Plant and Microbial Biology, University of Zurich, Zollikerstrasse 107, CH-8008 Zurich, Switzerland.

Israel and its vicinity constitute a center of diversity of domesticated wheat species (Triticum aestivum and T. durum) and their sympatrically growing wild relatives, including wild emmer wheat (T. dicoccoides). We investigated differentiation within the forma specialis of their obligate powdery mildew pathogen, Blumeria graminis f. sp. tritici. A total of 61 B. graminis f. sp. tritici isolates were collected from the three host species in four geographic regions of Israel. Genetic relatedness of the isolates was characterized using both virulence patterns on 38 wheat lines (including 21 resistance gene differentials) and presumptively neutral molecular markers (simple-sequence repeats and single-nucleotide polymorphisms). All isolates were virulent on at least some genotypes of all three wheat species tested. All assays divided the B. graminis f. sp. tritici collection into two distinct groups, those from domesticated hosts and those from wild emmer wheat. One-way migration was detected from the domestic wheat B. graminis f. sp. tritici population to the wild emmer B. graminis f. sp. tritici population at a rate of five to six migrants per generation. This gene flow may help explain the overlap between the distinct domestic and wild B. graminis f. sp. tritici groups. Overall, B. graminis f. sp. tritici is significantly differentiated into wild-emmer and domesticated-wheat populations, although the results do not support the existence of a separate f. sp. dicocci.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1094/PHYTO-07-15-0177-RDOI Listing
August 2016

Hybridization of powdery mildew strains gives rise to pathogens on novel agricultural crop species.

Nat Genet 2016 Feb 11;48(2):201-5. Epub 2016 Jan 11.

Department of Plant and Microbial Biology, University of Zürich, Zurich, Switzerland.

Throughout the history of agriculture, many new crop species (polyploids or artificial hybrids) have been introduced to diversify products or to increase yield. However, little is known about how these new crops influence the evolution of new pathogens and diseases. Triticale is an artificial hybrid of wheat and rye, and it was resistant to the fungal pathogen powdery mildew (Blumeria graminis) until 2001 (refs. 1,2,3). We sequenced and compared the genomes of 46 powdery mildew isolates covering several formae speciales. We found that B. graminis f. sp. triticale, which grows on triticale and wheat, is a hybrid between wheat powdery mildew (B. graminis f. sp. tritici) and mildew specialized on rye (B. graminis f. sp. secalis). Our data show that the hybrid of the two mildews specialized on two different hosts can infect the hybrid plant species originating from those two hosts. We conclude that hybridization between mildews specialized on different species is a mechanism of adaptation to new crops introduced by agriculture.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/ng.3485DOI Listing
February 2016

Multiple Avirulence Loci and Allele-Specific Effector Recognition Control the Pm3 Race-Specific Resistance of Wheat to Powdery Mildew.

Plant Cell 2015 Oct 9;27(10):2991-3012. Epub 2015 Oct 9.

Institute of Plant Biology, University of Zurich, CH-8008 Zürich, Switzerland

In cereals, several mildew resistance genes occur as large allelic series; for example, in wheat (Triticum aestivum and Triticum turgidum), 17 functional Pm3 alleles confer agronomically important race-specific resistance to powdery mildew (Blumeria graminis). The molecular basis of race specificity has been characterized in wheat, but little is known about the corresponding avirulence genes in powdery mildew. Here, we dissected the genetics of avirulence for six Pm3 alleles and found that three major Avr loci affect avirulence, with a common locus_1 involved in all AvrPm3-Pm3 interactions. We cloned the effector gene AvrPm3(a2/f2) from locus_2, which is recognized by the Pm3a and Pm3f alleles. Induction of a Pm3 allele-dependent hypersensitive response in transient assays in Nicotiana benthamiana and in wheat demonstrated specificity. Gene expression analysis of Bcg1 (encoded by locus_1) and AvrPm3 (a2/f2) revealed significant differences between isolates, indicating that in addition to protein polymorphisms, expression levels play a role in avirulence. We propose a model for race specificity involving three components: an allele-specific avirulence effector, a resistance gene allele, and a pathogen-encoded suppressor of avirulence. Thus, whereas a genetically simple allelic series controls specificity in the plant host, recognition on the pathogen side is more complex, allowing flexible evolutionary responses and adaptation to resistance genes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1105/tpc.15.00171DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4682313PMC
October 2015

Effect of GA-sensitivity on wheat early vigor and yield components under deep sowing.

Front Plant Sci 2015 10;6:487. Epub 2015 Jul 10.

The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Hebrew University of Jerusalem Rehovot, Israel.

Establishment of seedlings is a key factor in achievement of uniform field stands and, consequently, stable yields. Under Mediterranean conditions, soil moisture in the upper layer is limited and seedlings may be exposed to frequent dehydration events. The presence of the Reduced height (Rht)-B1b and Rht-D1b semi-dominant dwarfing alleles results in insensitivity to gibberellin (GAI) and, hence, poor emergence from deep sowing. Introduction of alternative dwarfing genes and, thereby, preservation of the gibberellin response (GAR) and coleoptile length, contributes to better emergence from deep sowing. Initially 47 wheat cultivars carrying different Rht alleles were screened for their ability to emerge from deep sowing, and then 17 of them were selected for detailed physiological characterization in the field. The modern wheat lines containing GAI alleles showed significantly lower percentages of emergence from deep sowing than the GAR lines, i.e., 52 and 74%, respectively. Differences in early developmental stages were associated with grain yield, as indicated by a reduction of 37.3% in the modern GAI cultivars. Our results demonstrate the potential of alternative dwarfing genes for improving seedling establishment and grain yields in Mediterranean-like environments.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fpls.2015.00487DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4498040PMC
July 2015

Genetic and molecular characterization of a locus involved in avirulence of Blumeria graminis f. sp. tritici on wheat Pm3 resistance alleles.

Fungal Genet Biol 2015 Sep 9;82:181-92. Epub 2015 Jul 9.

Institute of Plant Biology, University of Zürich, Zollikerstrasse 107, 8008 Zürich, Switzerland. Electronic address:

Wheat powdery mildew is caused by the obligate biotrophic fungus Blumeria graminis f. sp. tritici. The allelic series of the wheat Pm3 gene conferring race-specific resistance against powdery mildew has been well characterized functionally, and recently the corresponding avirulence gene AvrPm3a/f triggering the specific recognition by Pm3a and Pm3f alleles was cloned. Here, we describe the genetic and molecular analysis of two additional Blumeria loci involved in the resistance mediated by the Pm3c and Pm3f alleles. We genetically identified the two loci and mapped at high resolution one locus involved in the avirulence towards both Pm3c and Pm3f. The single candidate gene Bcg1 was identified in a physical target interval of 26kb defined by flanking genetic markers. Bcg1 encodes a small secreted protein sharing structural homology with ribonucleases and belongs to a family of clustered putative effector genes under diversifying selection. We found a very good, but not complete, correlation of Bcg1 haplotypes with the phenotypes of natural isolates. Two mutants were generated that were affected in their phenotypes towards Pm3a and Pm3f but did not show any sequence polymorphism in Bcg1. Our results suggest that avirulence to Pm3 in Blumeria is determined by a complex network of genes, in which Bcg1 might have a central role as a modifier of the Pm3/AvrPm3 interactions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.fgb.2015.06.009DOI Listing
September 2015

The wheat powdery mildew genome shows the unique evolution of an obligate biotroph.

Nat Genet 2013 Sep 14;45(9):1092-6. Epub 2013 Jul 14.

Institute of Plant Biology, University of Zurich, Zurich, Switzerland.

Wheat powdery mildew, Blumeria graminis forma specialis tritici, is a devastating fungal pathogen with a poorly understood evolutionary history. Here we report the draft genome sequence of wheat powdery mildew, the resequencing of three additional isolates from different geographic regions and comparative analyses with the barley powdery mildew genome. Our comparative genomic analyses identified 602 candidate effector genes, with many showing evidence of positive selection. We characterize patterns of genetic diversity and suggest that mildew genomes are mosaics of ancient haplogroups that existed before wheat domestication. The patterns of diversity in modern isolates suggest that there was no pronounced loss of genetic diversity upon formation of the new host bread wheat 10,000 years ago. We conclude that the ready adaptation of B. graminis f.sp. tritici to the new host species was based on a diverse haplotype pool that provided great genetic potential for pathogen variation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/ng.2704DOI Listing
September 2013

Identification and characterization of a novel powdery mildew resistance gene PmG3M derived from wild emmer wheat, Triticum dicoccoides.

Theor Appl Genet 2012 Mar 8;124(5):911-22. Epub 2011 Dec 8.

Department of Evolutionary and Environmental Biology, Institute of Evolution, Faculty of Natural Sciences, University of Haifa, Mt. Carmel, Haifa, Israel.

Powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt) is one of the most important wheat diseases worldwide. Wild emmer wheat, Triticum turgidum ssp. dicoccoides, the tetraploid ancestor (AABB) of domesticated bread and durum wheat, harbors many important alleles for resistance to various diseases, including powdery mildew. In the current study, two tetraploid wheat mapping populations, derived from a cross between durum wheat (cv. Langdon) and wild emmer wheat (accession G-305-3M), were used to identify and map a novel powdery mildew resistance gene. Wild emmer accession G-305-3M was resistant to all 47 Bgt isolates tested, from Israel and Switzerland. Segregation ratios of F(2) progenies and F(6) recombinant inbred line (RIL) mapping populations, in their reactions to inoculation with Bgt, revealed a Mendelian pattern (3:1 and 1:1, respectively), indicating the role of a single dominant gene derived from T. dicoccoides accession G-305-3M. This gene, temporarily designated PmG3M, was mapped on chromosome 6BL and physically assigned to chromosome deletion bin 6BL-0.70-1.00. The F(2) mapping population was used to construct a genetic map of the PmG3M gene region consisted of six simple sequence repeats (SSR), 11 resistance gene analog (RGA), and two target region amplification polymorphism (TRAP) markers. A second map, constructed based on the F(6) RIL population, using a set of skeleton SSR markers, confirmed the order of loci and distances obtained for the F(2) population. The discovery and mapping of this novel powdery mildew resistance gene emphasize the importance of the wild emmer wheat gene pool as a source for crop improvement.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00122-011-1756-8DOI Listing
March 2012

Identification and mapping of PmG16, a powdery mildew resistance gene derived from wild emmer wheat.

Theor Appl Genet 2010 Aug 21;121(3):499-510. Epub 2010 Apr 21.

Department of Evolutionary and Environmental Biology, The Institute of Evolution, Faculty of Science and Science Education, University of Haifa, Mt. Carmel, 31905, Haifa, Israel.

The gene-pool of wild emmer wheat, Triticum turgidum ssp. dicoccoides, harbors a rich allelic repertoire for disease resistance. In the current study, we made use of tetraploid wheat mapping populations derived from a cross between durum wheat (cv. Langdon) and wild emmer (accession G18-16) to identify and map a new powdery mildew resistance gene derived from wild emmer wheat. Initially, the two parental lines were screened with a collection of 42 isolates of Blumeria graminis f. sp. tritici (Bgt) from Israel and 5 isolates from Switzerland. While G18-16 was resistant to 34 isolates, Langdon was resistant only to 5 isolates and susceptible to 42 isolates. Isolate Bgt#15 was selected to differentiate between the disease reactions of the two genotypes. Segregation ratio of F(2-3) and recombinant inbreed line (F(7)) populations to inoculation with isolate Bgt#15 indicated the role of a single dominant gene in conferring resistance to Bgt#15. This gene, temporarily designated PmG16, was located on the distal region of chromosome arm 7AL. Genetic map of PmG16 region was assembled with 32 simple sequence repeat (SSR), sequence tag site (STS), Diversity array technology (DArT) and cleaved amplified polymorphic sequence (CAPS) markers and assigned to the 7AL physical bin map (7AL-16). Using four DNA markers we established colinearity between the genomic region spanning the PmG16 locus within the distal region of chromosome arm 7AL and the genomic regions on rice chromosome 6 and Brachypodium Bd1. A comparative analysis was carried out between PmG16 and other known Pm genes located on chromosome arm 7AL. The identified PmG16 may facilitate the use of wild alleles for improvement of powdery mildew resistance in elite wheat cultivars via marker-assisted selection.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00122-010-1326-5DOI Listing
August 2010