Endemic and panglobal genetic groups, and divergence of host-associated forms in worldwide collections of the wheat leaf rust fungus Puccinia triticina as determined by genotyping by sequencing.

The wheat leaf rust fungus, Puccinia triticina, is found in the major wheat growing regions of the world and is a leading cause of yield loss in wheat. Populations of P. triticina are highly variable for virulence to resistance genes in wheat and adapt quickly to resistance genes in wheat cultivars. The objectives of this study were to determine the genetic relatedness of worldwide collections of P. triticina using restriction site associated genotyping by sequencing. A total of 558 isolates of P. triticina from wheat producing regions in North America, South America, Europe, the Middle East, Ethiopia, Russia, Pakistan, Central Asia, China, New Zealand, and South Africa were characterized at 6745 single nucleotide loci. Isolates were also tested for virulence to 20 near-isogenic lines that differ for leaf rust resistance genes. Populations that were geographically proximal were also more closely related for genotypes. In addition, groups of isolates within regions that varied for genotype were similar to groups from other regions, which indicated past and recent migration across regions. Isolates from tetraploid durum wheat in five different regions were highly related with distinct genotypes compared to isolates from hexaploid common wheat. Based on a molecular clock, isolates from durum wheat found only in Ethiopia were the first to diverge from a common ancestor form of P. triticina that is found on the wild wheat relative Aegilops speltoides, followed by the divergence of isolates found worldwide that are virulent to durum wheat, and then by isolates found on common wheat.

Multilocus Genotypes of the Wheat Leaf Rust Fungus Puccinia triticina in Worldwide Regions Indicate Past and Current Long-Distance Migration.

Many plant pathogenic fungi have a global distribution across diverse ecological zones and agricultural production systems. Puccinia triticina, the wheat leaf rust fungus, is a major pathogen in many wheat production areas of the world. The objective of this research was to determine the genetic relatedness of P. triticina in different worldwide regions. A total of 831 single-uredinial isolates collected from 11 regions were characterized for multilocus genotype at 23 simple sequence repeat loci and for virulence to 20 lines of wheat with single genes for leaf rust resistance. A total of 424 multilocus genotypes and 497 virulence phenotypes were found. All populations had high heterozygosity and significant correlation between virulence and molecular variation, which indicated clonal reproduction. The populations from North America and South America, Central Asia and Russia, and the Middle East and Europe were closely related for multilocus genotypes and many individual isolates from other continental regions were closely related. Twenty-seven multilocus genotypes were found in more than one continental region, and 13 of these had isolates with identical virulence phenotypes. The wide geographic distribution of identical and highly related multilocus genotypes of P. triticina indicated past and more recent migration events facilitated by the spread of clonally produced urediniospores.

Mutations in AIFM1 cause an X-linked childhood cerebellar ataxia partially responsive to riboflavin.

BACKGROUND: AIFM1 encodes a mitochondrial flavoprotein with a dual role (NADH oxidoreductase and regulator of apoptosis), which uses riboflavin as a cofactor. Mutations in the X-linked AIFM1 were reported in relation to two main phenotypes: a severe infantile mitochondrial encephalomyopathy and an early-onset axonal sensorimotor neuropathy with hearing loss. In this paper we report two unrelated males harboring AIFM1 mutations (one of which is novel) who display distinct phenotypes including progressive ataxia which partially improved with riboflavin treatment. METHODS: For both patients trio whole exome sequencing was performed. Validation and segregation were performed with Sanger sequencing. Following the diagnosis, patients were treated with up to 200 mg riboflavin/day for 12 months. Ataxia was assessed by the ICARS scale at baseline, and 6 and 12 months following treatment. RESULTS: Patient 1 presented at the age of 5 years with auditory neuropathy, followed by progressive ataxia, vermian atrophy and axonal neuropathy. Patient 2 presented at the age of 4.5 years with severe limb and palatal myoclonus, followed by ataxia, cerebellar atrophy, ophthalmoplegia, sensorineural hearing loss, hyporeflexia and cardiomyopathy. Two deleterious missense mutations were found in the AIFM1 gene: p. Met340Thr mutation located in the FAD dependent oxidoreductase domain and the novel p. Thr141Ile mutation located in a highly conserved DNA binding motif. Ataxia score, decreased by 39% in patient 1 and 20% in patient 2 following 12 months of treatment. CONCLUSION: AIFM1 mutations cause childhood cerebellar ataxia, which may be partially treatable in some patients with high dose riboflavin.

Mitochondrial epileptic encephalopathy, 3-methylglutaconic aciduria and variable complex V deficiency associated with TIMM50 mutations.

Mitochondrial encephalopathies are a heterogeneous group of disorders that, usually carry grave prognosis. Recently a homozygous mutation, Gly372Ser, in the TIMM50 gene, was reported in an abstract form, in three sibs who suffered from intractable epilepsy and developmental delay accompanied by 3-methylglutaconic aciduria. We now report on four patients from two unrelated families who presented with severe intellectual disability and seizure disorder, accompanied by slightly elevated lactate level, 3-methylglutaconic aciduria and variable deficiency of mitochondrial complex V. Using exome analysis we identified two homozygous missense mutations, Arg217Trp and Thr252Met, in the TIMM50 gene. The TIMM50 protein is a subunit of TIM23 complex, the mitochondrial import machinery. It serves as the major receptor in the intermembrane space, binding to proteins which cross the mitochondrial inner membrane on their way to the matrix. The mutations, which affected evolutionary conserved residues and segregated with the disease in the families, were neither present in large cohorts of control exome analyses nor in our ethnic specific exome cohort. Given the phenotypic similarity, we conclude that missense mutations in TIMM50 are likely manifesting by severe intellectual disability and epilepsy accompanied by 3-methylglutaconic aciduria and variable mitochondrial complex V deficiency. 3-methylglutaconic aciduria is emerging as an important biomarker for mitochondrial dysfunction, in particular for mitochondrial membrane defects.

Microcephaly, intractable seizures and developmental delay caused by biallelic variants in TBCD: further delineation of a new chaperone-mediated tubulinopathy.

Microtubule dynamics play a crucial role in neuronal development and function, and several neurodevelopmental disorders have been linked to mutations in genes encoding tubulins and functionally related proteins. Most recently, variants in the tubulin cofactor D (TBCD) gene, which encodes one of the five co-chaperones required for assembly and disassembly of α/ß-tubulin heterodimer, were reported to underlie a recessive neurodevelopmental/neurodegenerative disorder. We report on five patients from three unrelated families, who presented with microcephaly, intellectual disability, intractable seizures, optic nerve pallor/atrophy, and cortical atrophy with delayed myelination and thinned corpus callosum on brain imaging. Exome sequencing allowed the identification of biallelic variants in TBCD segregating with the disease in the three families. TBCD protein level was significantly reduced in cultured fibroblasts from one patient, supporting defective TBCD function as the event underlying the disorder. Such reduced expression was associated with accelerated microtubule re-polymerization. Morpholino-mediated TBCD knockdown in zebrafish recapitulated several key pathological features of the human disease, and TBCD overexpression in the same model confirmed previous studies documenting an obligate dependency on proper TBCD levels during development. Our findings confirm the link between inactivating TBCD variants and this newly described chaperone-associated tubulinopathy, and provide insights into the phenotype of this disorder.

Creatine transporter deficiency: Novel mutations and functional studies.

X-linked cerebral creatine deficiency (MIM 300036) is caused by deficiency of the creatine transporter encoded by the SLC6A8 gene. Here we report three patients with this condition from Israel. These unrelated patients were evaluated for global developmental delays and language apraxia. Borderline microcephaly was noted in one of them. Diagnosis was prompted by brain magnetic resonance imaging and spectroscopy which revealed normal white matter distribution, but absence of the creatine peak in all three patients. Biochemical testing indicated normal plasma levels of creatine and guanidinoacetate, but an increased urine creatine/creatinine ratio. The diagnosis was confirmed by demonstrating absent ([14])C-creatine transport in fibroblasts. Molecular studies indicated that the first patient is hemizygous for a single nucleotide change substituting a single amino acid (c.619 C > T, p.R207W). Expression studies in HeLa cells confirmed the causative role of the R207W substitution. The second patient had a three base pair deletion in the SLC6A8 gene (c.1222_1224delTTC, p.F408del) as well as a single base change (c.1254 + 1G > A) at a splicing site in the intron-exon junction of exon 8, the latter occurring de novo. The third patient, had a three base pair deletion (c.1006_1008delAAC, p.N336del) previously reported in other patients with creatine transporter deficiency. These three patients are the first reported cases of creatine transporter deficiency in Israel.

A New Rust Disease on Wild Coffee (Psychotria nervosa) Caused by Puccinia mysuruensis sp. nov.

Psychotria nervosa, commonly called "wild coffee" (Rubiaceae), is an important ethno-medicinal plant in India. In 2010, a new rust disease of P. nervosa was observed in three regions of Mysore District, Karnataka (India), with disease incidence ranging from 58 to 63%.Typical symptoms of the rust disease on wild coffee were prominently visible during the early monsoon season (May to June), with chlorotic spots on the adaxial and black pustules (telia) on the abaxial leaf surface. Telia produced abundant teliospores, which were bicelled, pedicillate, and measured 33 to 45 by 19 to 30 µm. The germination of teliospores produced a typical metabasidium bearing four basidiospores, each containing two haploid nuclei. Spore stages of the wild coffee rust pathogen were studied using artificially inoculated healthy wild coffee plants with germinated teliospores. Only telia were observed on the inoculated plants, indicating that this rust fungus has an abbreviated microcyclic life cycle that includes only teliospores and basidiospores. Phylogenetic analysis based on internal transcribed spacer and partial large subunit (LSU) sequence data showed that the wild coffee rust pathogen is related to Macruropyxis fraxini, Puccinia bartholomaei, P. choridis, and P. sparganioidis. The herbarium sample of P. psychotriae was examined and was shown to be different with respect to telium size and teliospore dimensions (24 to 32 by 13 to 18 µm). Therefore, the rust pathogen causing wild coffee rust is a new species, P. mysuruensis sp. nov.

SLC1A4 mutations cause a novel disorder of intellectual disability, progressive microcephaly, spasticity and thin corpus callosum.

Two unrelated patients, presenting with significant global developmental delay, severe progressive microcephaly, seizures, spasticity and thin corpus callosum (CC) underwent trio whole-exome sequencing. No candidate variant was found in any known genes related to the phenotype. However, crossing the data of the patients illustrated that they both manifested pathogenic variants in the SLC1A4 gene which codes the ASCT1 transporter of serine and other neutral amino acids. The Ashkenazi patient is homozygous for a deleterious missense c.766G>A, p.(E256K) mutation whereas the Ashkenazi-Iraqi patient is compound heterozygous for this mutation and a nonsense c.945delTT, p.(Leu315Hisfs*42) mutation. Structural prediction demonstrates truncation of significant portion of the protein by the nonsense mutation and speculates functional disruption by the missense mutation. Both mutations are extremely rare in general population databases, however, the missense mutation was found in heterozygous mode in 1:100 Jewish Ashkenazi controls suggesting a higher carrier rate among Ashkenazi Jews. We conclude that SLC1A4 is the disease causing gene of a novel neurologic disorder manifesting with significant intellectual disability, severe postnatal microcephaly, spasticity and thin CC. The role of SLC1A4 in the serine transport from astrocytes to neurons suggests a possible pathomechanism for this disease and implies a potential therapeutic approach.

The neuropsychological profile of patients with 3-methylglutaconic aciduria type III, Costeff syndrome.

Costeff syndrome is a rare genetic neuro-ophthalmological syndrome consisting of early-onset bilateral optic atrophy along with a progressive complex motor disorder with elevated levels of urinary 3-methylglutaconic acid and 3-methylglutaric acid. While borderline to mild cognitive deficits have been considered to be common in patients with this syndrome, a comprehensive cognitive assessment has never been performed. The aim of the current study was to explore the cognitive profile associated with Costeff syndrome. Sixteen adult patients diagnosed with Costeff syndrome were administered a neuropsychological test battery that was composed of standardized verbal tests adapted for the blind. General intelligence ranged from average to borderline, with a group mean consistent with intact general cognitive functioning (VIQmean = 85, z = -1) in the low-average range of the general population. The auditory immediate and delayed memory indexes were in the average range and were significantly higher than the general cognitive functioning, whereas the working memory index was significantly lower than the general cognitive functioning. Adult patients with Costeff syndrome have intact global cognition and learning abilities and strong auditory memory performance. © 2015 Wiley Periodicals, Inc.

Genetic differentiation of Puccinia triticina populations in the Middle East and genetic similarity with populations in Central Asia.

Leaf rust of wheat, caused by Puccinia triticina, is a common and widespread disease in the Middle East. The objective of this study was to determine whether genetically differentiated groups of P. triticina are present in the Middle East region and to compare the population from the Middle East with the previously characterized population from Central Asia to determine whether genetically similar groups of isolates are found in the two regions. In total, 118 isolates of P. triticina collected from common wheat and durum wheat in Egypt, Israel, Turkey, Ethiopia, and Kenya were tested for virulence on 20 lines of wheat with single genes for leaf rust resistance and for molecular genotypes with 23 simple-sequence repeat (SSR) markers. After removal of isolates with identical virulence and SSR genotype in each country, 103 isolates were retained for further analysis. Clustering of SSR genotypes based on two-dimensional principal coordinates and virulence to wheat differential lines grouped the isolates into four Middle East (ME) groups. The two largest ME groups had virulence phenotypes typical of isolates collected from common wheat and two smaller ME groups had virulence typical of isolates collected from durum wheat. All pairs of ME groups were significantly differentiated for SSR genotype based on R(ST) and F(ST) statistics, and for virulence phenotype based on Φ(PT). All ME groups had observed values of heterozygosity greater than expected and significant fixation indices that indicated the clonal reproduction of urediniospores in the overall population. Linkage disequilibria for SSR genotypes was high across the entire population. The overall values of R(ST) and F(ST) were lower when isolates were grouped by country of origin that indicated the likely migration of isolates within the region. Although the two ME groups with virulence typical of isolates from common wheat were not differentiated for SSR genotype from groups of isolates from Central Asia based on R(ST), there was no direct evidence for migration between the two regions because all ME isolates differed from the Central Asia isolates for SSR genotypes.

Glyceryl triacetate for Canavan disease: a low-dose trial in infants and evaluation of a higher dose for toxicity in the tremor rat model.

Canavan disease (CD) is a fatal dysmyelinating genetic disorder associated with aspartoacylase deficiency, resulting in decreased brain acetate levels and reduced myelin lipid synthesis in the developing brain. Here we tested tolerability of a potent acetate precursor, glyceryl triacetate (GTA), at low doses in two infants diagnosed with CD, aged 8 and 13 months. Much higher doses of GTA were evaluated for toxicity in the tremor rat model of CD. GTA was given orally to the infants for up to 4.5 and 6 months, starting at 25 mg/kg twice daily, doubling the dose weekly until a maximum of 250 mg/kg reached. Wild-type and tremor rat pups were given GTA orally twice daily, initially at a dose of 4.2 g/kg from postnatal days 7 through 14, and at 5.8 g/kg from day 15 through 23, and thereafter in food (7.5%) and water (5%). At the end of the trial (approximately 90 to 120 days) sera and tissues from rats were analysed for changes in blood chemistry and histopathology. GTA treatment caused no detectable toxicity and the patients showed no deterioration in clinical status. In the high-dose animal studies, no significant differences in the mean blood chemistry values occurred between treated and untreated groups, and no lesions indicating toxicity were detectable in any of the tissues examined. Lack of GTA toxicity in two CD patients in low-dose trials, as well as in high-dose animal studies, suggests that higher, effective dose studies in human CD patients are warranted.

Genome size in natural and synthetic autopolyploids and in a natural segmental allopolyploid of several Triticeae species.

Nuclear DNA amount (1C) was determined by flow cytometry in the autotetraploid cytotype of Hordeum bulbosum, in the cytologically diploidized autotetraploid cytotypes of Elymus elongatus, Hordeum murinum subsp. murinum and Hordeum murinum subsp. leporinum, in Hordeum marinum subsp. gussoneanum, in their progenitor diploid cytotypes, and in a newly synthesized autotetraploid line of E. elongatus. Several lines collected from different regions of the distribution area of every taxon, each represented by a number of plants, were analyzed in each taxon. The intracytotype variation in nuclear DNA amount of every diploid and autotetraploid cytotype was very small, indicating that no significant changes have occurred in DNA amount either after speciation or after autopolyploid formation. The autotetraploid cytotypes of H. bulbosum and the cytologically diploidized H. marinum subsp. gussoneanum had the expected additive amount of their diploid cytotypes. On the other hand, the cytologically diploidized autotetraploid cytotypes of E. elongatus and H. murinum subsp. murinum and H. murinum subsp. leporinum had considerably less nuclear DNA (10%-23%) than the expected additive value. Also, the newly synthesized autotetraploid line of E. elongatus showed similar reduction in DNA as its natural counterpart, indicating that the reduction in genome size occurred in the natural cytotype during autopolyploidization. It is suggested that the diploid-like meiotic behavior of these cytologically dipolidized autotetraploids is caused by the instantaneous elimination of a large number of DNA sequences, different sequences from different homologous pairs, leading to differentiation of the constituent genomes. The eliminated sequences are likely to include those that participate in homologous recognition and initiation of meiotic pairing. A gene system determining exclusive bivalent pairing by utilizing the differentiation between the two groups of homologues has been presumably superimposed on the DNA reduction process.

Genetics of resistance to wheat leaf rust, stem rust, and powdery mildew in Aegilops sharonensis.

Aegilops sharonensis (Sharon goatgrass) is a wild relative of wheat and a rich source of genetic diversity for disease resistance. The objectives of this study were to determine the genetic basis of leaf rust, stem rust, and powdery mildew resistance in A. sharonensis and also the allelic relationships between genes controlling resistance to each disease. Progeny from crosses between resistant and susceptible accessions were evaluated for their disease reaction at the seedling and/or adult plant stage to determine the number and action of genes conferring resistance. Two different genes conferring resistance to leaf rust races THBJ and BBBB were identified in accessions 1644 and 603. For stem rust, the same single gene was found to confer resistance to race TTTT in accessions 1644 and 2229. Resistance to stem rust race TPMK was conferred by two genes in accessions 1644 and 603. A contingency test revealed no association between genes conferring resistance to leaf rust race THBJ and stem rust race TTTT or between genes conferring resistance to stem rust race TTTT and powdery mildew isolate UM06-01, indicating that the respective resistance genes are not linked. Three accessions (1644, 2229, and 1193) were found to carry a single gene for resistance to powdery mildew. Allelism tests revealed that the resistance gene in accession 1644 is different from the respective single genes present in either 2229 or 1193. The simple inheritance of leaf rust, stem rust, and powdery mildew resistance in A. sharonensis should simplify the transfer of resistance to wheat in wide crosses.

Nuclear DNA amount and genome downsizing in natural and synthetic allopolyploids of the genera Aegilops and Triticum.

Recent molecular studies in the genera Aegilops and Triticum showed that allopolyploidization (interspecific or intergeneric hybridization followed by chromosome doubling) generated rapid elimination of low-copy or high-copy, non-coding and coding DNA sequences. The aims of this work were to determine the amount of nuclear DNA in allopolyploid species of the group and to see to what extent elimination of DNA sequences affected genome size. Nuclear DNA amount was determined by the flow cytometry method in 27 natural allopolyploid species (most of which were represented by several lines and each line by several plants) as well as 14 newly synthesized allopolyploids (each represented by several plants) and their parental plants. Very small intraspecific variation in DNA amount was found between lines of allopolyploid species collected from different habitats or between wild and domesticated forms of allopolyploid wheat. In contrast to the constancy in nuclear DNA amount at the intraspecific level, there are significant differences in genome size between the various allopolyploid species, at both the tetraploid and hexaploid levels. In most allopolyploids nuclear DNA amount was significantly less than the sum of DNA amounts of the parental species. Newly synthesized allopolyploids exhibited a similar decrease in nuclear DNA amount in the first generation, indicating that genome downsizing occurs during and (or) immediately after the formation of the allopolyploids and that there are no further changes in genome size during the life of the allopolyploids. Phylogenetic considerations of the origin of the B genome of allopolyploid wheat, based on nuclear DNA amount, are discussed.

A mutation analysis of the phenylalanine hydroxylase (PAH) gene in the Israeli population.

Hyperphenylalaninemia (HPA) is a group of diseases characterized by a persistent elevation of phenylalanine levels in tissues and biological fluids. The most frequent form is phenylalanine hydroxylase deficiency, causing phenylketonuria (PKU). Among 159 Israeli patients (Jews, Muslim and Christian Arabs and Druze) with HPA, in whom at least one of the mutations was characterized, a total of 43 different mutations were detected, including seven novel ones. PKU was very rare among Ashkenazi Jews and relatively frequent among Jews from Yemen, the Caucasian Mountains, Bukhara and Tunisia. The mutations responsible for the high frequency were: exon3del (Yemenite Jews), L48S (Tunisian Jews) and E178G, P281L and L48S (Jews from the Caucasian Mountains and Bukhara). Among the non-Jewish Israeli citizens, the disease was relatively frequent in the Negev and in the Nazareth vicinity, and in many localities a unique mutation was detected, often in a single family. While marked genetic heterogeneity was observed in the Arab and Jewish populations, only one mutation A300S, was frequent in all of the communities. Several of the other frequent mutations were shared by the non-Ashkenazi Jews and Arabs; none were mutual to Ashkenazi Jews and Arabs.

Audiometric and imaging characteristics of distal renal tubular acidosis and deafness.

OBJECTIVE: Primary distal renal tubular acidosis with sensorineural hearing loss is a rare autosomal recessive disease, usually caused by mutations in the ATP6V1B1 gene. The aim of this study was to characterise the phenotype of this disease, with emphasis on the auditory findings, in a cohort of Israeli children. STUDY DESIGN: Prospective study of five children, from three unrelated families, with distal renal tubular acidosis and bilateral sensorineural hearing loss, with mutations in the ATP6V1B1 gene. METHODS: The following were collected from patients' medical records: biochemical and renal data, age at distal renal tubular acidosis diagnosis, and age at hearing loss. Hearing loss progression as well as current hearing status were assessed, and high resolution computed tomography of the temporal bone was performed. All patients underwent genetic testing. RESULTS: Four patients were diagnosed with distal renal tubular acidosis before the age of six months and one at 24 months. All had the classical findings of low blood pH and inappropriately high urine pH. Hearing loss was diagnosed between the ages of three months and two years. The hearing loss was bilateral, asymmetrical and progressive, occasionally with a conductive component. Two children underwent cochlear implantation, at ages 10 and 15 years. High resolution computed tomography, performed in four patients between the ages of 2.5 and 15 years, showed bilaterally enlarged vestibular aqueducts. This was the only radiological abnormality in the inner ear in all cases. A different mutation in the ATP6V1B1 gene was found in each family. CONCLUSION: Several types of mutations in the ATP6V1B1 gene may cause distal renal tubular acidosis and sensorineural hearing loss. Patients display a typical progressive type of hearing loss and have enlarged vestibular aqueducts, with no other abnormalities being observed on imaging.

Genome size and genome evolution in diploid Triticeae species.

One of the intriguing issues concerning the dynamics of plant genomes is the occurrence of intraspecific variation in nuclear DNA amount. The aim of this work was to assess the ranges of intraspecific, interspecific, and intergeneric variation in nuclear DNA content of diploid species of the tribe Triticeae (Poaceae) and to examine the relation between life form or habitat and genome size. Altogether, 438 plants representing 272 lines that belong to 22 species were analyzed. Nuclear DNA content was estimated by flow cytometry. Very small intraspecific variation in DNA amount was found between lines of Triticeae diploid species collected from different habitats or between different morphs. In contrast to the constancy in nuclear DNA amount at the intraspecific level, there are significant differences in genome size between the various diploid species. Within the genus Aegilops, the 1C DNA amount ranged from 4.84 pg in A. caudata to 7.52 pg in A. sharonensis; among genera, the 1C DNA amount ranged from 4.18 pg in Heteranthelium piliferum to 9.45 pg in Secale montanum. No evidence was found for a smaller genome size in annual, self-pollinating species relative to perennial, cross-pollinating ones. Diploids that grow in the southern part of the group's distribution have larger genomes than those growing in other parts of the distribution. The contrast between the low variation at the intraspecific level and the high variation at the interspecific one suggests that changes in genome size originated in close temporal proximity to the speciation event, i.e., before, during, or immediately after it. The possible effects of sudden changes in genome size on speciation processes are discussed.

Spatio-temporal genetic variation in populations of wild emmer wheat, Triticum turgidum ssp. dicoccoides, as revealed by AFLP analysis.

Genetic structure of natural populations of wild crop relatives has been the subject of many studies. Yet, most of them focused on the assessment of spatial genetic diversity, while information on long-term variation, affected by yearly changes, has been considered only in few cases. The present study aimed therefore, to estimate the spatio-temporal genetic variation in populations of wild emmer wheat, the progenitor of domesticated wheat, and to assess the contribution of spatial versus temporal factors to the maintenance of genetic variation in a population. Single spikes were collected in the years 1988 and 2002 from plants that grew in the same sampling points, from six different habitats in the Ammiad conservation site, Eastern Galilee, Israel. Seeds were planted in a nursery and DNA was extracted from each plant and analyzed by the AFLP method. Fourteen primer combinations yielded 1,545 bands of which 50.0 and 48.8% were polymorphic in the years 1988 and 2002, respectively. Genetic diversity was much larger within populations than between populations and the temporal genetic diversity was considerably smaller than the spatial one. Nevertheless, population genetic structure may vary to some degree in different years, mainly due to fluctuations in population size because of yearly rainfall variations. This may lead to predominance of different genotypes in different years. Clustering the plants by their genetic distances grouped them according to their habitats, indicating the existence of genotype-environment affinities. The significance of the results in relation to factors affecting the maintenance of polymorphism in natural populations is discussed.