Publications by authors named "Zvi Peleg"

50 Publications

Deciphering the genetic basis of wheat seminal root anatomy uncovers ancestral axial conductance alleles.

Plant Cell Environ 2021 Jun 9;44(6):1921-1934. Epub 2021 Mar 9.

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

Root axial conductance, which describes the ability of water to move through the xylem, contributes to the rate of water uptake from the soil throughout the whole plant lifecycle. Under the rainfed wheat agro-system, grain-filling is typically occurring during declining water availability (i.e., terminal drought). Therefore, preserving soil water moisture during grain filling could serve as a key adaptive trait. We hypothesized that lower wheat root axial conductance can promote higher yields under terminal drought. A segregating population derived from a cross between durum wheat and its direct progenitor wild emmer wheat was used to underpin the genetic basis of seminal root architectural and functional traits. We detected 75 QTL associated with seminal roots morphological, anatomical and physiological traits, with several hotspots harbouring co-localized QTL. We further validated the axial conductance and central metaxylem QTL using wild introgression lines. Field-based characterization of genotypes with contrasting axial conductance suggested the contribution of low axial conductance as a mechanism for water conservation during grain filling and consequent increase in grain size and yield. Our findings underscore the potential of harnessing wild alleles to reshape the wheat root system architecture and associated hydraulic properties for greater adaptability under changing climate.
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http://dx.doi.org/10.1111/pce.14035DOI Listing
June 2021

Genomic Architecture of Phenotypic Plasticity in Response to Water Stress in Tetraploid Wheat.

Int J Mol Sci 2021 Feb 9;22(4). Epub 2021 Feb 9.

Institute of Evolution, University of Haifa, Haifa 3498838, Israel.

Phenotypic plasticity is one of the main mechanisms of adaptation to abiotic stresses via changes in critical developmental stages. Altering flowering phenology is a key evolutionary strategy of plant adaptation to abiotic stresses, to achieve the maximum possible reproduction. The current study is the first to apply the linear regression residuals as drought plasticity scores while considering the variation in flowering phenology and traits under non-stress conditions. We characterized the genomic architecture of 17 complex traits and their drought plasticity scores for quantitative trait loci (QTL) mapping, using a mapping population derived from a cross between durum wheat ( ssp. ) and wild emmer wheat ( ssp. ). We identified 79 QTLs affected observed traits and their plasticity scores, of which 33 reflected plasticity in response to water stress and exhibited epistatic interactions and/or pleiotropy between the observed and plasticity traits. () residing within an interval of a major drought-escape QTL was proposed as a candidate gene. The favorable alleles for most of the plasticity QTLs were contributed by wild emmer wheat, demonstrating its high potential for wheat improvement. Our study presents a new approach for the quantification of plant adaptation to various stresses and provides new insights into the genetic basis of wheat complex traits under water-deficit stress.
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http://dx.doi.org/10.3390/ijms22041723DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7915520PMC
February 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.
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http://dx.doi.org/10.1016/j.plantsci.2020.110785DOI Listing
February 2021

Genetic Architecture Underpinning Yield Components and Seed Mineral-Nutrients in Sesame.

Genes (Basel) 2020 10 18;11(10). Epub 2020 Oct 18.

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

Genetic dissection of yield components and seed mineral-nutrient is crucial for understanding plant physiological and biochemical processes and alleviate nutrient malnutrition. Sesame ( L.) is an orphan crop that harbors rich allelic repertoire for seed mineral-nutrients. Here, we harness this wide diversity to study the genetic architecture of yield components and seed mineral-nutrients using a core-collection of worldwide genotypes and segregating mapping population. We also tested the association between these traits and the effect of seed nutrients concentration on their bio-accessibility. Wide genetic diversity for yield components and seed mineral-nutrients was found among the core-collection. A high-density linkage map consisting of 19,309 markers was constructed and used for genetic mapping of 84 QTL associated with yield components and 50 QTL for seed minerals. To the best of our knowledge, this is the first report on mineral-nutrients QTL in sesame. Genomic regions with a cluster of overlapping QTL for several morphological and nutritional traits were identified and considered as genomic hotspots. Candidate gene analysis revealed potential functional associations between QTL and corresponding genes, which offers unique opportunities for synchronous improvement of mineral-nutrients. Our findings shed-light on the genetic architecture of yield components, seed mineral-nutrients and their inter- and intra- relationships, which may facilitate future breeding efforts to develop bio-fortified sesame cultivars.
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http://dx.doi.org/10.3390/genes11101221DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7603122PMC
October 2020

A Cytoplasmic Receptor-like Kinase Contributes to Salinity Tolerance.

Plants (Basel) 2020 Oct 17;9(10). Epub 2020 Oct 17.

Department of Plant Sciences, University of California, Davis, CA 95616, USA.

Receptor-like cytoplasmic kinases (RLCKs) are receptor kinases that lack extracellular ligand-binding domains and have emerged as a major class of signaling proteins that regulate plant cellular activities in response to biotic/abiotic stresses and endogenous extracellular signaling molecules. We have identified a rice RLCK (OsRLCK311) that was significantly higher in transgenic pSARK-IPT rice () that exhibited enhanced growth under saline conditions. Overexpression of OsRLCK311 full-length protein (RLCK311FL) and the C-terminus of OsRLCK311 (ΔN) in Arabidopsis confirmed its role in salinity tolerance, both in seedlings and mature plants. Protein interaction assays indicated that OsRLCK311 and ΔN interacted in-vivo with the plasma membrane AQP AtPIP2;1. The RLCK311-PIP2;1 binding led to alterations in the stomata response to ABA, which was characterized by more open stomata of transgenic plants. Moreover, OsRLCK311-ΔN effect in mediating enhanced plant growth under saline conditions was also observed in the perennial grass , confirming its role in both dicots and monocots species. Lastly, OsRLCK311 interacted with the rice OsPIP2;1. We suggest that the rice OsRLCK311 play a role in regulating the plant growth response under saline conditions via the regulation of the stomata response to stress. This role seems to be independent of the RLCK311 kinase activity, since the overexpression of the RLCK311 C-terminus (ΔN), which lacks the kinase full domain, has a similar phenotype to RLCK311FL.
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http://dx.doi.org/10.3390/plants9101383DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7650656PMC
October 2020

Tradeoffs between yield components promote crop stability in sesame.

Plant Sci 2020 Jun 30;295:110105. Epub 2019 Mar 30.

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

Sesame is an important oil-crop worldwide. Complex tradeoffs between various yield components significantly affect the outcome yield. Our aims were to characterize the effect of genotype, environment and management, and their interactions, on yield components. Wild-type line, bearing a bicarpellate-capsule and three capsules per leaf axil, and its derived mutant-line, featuring one tetracarpellate-capsule per leaf axil, were analyzed under two irrigation regimes and three sowing-stands. Dissection of flower meristems and capsules showed larger placenta size and final capsule diameter in the mutant-line. Allelic segregation of F population revealed that the number of carpels per capsule demonstrates monogenic inheritance, whereas the number of capsules per leaf axil is a polygenic trait. A significant effect of genotype, irrigation and stand was observed on most yield components. While wild-type had more capsules per plant, the mutant-line compensated by increased seed number per capsule and consequently accumulated the same number of seeds per plant. Under either high intra-row or inter-row density, the branches number was reduced; however, the outcome yield was compensated by number of plants per area. While some yield components showed phenotypic-plasticity (branching), other traits were genetically stable (number of capsules per leaf axil and number of carpels per capsule). Our result shed-light on tradeoffs between yield components and on their underlying mechanisms.
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http://dx.doi.org/10.1016/j.plantsci.2019.03.018DOI Listing
June 2020

Future challenges for global food security under climate change.

Authors:
Nir Sade Zvi Peleg

Plant Sci 2020 06 18;295:110467. Epub 2020 Mar 18.

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

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http://dx.doi.org/10.1016/j.plantsci.2020.110467DOI Listing
June 2020

Measuring the Hydraulic Conductivity of Grass Root Systems.

Curr Protoc Plant Biol 2020 06;5(2):e20110

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

Root-system hydraulic conductivity (RSHC) is an important physiological characteristic that describes the inherent ability of roots to conduct water across a water-potential gradient between the root and the stem xylem. RSHC is commonly used as an indicator of plant functioning and adaptability to a given environment. A simple, fast, and easy-to-use protocol is described for the quantification of RSHC at the seedling stage in two important monocot species grown in hydroponic solution: Setaria viridis, a C4 model plant, and wheat, a C3 crop plant. This protocol can also be easily modified for use with almost any grass species and environmental treatments, such as salinity or hormone treatments. © 2020 by John Wiley & Sons, Inc. Basic Protocol: Setaria hydrostatic root-system hydraulic conductivity Alternate Protocol: Measuring the root conductivity of young plants with soft stems.
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http://dx.doi.org/10.1002/cppb.20110DOI Listing
June 2020

Variation in phosphorus and sulfur content shapes the genetic architecture and phenotypic associations within the wheat grain ionome.

Plant J 2020 02 10;101(3):555-572. Epub 2019 Nov 10.

Institute of Evolution, University of Haifa, Haifa, 3498838, Israel.

Dissection of the genetic basis of wheat ionome is crucial for understanding the physiological and biochemical processes underlying mineral accumulation in seeds, as well as for efficient crop breeding. Most of the elements essential for plants are metals stored in seeds as chelate complexes with phytic acid or sulfur-containing compounds. We assume that the involvement of phosphorus and sulfur in metal chelation is the reason for strong phenotypic correlations within ionome. Adjustment of element concentrations for the effect of variation in phosphorus and sulfur seed content resulted in drastic change of phenotypic correlations between the elements. The genetic architecture of wheat grain ionome was characterized by quantitative trait loci (QTL) analysis using a cross between durum and wild emmer wheat. QTL analysis of the adjusted traits and two-trait analysis of the initial traits paired with either P or S considerably improved QTL detection power and accuracy, resulting in the identification of 105 QTLs and 617 QTL effects for 11 elements. Candidate gene search revealed some potential functional associations between QTLs and corresponding genes within their intervals. Thus, we have shown that accounting for variation in P and S is crucial for understanding of the physiological and genetic regulation of mineral composition of wheat grain ionome and can be implemented for other plants.
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http://dx.doi.org/10.1111/tpj.14554DOI Listing
February 2020

Genetic Screening for Mutants with Altered Seminal Root Numbers in Hexaploid Wheat Using a High-Throughput Root Phenotyping Platform.

G3 (Bethesda) 2019 09 4;9(9):2799-2809. Epub 2019 Sep 4.

John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK

Roots are the main channel for water and nutrient uptake in plants. Optimization of root architecture provides a viable strategy to improve nutrient and water uptake efficiency and maintain crop productivity under water-limiting and nutrient-poor conditions. We know little, however, about the genetic control of root development in wheat, a crop supplying 20% of global calorie and protein intake. To improve our understanding of the genetic control of seminal root development in wheat, we conducted a high-throughput screen for variation in seminal root number using an exome-sequenced mutant population derived from the hexaploid wheat cultivar Cadenza. The screen identified seven independent mutants with homozygous and stably altered seminal root number phenotypes. One mutant, Cadenza0900, displays a recessive extra seminal root number phenotype, while six mutants (Cadenza0062, Cadenza0369, Cadenza0393, Cadenza0465, Cadenza0818 and Cadenza1273) show lower seminal root number phenotypes most likely originating from defects in the formation and activation of seminal root primordia. Segregation analysis in F populations suggest that the phenotype of Cadenza0900 is controlled by multiple loci whereas the Cadenza0062 phenotype fits a 3:1 mutant:wild-type segregation ratio characteristic of dominant single gene action. This work highlights the potential to use the sequenced wheat mutant population as a forward genetic resource to uncover novel variation in agronomic traits, such as seminal root architecture.
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http://dx.doi.org/10.1534/g3.119.400537DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6723138PMC
September 2019

Phenotypic and metabolic plasticity shapes life-history strategies under combinations of abiotic stresses.

Plant Direct 2019 Jan 10;3(1):e00113. Epub 2019 Jan 10.

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

Plants developed various reversible and non-reversible acclimation mechanisms to cope with the multifaceted nature of abiotic-stress combinations. We hypothesized that in order to endure these stress combinations, plants elicit distinctive acclimation strategies through specific trade-offs between reproduction and defense. To investigate acclimation strategies to combinations of salinity, drought and heat, we applied a system biology approach, integrating physiological, metabolic, and transcriptional analyses. We analyzed the trade-offs among functional and performance traits, and their effects on plant fitness. A combination of drought and heat resulted in escape strategy, while under a combination of salinity and heat, plants exhibited an avoidance strategy. On the other hand, under combinations of salinity and drought, with or without heat stress, plant fitness (i.e., germination rate of subsequent generation) was severely impaired. These results indicate that under combined stresses, plants' life-history strategies were shaped by the limits of phenotypic and metabolic plasticity and the trade-offs between traits, thereby giving raise to distinct acclimations. Our findings provide a mechanistic understanding of plant acclimations to combinations of abiotic stresses and shed light on the different life-history strategies that can contribute to grass fitness and possibly to their dispersion under changing environments.
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http://dx.doi.org/10.1002/pld3.113DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6508786PMC
January 2019

GNI-A1 mediates trade-off between grain number and grain weight in tetraploid wheat.

Theor Appl Genet 2019 Aug 11;132(8):2353-2365. Epub 2019 May 11.

The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Hebrew University of Jerusalem, P.O. Box 12, 7610001, Rehovot, Israel.

Key Message: Wild emmer allele of GNI-A1 ease competition among developing grains through the suppression of floret fertility and increase grain weight in tetraploid wheat. Grain yield is a highly polygenic trait determined by the number of grains per unit area, as well as by grain weight. In wheat, grain number and grain weight are usually negatively correlated. Yet, the genetic basis underlying trade-off between the two is mostly unknown. Here, we fine-mapped a grain weight QTL using wild emmer introgressions in a durum wheat background and showed that grain weight is associated with the GNI-A1 gene, a regulator of floret fertility. In-depth characterization of grain number and grain weight indicated that suppression of distal florets by the wild emmer GNI-A1 allele increases weight of proximal grains in basal and central spikelets due to alteration in assimilate distribution. Re-sequencing of GNI-A1 in tetraploid wheat demonstrated the rich allelic repertoire of the wild emmer gene pool, including a rare allele which was present in two gene copies and contained a nonsynonymous mutation in the C-terminus of the protein. Using an F population generated from a cross between wild emmer accessions Zavitan, which carries the rare allele, and TTD140, we demonstrated that this unique polymorphism is associated with grain weight, independent of grain number. Moreover, we showed, for the first time, that GNI-A1 proteins are transcriptional activators and that selection targeted compromised activity of the protein. Our findings expand the knowledge of the genetic basis underlying trade-off between key yield components and may contribute to breeding efforts for enhanced grain yield.
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http://dx.doi.org/10.1007/s00122-019-03358-5DOI Listing
August 2019

Unleashing floret fertility in wheat through the mutation of a homeobox gene.

Proc Natl Acad Sci U S A 2019 03 21;116(11):5182-5187. Epub 2019 Feb 21.

Agrogenomics Research Center, National Institute of Agrobiological Sciences, 305-8602 Tsukuba, Japan;

Floret fertility is a key determinant of the number of grains per inflorescence in cereals. During the evolution of wheat ( sp.), floret fertility has increased, such that current bread wheat () cultivars set three to five grains per spikelet. However, little is known regarding the genetic basis of floret fertility. The locus () is shown here to be an important contributor to floret fertility. evolved in the Triticeae through gene duplication. The gene, which encodes a homeodomain leucine zipper class I (HD-Zip I) transcription factor, was expressed most abundantly in the most apical floret primordia and in parts of the rachilla, suggesting that it acts to inhibit rachilla growth and development. The level of expression has decreased over the course of wheat evolution under domestication, leading to the production of spikes bearing more fertile florets and setting more grains per spikelet. Genetic analysis has revealed that the reduced-function allele contributes to the increased number of fertile florets per spikelet. The RNAi-based knockdown of led to an increase in the number of both fertile florets and grains in hexaploid wheat. Mutants carrying an impaired allele out-yielded WT allele carriers under field conditions. The data show that gene duplication generated evolutionary novelty affecting floret fertility while mutations favoring increased grain production have been under selection during wheat evolution under domestication.
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http://dx.doi.org/10.1073/pnas.1815465116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6421441PMC
March 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.
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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.
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http://dx.doi.org/10.3389/fpls.2018.00075DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5829517PMC
February 2018

Activation of seminal root primordia during wheat domestication reveals underlying mechanisms of plant resilience.

Plant Cell Environ 2018 04 7;41(4):755-766. Epub 2018 Feb 7.

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

Seminal roots constitute the initial wheat root system and provide the main route for water absorption during early stages of development. Seminal root number (SRN) varies among species. However, the mechanisms through which SRN is controlled and in turn contribute to environmental adaptation are poorly understood. Here, we show that SRN increased upon wheat domestication from 3 to 5 due to the activation of 2 root primordia that are suppressed in wild wheat, a trait controlled by loci expressed in the germinating embryo. Suppression of root primordia did not limit water uptake, indicating that 3 seminal roots is adequate to maintain growth during seedling development. The persistence of roots at their primordial state promoted seedling recovery from water stress through reactivation of suppressed primordia upon rehydration. Our findings suggest that under well-watered conditions, SRN is not a limiting factor, and excessive number of roots may be costly and maladaptive. Following water stress, lack of substantial root system suppresses growth and rapid recovery of the root system is essential for seedling recovery. This study underscores SRN as key adaptive trait that was reshaped upon domestication. The maintenance of roots at their primordial state during seedling development may be regarded as seedling protective mechanism against water stress.
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http://dx.doi.org/10.1111/pce.13138DOI Listing
April 2018

Non-redundant functions of the dimeric ABA receptor BdPYL1 in the grass Brachypodium.

Plant J 2017 Dec 16;92(5):774-786. Epub 2017 Oct 16.

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

Abiotic stresses have severe detrimental effects on agricultural productivity worldwide. Abscisic acid (ABA) levels rise in response to abiotic stresses, and play a role in coordinating physiological responses. ABA elicits its effects by binding a family of soluble receptors, increasing affinity of the receptors to type 2C phosphatases (PP2Cs) leading to phosphatase inhibition. In the current study, we conducted a comprehensive analysis of the ABA signaling pathway in the cereal model grass Brachypodium distachyon. The Brachypodium genome encodes a family of 10 functionally conserved ABA receptors. The 10th in the series, BdPYL10, encodes a defective receptor and is likely a pseudogene. Combinatorial protein interaction assay further validated computational analysis, which grouped Brachypodium ABA receptors into three subfamilies, similarly to Arabidopsis classification. Brachypodium subfamily III receptors inhibited PP2C activity in vitro and complemented Arabidopsis quadruple (pyr1/pyl1/pyl2/pyl4) mutant. BdPYL1 T-DNA mutant exhibited clear ABA hyposensitivity phenotypes during seedling establishment and in mature plants. Single receptor predominance is in agreement with high transcriptional abundance of only a small Brachypodium ABA receptors subset, harboring the higher marginal significance of BdPYL1. Our findings suggest that unlike the highly redundant ABA core signaling components of Arabidopsis, Brachypodium encompasses a more compact and specialized ABA receptor apparatus. This organization may contribute to plant adaptations to ecological niches. These results lay the groundwork for targeting the prominent ABA receptors for stress perception in grasses, and reveal functional differences and commonalities between monocots and eudicots.
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http://dx.doi.org/10.1111/tpj.13714DOI Listing
December 2017

Different Mutations Endowing Resistance to Acetyl-CoA Carboxylase Inhibitors Results in Changes in Ecological Fitness of Populations.

Front Plant Sci 2017 22;8:1078. Epub 2017 Jun 22.

The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of JerusalemRehovot, Israel.

Various mutations altering the herbicide target site (TS), can lead to structural modifications that decrease binding efficiency and results in herbicide resistant weed. In most cases, such a mutation will be associated with ecological fitness penalty under herbicide free environmental conditions. Here we describe the effect of various mutations, endowing resistance to acetyl-CoA carboxylase (ACCase) inhibitors, on the ecological fitness penalty of populations. The TS resistant populations, MH (substitution of isoleucine 1781 to leucine) and NO (cysteine 2088 to arginine), were examined and compared to a sensitive population (AL). Grain weight (GW) characterization of individual plants from both MH and NO populations, showed that resistant individuals had significantly lower GW compared with sensitive ones. Under high temperatures, both TS resistant populations exhibited lower germination rate as compared with the sensitive (AL) population. Likewise, early vigor of plants from both TS resistant populations was significantly lower than the one measured in plants of the sensitive population. Under crop-weed intra-species competition, we found an opposite trend in the response of plants from different populations. Relatively to inter-population competition conditions, plants of MH population were less affected and presented higher reproduction abilities compared to plants from both AL and NO populations. On the basis of our results, a non-chemical approach can be taken to favor the sensitive individuals, eventually leading to a decline in resistant individuals in the population.
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http://dx.doi.org/10.3389/fpls.2017.01078DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5479926PMC
June 2017

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

Unraveling the Transcriptional Basis of Temperature-Dependent Pinoxaden Resistance in .

Front Plant Sci 2017 21;8:1064. Epub 2017 Jun 21.

The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of JerusalemRehovot, Israel.

Climate change endangers food security and our ability to feed the ever-increasing human population. Weeds are the most important biotic stress, reducing crop-plant productivity worldwide. Chemical control, the main approach for weed management, can be strongly affected by temperature. Previously, we have shown that temperature-dependent non-target site (NTS) resistance of is due to enhanced detoxification of acetyl-CoA carboxylase inhibitors. Here, we explored the transcriptional basis of this phenomenon. Plants were characterized for the transcriptional response to herbicide application, high-temperature and their combination, in an attempt to uncover the genetic basis of temperature-dependent pinoxaden resistance. Even though most of the variance among treatments was due to pinoxaden application (61%), plants were able to survive pinoxaden application only when grown under high-temperatures. Biological pathways and expression patterns of members of specific gene families, previously shown to be involved in NTS metabolic resistance to different herbicides, were examined. Cytochrome P450, glucosyl transferase and glutathione--transferase genes were found to be up-regulated in response to pinoxaden application under both control and high-temperature conditions. However, biological pathways related to oxidation and glucose conjugation were found to be significantly enriched only under the combination of pinoxaden application and high-temperature. Analysis of reactive oxygen species (ROS) was conducted at several time points after treatment using a probe detecting HO/peroxides. Comparison of ROS accumulation among treatments revealed a significant reduction in ROS quantities 24 h after pinoxaden application only under high-temperature conditions. These results may indicate significant activity of enzymatic ROS scavengers that can be correlated with the activation of herbicide-resistance mechanisms. This study shows that up-regulation of genes related to metabolic resistance is not sufficient to explain temperature-dependent pinoxaden resistance. We suggest that elevated activity of enzymatic processes at high-temperature may induce rapid and efficient pinoxaden metabolism leading to temperature-dependent herbicide resistance.
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http://dx.doi.org/10.3389/fpls.2017.01064DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5478685PMC
June 2017

Unique Physiological and Transcriptional Shifts under Combinations of Salinity, Drought, and Heat.

Plant Physiol 2017 May 17;174(1):421-434. Epub 2017 Mar 17.

The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Hebrew University of Jerusalem, Rehovot 7610001, Israel (L.S.-M., Z.P.); and

Climate-change-driven stresses such as extreme temperatures, water deficit, and ion imbalance are projected to exacerbate and jeopardize global food security. Under field conditions, these stresses usually occur simultaneously and cause damages that exceed single stresses. Here, we investigated the transcriptional patterns and morpho-physiological acclimations of to single salinity, drought, and heat stresses, as well as their double and triple stress combinations. Hierarchical clustering analysis of morpho-physiological acclimations showed that several traits exhibited a gradually aggravating effect as plants were exposed to combined stresses. On the other hand, other morphological traits were dominated by salinity, while some physiological traits were shaped by heat stress. Response patterns of differentially expressed genes, under single and combined stresses (i.e. common stress genes), were maintained only among 37% of the genes, indicating a limited expression consistency among partially overlapping stresses. A comparison between common stress genes and genes that were uniquely expressed only under combined stresses (i.e. combination unique genes) revealed a significant shift from increased intensity to antagonistic responses, respectively. The different transcriptional signatures imply an alteration in the mode of action under combined stresses and limited ability to predict plant responses as different stresses are combined. Coexpression analysis coupled with enrichment analysis revealed that each gene subset was enriched with different biological processes. Common stress genes were enriched with known stress response pathways, while combination unique-genes were enriched with unique processes and genes with unknown functions that hold the potential to improve stress tolerance and enhance cereal productivity under suboptimal field conditions.
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http://dx.doi.org/10.1104/pp.17.00030DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5411152PMC
May 2017

Effects of Environmental Conditions on the Fitness Penalty in Herbicide Resistant .

Front Plant Sci 2017 3;8:94. Epub 2017 Feb 3.

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

Herbicide-resistance mutations may impose a fitness penalty in herbicide-free environments. Moreover, the fitness penalty associated with herbicide resistance is not a stable parameter and can be influenced by ecological factors. Here, we used two accessions collected from the same planted forest, sensitive (S) and target-site resistance (TSR) to photosystem II (PSII) inhibitors, to study the effect of agro-ecological parameters on fitness penalty. Both accessions were collected in the same habitat, thus, we can assume that the genetic variance between them is relatively low. This allow us to focus on the effect of PSII TSR on plant fitness. S plants grains were significantly larger than those of the TSR plants and this was associated with a higher rate of germination. Under low radiation, the TSR plants showed a significant fitness penalty relative to S plants. S plants exhibiting dominance when both types of plants were grown together in a low-light environment. In contrast to previous documented studies, under high-light environment our TSR accession didn't show any significant difference in fitness compared to the S accession. Nitrogen deficiency had significant effect on the R compared to the S accession and was demonstrated in significant yield reduction. TSR plants also expressed a high fitness penalty, relative to the S plants, when grown in competition with wheat plants. Two evolutionary scenarios can be suggested to explain the coexistence of both TSR and S plants in the same habitat. The application of PSII inhibitors may have created selective pressure toward TSR dominancy; termination of herbicide application gave an ecological advantage to S plants, creating changes in the composition of the seed bank. Alternatively, the high radiation intensities found in the Mediterranean-like climate may reduce the fitness penalty associated with TSR. Our results may suggest that by integrating non-herbicidal approaches into weed-management programs, we can reduce the agricultural costs associated with herbicide resistance.
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http://dx.doi.org/10.3389/fpls.2017.00094DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5289963PMC
February 2017

Preface.

Plant Sci 2016 Oct;251

Department of Plant Sciences, University of California, Davis, CA 95616, USA.

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http://dx.doi.org/10.1016/j.plantsci.2016.08.008DOI Listing
October 2016

Climate change increases the risk of herbicide-resistant weeds due to enhanced detoxification.

Planta 2016 Dec 9;244(6):1217-1227. Epub 2016 Aug 9.

The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, P.O. Box 12, 7610001, Rehovot, Israel.

Main Conclusion: Global warming will increase the incidence of metabolism-based reduced herbicide efficacy on weeds and, therefore, the risk for evolution of non-target site herbicide resistance. Climate changes affect food security both directly and indirectly. Weeds are the major biotic factor limiting crop production worldwide, and herbicides are the most cost-effective way for weed management. Processes associated with climatic changes, such as elevated temperatures, can strongly affect weed control efficiency. Responses of several grass weed populations to herbicides that inhibit acetyl-CoA carboxylase (ACCase) were examined under different temperature regimes. We characterized the mechanism of temperature-dependent sensitivity and the kinetics of pinoxaden detoxification. The products of pinoxaden detoxification were quantified. Decreased sensitivity to ACCase inhibitors was observed under elevated temperatures. Pre-treatment with the cytochrome-P450 inhibitor malathion supports a non-target site metabolism-based mechanism of herbicide resistance. The first 48 h after herbicide application were crucial for pinoxaden detoxification. The levels of the inactive glucose-conjugated pinoxaden product (M5) were found significantly higher under high- than low-temperature regime. Under high temperature, a rapid elevation in the level of the intermediate metabolite (M4) was found only in pinoxaden-resistant plants. Our results highlight the quantitative nature of non-target-site resistance. To the best of our knowledge, this is the first experimental evidence for temperature-dependent herbicide sensitivity based on metabolic detoxification. These findings suggest an increased risk for the evolution of herbicide-resistant weeds under predicted climatic conditions.
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http://dx.doi.org/10.1007/s00425-016-2577-4DOI Listing
December 2016

Genetic Relationship in Cicer Sp. Expose Evidence for Geneflow between the Cultigen and Its Wild Progenitor.

PLoS One 2015 8;10(10):e0139789. Epub 2015 Oct 8.

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

There is a debate concerning mono- or poly-phyletic origins of the Near Eastern crops. In parallel, some authors claim that domestication was not possible within the natural range of the wild progenitors due to wild alleles flow into the nascent crops. Here we address both, the mono- or poly-phyletic origins and the domestications within or without the natural range of the progenitor, debates in order to understand the relationship between domesticated chickpea (Cicer arietinum L.) and its wild progenitor (C. reticulatum Ladizinsky) with special emphasis on its domestication centre in southeastern Turkey. A set of 103 chickpea cultivars and landraces from the major growing regions alongside wild accessions (C. reticulatum, C. echinospermum P.H Davis and C. bijugum K.H. Rech) sampled across the natural distribution range in eastern Turkey were genotyped with 194 SNPs markers. The genetic affinities between and within the studied taxa were assessed. The analysis suggests a mono-phyletic origin of the cultigen, with several wild accession as likely members of the wild stock of the cultigen. Clear separation between the wild and domesticated germplasm was apparent, with negligible level of admixture. A single C. reticulatum accession shows morphological and allelic signatures of admixture, a likely result of introgression. No evidence of geneflow from the wild into domesticated germplasm was found. The traditional farming systems of southeaster Turkey are characterized by occurrence of sympatric wild progenitor-domesticated forms of chickpea (and likewise cereals and other grain legumes). Therefore, both the authentic crop landraces and the wild populations native to the area are a unique genetic resource. Our results grant support to the notion of domestication within the natural distribution range of the wild progenitor, suggesting that the Neolithic domesticators were fully capable of selecting the desired phenotypes even when facing rare wild-domesticated introgression events.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0139789PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4597980PMC
June 2016

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

Genetic evidence for differential selection of grain and embryo weight during wheat evolution under domestication.

J Exp Bot 2015 Sep 27;66(19):5703-11. Epub 2015 May 27.

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

Wheat is one of the Neolithic founder crops domesticated ~10 500 years ago. Following the domestication episode, its evolution under domestication has resulted in various genetic modifications. Grain weight, embryo weight, and the interaction between those factors were examined among domesticated durum wheat and its direct progenitor, wild emmer wheat. Experimental data show that grain weight has increased over the course of wheat evolution without any parallel change in embryo weight, resulting in a significantly reduced (30%) embryo weight/grain weight ratio in domesticated wheat. The genetic factors associated with these modifications were further investigated using a population of recombinant inbred substitution lines that segregated for chromosome 2A. A cluster of loci affecting grain weight and shape was identified on the long arm of chromosome 2AL. Interestingly, a novel locus controlling embryo weight was mapped on chromosome 2AS, on which the wild emmer allele promotes heavier embryos and greater seedling vigour. To the best of our knowledge, this is the first report of a QTL for embryo weight in wheat. The results suggest a differential selection of grain and embryo weight during the evolution of domesticated wheat. It is argued that conscious selection by early farmers favouring larger grains and smaller embryos appears to have resulted in a significant change in endosperm weight/embryo weight ratio in the domesticated wheat. Exposing the genetic factors associated with endosperm and embryo size improves our understanding of the evolutionary dynamics of wheat under domestication and is likely to be useful for future wheat-breeding efforts.
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http://dx.doi.org/10.1093/jxb/erv249DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4566971PMC
September 2015

The rice transcription factor OsWRKY47 is a positive regulator of the response to water deficit stress.

Plant Mol Biol 2015 Jul 9;88(4-5):401-13. Epub 2015 May 9.

Instituto de Agrobiotecnología del Litoral (CONICET-UNL), Colectora ruta 168 km 0, Paraje El Pozo, 3000, Santa Fe, Argentina.

OsWRKY47 is a divergent rice transcription factor belonging to the group II of the WRKY family. A transcriptomic analysis of the drought response of transgenic rice plants expressing P SARK ::IPT, validated by qPCR, indicated that OsWRKY47 expression was induced under drought stress in P SARK ::IPT plants. A PCR-assisted site selection assay (SELEX) of recombinant OsWRKY47 protein showed that the preferred sequence bound in vitro is (G/T)TTGACT. Bioinformatics analyses identified a number of gene targets of OsWRKY47; among these two genes encode a Calmodulin binding protein and a Cys-rich secretory protein. Using Oswrk47 knockout mutants and transgenic rice overexpressing OsWRKY47 we show that the transcription of these putative targets were regulated by OsWRKY47. Phenotypic analysis carried out with transgenic rice plants showed that Oswrky47 mutants displayed higher sensitivity to drought and reduced yield, while plants overexpressing OsWRKY47 were more tolerant.
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http://dx.doi.org/10.1007/s11103-015-0329-7DOI Listing
July 2015

Identification of conserved drought-adaptive genes using a cross-species meta-analysis approach.

BMC Plant Biol 2015 May 3;15:111. Epub 2015 May 3.

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

Background: Drought is the major environmental stress threatening crop-plant productivity worldwide. Identification of new genes and metabolic pathways involved in plant adaptation to progressive drought stress at the reproductive stage is of great interest for agricultural research.

Results: We developed a novel Cross-Species meta-Analysis of progressive Drought stress at the reproductive stage (CSA:Drought) to identify key drought adaptive genes and mechanisms and to test their evolutionary conservation. Empirically defined filtering criteria were used to facilitate a robust integration of 17 deposited microarray experiments (148 arrays) of Arabidopsis, rice, wheat and barley. By prioritizing consistency over intensity, our approach was able to identify 225 differentially expressed genes shared across studies and taxa. Gene ontology enrichment and pathway analyses classified the shared genes into functional categories involved predominantly in metabolic processes (e.g. amino acid and carbohydrate metabolism), regulatory function (e.g. protein degradation and transcription) and response to stimulus. We further investigated drought related cis-acting elements in the shared gene promoters, and the evolutionary conservation of shared genes. The universal nature of the identified drought-adaptive genes was further validated in a fifth species, Brachypodium distachyon that was not included in the meta-analysis. qPCR analysis of 27, randomly selected, shared orthologs showed similar expression pattern as was found by the CSA:Drought.In accordance, morpho-physiological characterization of progressive drought stress, in B. distachyon, highlighted the key role of osmotic adjustment as evolutionary conserved drought-adaptive mechanism.

Conclusions: Our CSA:Drought strategy highlights major drought-adaptive genes and metabolic pathways that were only partially, if at all, reported in the original studies included in the meta-analysis. These genes include a group of unclassified genes that could be involved in novel drought adaptation mechanisms. The identified shared genes can provide a useful resource for subsequent research to better understand the mechanisms involved in drought adaptation across-species and can serve as a potential set of molecular biomarkers for progressive drought experiments.
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http://dx.doi.org/10.1186/s12870-015-0493-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4417316PMC
May 2015

Evolution of herbicide resistance mechanisms in grass weeds.

Plant Sci 2014 Dec 29;229:43-52. Epub 2014 Aug 29.

The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Hebrew University of Jerusalem, PO Box 12, Rehovot 7610001, Israel. Electronic address:

Herbicide resistant weeds are becoming increasingly common, threatening global food security. Here, we present BrIFAR: a new model system for the functional study of mechanisms of herbicide resistance in grass weeds. We have developed a large collection of Brachypodium accessions, the BrI collection, representing a wide range of habitats. Wide screening of the responses of the accessions to four major herbicide groups (PSII, ACCase, ALS/AHAS and EPSPS inhibitors) identified 28 herbicide-resistance candidate accessions. Target-site resistance to PSII inhibitors was found in accessions collected from habitats with a known history of herbicide applications. An amino acid substitution in the psbA gene (serine264 to glycine) conferred resistance and also significantly affected the flowering and shoot dry weight of the resistant accession, as compared to the sensitive accession. Non-target site resistance to ACCase inhibitors was found in accessions collected from habitats with a history of herbicide application and from a nature reserve. In-vitro enzyme activity tests and responses following pre-treatment with malathion (a cytochrome-P450 inhibitor) indicated sensitivity at the enzyme level, and give strong support to diclofop-methyl and pinoxaden enhanced detoxification as NTS resistance mechanism. BrIFAR can promote better understanding of the evolution of mechanisms of herbicide resistance and aid the implementation of integrative management approaches for sustainable agriculture.
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http://dx.doi.org/10.1016/j.plantsci.2014.08.013DOI Listing
December 2014