Chromosome translocations in wild populations of tetraploid emmer wheat in Israel and Turkey

Translocation frequencies (as compared to the standard chromosome arrangement typified by that in Chinese Spring) in 9 or more genotypes from each of 15 populations of Triticum dicoccoides in Israel were determined. Data also were obtained from 2 genotypes of the southernmost population (Jaba). A single population from Turkey was also investigated. There were 119 genotypes with translocations in the sample of 171 genotypes investigated (70%). The frequency of translocations in different populations varied from 0.27 to 1.00, and all populations had 1 or more genotypes with one or more translocations. Some populations such as Qazrin appeared to be homogeneous for translocations, but most populations were heterogeneous. A sample of 17 genotypes from 12 of the populations were crossed with the Langdon D-genome disomic substitutions to determine the identity of the chromosomes involved in the translocations. There were nine genotypes with translocations and with the exception of a 2A/2B translocation, none of them involved the same chromosomes. The B-genome chromosomes were involved in translocations more frequently than the A-genome chromosomes. Translocation frequencies (TF) of the various populations were correlated with environmental variables, primarily with water availability and humidity, and possibly also with soil type. In general, TF was higher in peripheral populations in the ecologically heterogeneous frontiers of species distribution than in the central populations located in the catchment area of the upper Jordan valley.     

Natural selection of allozyme polymorphisms: a microgeographic climatic differentiation in wild emmer wheat (Triticum dicoccoides)

Summary Allozymic variation in proteins encoded by 48 loci was analyzed electrophoretically in 1984 and 1985 in 137 individual plants of wild emmer wheat, Triticum dicoccoides, from a microsite in Yehudiyya, northeast of the Lake of Galilee, Israel. The test involved two climatic microniches in the open Tabor oak forest (1) sunny between trees and (2) shady under trees' canopies. Significant genetic differentiation at single-, two- and multilocus structures was found between neighboring climatic niches, which were only separated by a few meters. Our results suggest that allozyme polymorphisms in wild emmer wheat are partly adaptive, and differentiate primarily at the multilocus level by climatic factors presumably related to aridity stress.     

Adaptive variation of pelage color within and between species of the subterranean mole rat (Spalax ehrenbergi) in Israel

Summary Color notations of dorsal pelage were analyzed in 451 adult subterranean mole rats, comprising 19 populations and 4 chromosomal species (2n=52, 54, 58 and 60) of the Spalax ehrenbergi superspecies in Israel. In addition, the color notations of soil samples from the collection sites were measured. In an attempt to evaluate the degree of correlation between pelage color of mole rats and the local soil color, each color was compared both macro- and microgeographically. The macrogeographic comparisons were among populations of the 4 chromosomal species, and the microgeographic comparisons were among pairs of geographically neighboring subpopulations which occur under similar climatic conditions but differ in soil type and color. The results indicate that 1. no differences in pelage color notation exist between the sexes; 2. pelage of mole rats is generally characterized by an over-all grayish color, but its shades vary regionally and locally in accordance with varying soil color; 3. a positive correlation was found between pelage and local soil colors in the macrogeographic analysis and this correlation was verified in a microgeographic comparison; 4. specimens from populations of the northern chromosomal species (2n=52, 54) mainly inhabit terra rossa and basalt soils, respectively, with reddish brown tones, and they tend to have a more reddish shade, whereas animals from the central species (2n=58), which inhabits mainly dark soils including alluvial clays, terra rossa and brown rendzina and the souther species 2n=60, which occurs mainly in light soil types such as pale rendzina, sandy loams and loess, tend to have a more yellowish shade. The general appearance of specimens from 2n=58 was dark gray while that of 2n=60 specimens was light gray; 5. mole rats living in xeric environments (particularly 2n=60, but also 2n=54) are lighter than those which live in mesic environments (2n=52, 58). The results support the conclusion that pelage color of strictly subterranean mole rats is subject to selection pressures of overground predation of disharmonious types with their background soil color. The possibility that the pelage color variation and patterns also contributes to better thermoregulation while mole rats are above ground is discussed.     

Ribosomal DNA non-transcribed spacer polymorphism in subterranean mole rats: genetic differentiation,environmental correlates and phylogenetic relationships

Summary An analysis is presented of genetic differentiation in the non-transcribed spacers of ribosomal DNA (NTS rDNA). Diversity, environmental correlates and the phylogenetic relationships are examined within and between species of the actively speciating subterranean mole rat, superspeciesSpalax ehrenbergi (2n=52, 54, 58, 60) in Israel. This analysis is based on a previous study of the geographic distribution of restriction fragment length polymorphisms of NTS rDNA. Here we present results indicating that NTS rDNA diversity exists mostly (66%) within populations, while 20% is between populations within species, and 14% between species. Multivariate discriminant analysis succeeded in separating 10 of the 13 populations (77%) into their correct chromosomal species, on the basis of the combination of three NTS rDNA repetypes. The phylogenetic relationships suggest that the complex involves two pairs of closely related species (2n=52–54 and 2n=58–60). NTS rDNA diversity, as well as the decrease southward in frequency of repetype C, are correlated with climatic factors of humidity and temperature. These data are discussed in terms of the evolutionary forces of migration and selection which may cause NTS rDNA differentiation. Climatic selection appears to be the major differentiating factor of NTS rDNA.     

Genetic diversity and environmental associations of wild barley,Hordeum spontaneum (Poaceae), in Iran

Genetic diversity and structure of populations of the wild progenitor of barleyHordeum spontaneum in Iran was studied by electrophoretically discernible allozymic variation in proteins encoded by 30 gene loci in 509 individuals representing 13 populations of wild barley. The results indicate that: a)Hordeum spontaneum in Iran is extremely rich genetically but, because of predominant self-pollination, the variation is carried primarily by different homozygotes in the population. Thus, genetic indices of polymorphismP-1% = 0.375, range = 0.267–0.500, and of genetic diversity,He = 0.134, range = 0.069–0.198, are very high. b) Genetic differentiation of populations includes clinal, regional and local patterns, sometimes displaying sharp geographic differentiation over short distances. The average relative differentiation among populations isGst = 0.28, range = 0.02–0.61. c) A substantial portion of the patterns of allozyme variation in the wild gene pool is significanctly correlated with the environment and is predictable ecologically, chiefly by combinations of temperature and humidity variables. d) The natural populations studied, on the average, are more variable than two composite crosses, and more variable than indigenous land races of cultivated barely,Hordeum vulgare, in Iran. — The spatial patterns and environmental correlates and predictors of genetic variation ofH. spontaneum in Iran indicate that genetic variation in wild barley populations is not only rich but also at least partly adaptive. Therefore, a much fuller exploitation of these genetic resources by breeding for disease resistance and economically important agronomic traits is warranted.     

Resistance of wild wheat to stripe rust: Predictive method by ecology and allozyme genotypes

From 114 accessions of wild emmer wheat from 11 sites in Israel, known for their allozymic variation (Nevo & al. 1982), individual genotypes were tested for resistance to one isolate of stripe rust both in the seedling stage in a growth chamber and in the adult plant stage in the field. The results indicate that resistance to stripe rust in seedlings and adults are significantly correlated (r_s = 0.40, p < 0.001). Genetic polymorphisms of resistance to stripe rust vary geographically and are predictable by climatic, as well as allozymic markers. Three variable combinations of rainfall, evaporation, and temperature explain significantly 0.40–0.53 of the spatial variance in disease resistance to stripe rust, suggesting the operation of natural selection. Several allozyme genotypes are significantly associated with disease resistance. We conclude that natural populations of wild emmer wheat in Israel contain large amounts of disease resistance genes. These populations could be effectively screened and then utilized by the phytopathologist for identifying resistant genotypes and producing new resistant cultivars.Patterns of Resistance of Wild Wheat to Pathogens in Israel II.     

Microsatellite diversity correlated with ecological-edaphic and genetic factors in three microsites of wild emmer wheat in North Israel

This study was conducted to test the effects of internal (genetic) and external factors on allelic diversity at 27 dinucleotide microsatellite (simple sequence repeat [SSR]) loci in three Israeli natural populations of Triticum dicoccoides from Ammiad, Tabigha, and Yehudiyya, north of the Sea of Galilee. The results demonstrated that SSR diversity is correlated with the interaction of ecological and genetic factors. Genetic factors, including genome (A vs. B), chromosome, motif, and locus, affected average repeat number (ARN), variance in repeat number (sigma), and number of alleles (NA) of SSRs, but the significance of some factors varied among populations. Genome effect on SSR variation may result from different motif types, particularly compound (or imperfect) versus perfect motifs, which may be related to different evolutionary histories of genomes A and B. Ecological factors significantly affected SSR variation. Soil-unique and soil-specific alleles were found in two edaphic groups dwelling on terra rossa and basalt soils across macro- and microgeographical scales. The largest contributions of genetic and ecological effects were found for diversity of ARN and NA, respectively. Multiple regression indicated that replication slippage and unequal crossing over could be important mutational mechanisms, but their significance varied among motifs. Edaphic stresses may affect the probability of replication errors and recombination intermediates and thus control diversity level and divergence of SSRs. The results may indicate that SSR diversity is adaptive, channeled by natural selection and influenced by both internal and external factors and their interactions.     

Natural selection causing microsatellite divergence in wild emmer wheat at the ecologically variable microsite at Ammiad, Israel

Genetic diversity at 28 microsatellite loci was studied in a natural population of Triticum dicoccoides at the Ammiad microsite, north of the Sea of Galilee, Israel. This microsite was subdivided into four major habitats, North, Valley, Ridge and Karst, and further subdivided into nine subhabitats. The units thus defined showed strong and highly significant differentiation in ecological factors; in particular with respect to cover, proximity and height of rocks, and surface soil moisture after early rains. The results showed that allele distributions at microsatellite loci were nonrandom and associated with habitats. Significant genetic differentiation and variation in repeat number were found among subpopulations in the four major habitats and nine subhabitats. Habitat-specific and -unique alleles and linkage disequilibria were observed in the Karst subpopulation. The subpopulations dwelling in drier habitats and subhabitats showed higher genetic diversities at microsatellite loci. These results suggest that natural selection, presumably through aridity stress, acts upon microsatellite divergence predominantly on noncoding sequences, thereby contributing to differences in fitness. Received: 9 September 1999 / Accepted: 16 September 1999     

More injuries in left-footed individual lizards and Sphenodon

In lizards and Sphenodon , often the fourth toes of individuals with intact tails have more subdigital lamellae on the right than on the left side, and the opposite situation frequently occurs in individuals with injured tails. The difference between intact and injured individuals in morphological directional asymmetry was statistically significant ( P <0.05) in 11.4% among 193 species from various lizard families. Lizard families varied in extent and direction of association, but no phylogenetic constraints were detected within genera. Statistical significance was greater in samples from homogenous geographic origin than from heterogeneous ones. Among gekkonid species, the difference was stronger in those with cursorial (terrestrial) habits, than in those with scansorial (rupestral or arboreal) habits. In Scincidae, loss seems more often lethal in left-footed than in right-footed individuals. Statistically significant associations between morphological left-side dominance and tail injury exist also in three independent lineages with reduced limbs (Anguidae, Scincidae and Teidae). Hence such association is probably not a result of limb function. Rather, left-side dominance seems to be the symptom of an unknown, perhaps organism-wide, detrimental trait. Polymorphism in morphological dominance existed in all species, suggesting advantages and disadvantages in different situations to both phenotypes. We propose the hypothesis that an inversion of side dominance may occur in a single trait without systematic inversion of side dominance in all traits of the body. Inversion in a single trait causes incompatibility in multiple-trait functions. Such a mechanism, rather than cultural conventions, could increase accident proneness also in left-handed Homo sapiens , and could explain increased proneness to accident and warfare mortality in left-handed men, beyond the possible involvement of cultural factors.     

Herbicide response polymorphisms in wild emmer wheat: ecological and isozyme correlations

Summary We demonstrate that the scores and frequencies of chlortoluron (CT) and metoxuron (MX) resistance and susceptible phenotypes of wild emmer wheat, Triticum dicoccoides, are correlated with ecological factors and allozyme markers. Some isozyme markers located on chromosome 6B (e.g. Adh,Est-4 and Got), which also harbours the CT and MX resistance gene, provide good genetic markers for herbicide resistance breeding. Significant correlations between herbicide and photosynthetic characters suggest that the evolution of herbicide resistance polymorphisms may be related to the process of photosynthesis in nature and predated domestication of cultivated wheat.