So far in this course we have dealt entirely with the evolution of characters that are controlled by simple Mendelian inheritance at a single locus. There are notes on the course website about gametic disequilibrium and how allele frequencies change at two loci simultaneously, but we didn’t discuss them. In every example we’ve considered we’ve imagined that we could understand something about evolution by examining the evolution of a single gene. That’s the domain of classical population genetics. For the next few weeks we’re going to be exploring a field that’s actually older than classical population genetics, although the approach we’ll be taking to it involves the use of population genetic machinery. If you know a little about the history of evolutionary biology, you may know that after the rediscovery of Mendel’s work in 1900 there was a heated debate between the “biometricians” (e.g., Galton and Pearson) and the “Mendelians” (e.g., de Vries, Correns, Bateson, and Morgan). Biometricians asserted that the really important variation in evolution didn’t follow Mendelian rules. Height, weight, skin color, and similar traits seemed to

Human biochemical genetics

Preface.- Contributors.- List of Abbreviations.- Section 1: Basic Principles: Introduction.-Sources of Heavy Metals and Metalloids in Soils.- Chemistry of Heavy Metals and Metalloids in Soils.- Methods for the Determination of Heavy Metals and Metalloids in Soils.- Effects of Heavy Metals and Metalloids on Soil Organisms.- Soil-Plant Relationships of Heavy Metals and Metalloids.- Heavy Metals and Metalloids as Micronutrients for Plants and Animals.-Critical Loads of Heavy Metals for Soils.- Section 2: Key Heavy Metals And Metalloids: Arsenic.- Cadmium.- Chromium and Nickel.- Cobalt and Manganese.- Copper.-Lead.- Mercury.- Selenium.- Zinc.- Section 3: Other Heavy Metals And Metalloids Of Potential Environmental Significance: Antimony.- Barium.- Gold.- Molybdenum.- Silver.- Thallium.- Tin.- Tungsten.- Uranium.- Vanadium.- Glossary of Specialized Terms.- Index.

Heavy metals in soils : trace metals and metalloids in soils and their bioavailability

A global perspective on cadmium pollution and toxicity in non-occupationally exposed population

Metals and micronutrients – food safety issues

The use of crop wild relatives (CWR) genes to improve crop performance is well established with important examples dating back more than 60 years. In this paper, we review available information on the presence of genes from CWR in released cultivars of 16 mandate crops of the CGIAR institutes, and some selected additional crops, focusing on the past 20 years—the period since a comprehensive review by Robert and Christine Prescott-Allen in 1986. It appears that there has been a steady increase in the rate of release of cultivars containing genes from CWR. While there continues to be a strong emphasis on using pest and disease resistance genes, a wider range of characteristics are being introduced than in the past. Those crops whose wild relatives have traditionally been used as sources of useful traits (e.g., wheat, tomato) continue to be most likely to include new genes from their wild relatives. CWR are continually gaining in importance and prevalence, but, we argue, their contributions to the development of new cultivars remain less than might have been expected given improved procedures for intercrossing species from different gene pools, advances in molecular methods for managing backcrossing programes, increased numbers of wild species accessions in gene banks, and the substantial literature on beneficial traits associated with wild relatives.

The use of wild relatives in crop improvement: a survey of developments over the last 20 years

Wild biotypes of cultivated sunflower ( Helianthus annuus L.) are weeds in corn ( Zea mays L.), soybean ( Glycine max L.), and other crops in North America, and are commonly controlled by applying acetohydroxyacid synthase (AHAS)-inhibiting herbicides. Biotypes resistant to two classes of AHAS-inhibiting herbicides-imidazolinones (IMIs) or sulfonylureas (SUs)-have been discovered in wild sunflower populations (ANN-PUR and ANN-KAN) treated with imazethapyr or chlorsulfuron, respectively. The goals of the present study were to isolate AHAS genes from sunflower, identify mutations in AHAS genes conferring herbicide resistance in ANN-PUR and ANN-KAN, and develop tools for marker-assisted selection (MAS) of herbicide resistance genes in sunflower. Three AHAS genes ( AHAS1, AHAS2, and AHAS3) were identified, cloned, and sequenced from herbicide-resistant (mutant) and -susceptible (wild type) genotypes. We identified 48 single-nucleotide polymorphisms (SNPs) in AHAS1, a single six-base pair insertion-deletion in AHAS2, and a single SNP in AHAS3. No DNA polymorphisms were found in AHAS2 among elite inbred lines. AHAS1 from imazethapyr-resistant inbreds harbored a C-to-T mutation in codon 205 ( Arabidopsis thaliana codon nomenclature), conferring resistance to IMI herbicides, whereas AHAS1 from chlorsulfuron-resistant inbreds harbored a C-to-T mutation in codon 197, conferring resistance to SU herbicides. SNP and single-strand conformational polymorphism markers for AHAS1, AHAS2, and AHAS3 were developed and genetically mapped. AHAS1, AHAS2, and AHAS3 mapped to linkage groups 2 ( AHAS3), 6 ( AHAS2), and 9 ( AHAS1). The C/T SNP in codon 205 of AHAS1 cosegregated with a partially dominant gene for resistance to IMI herbicides in two mutant x wild-type populations. The molecular breeding tools described herein create the basis for rapidly identifying new mutations in AHAS and performing MAS for herbicide resistance genes in sunflower.

/pdf/acetohydroxyacid-synthase-mutations-conferring-resistance-to-49uwpsuoj0.pdf

Acetohydroxyacid synthase mutations conferring resistance to imidazolinone or sulfonylurea herbicides in sunflower.

Cadmium (Cd) level in nonoilseed sunflower (Helianthus annuus L), flax (Linum usitatissimum L), and durum wheat (Triticum turgidum L var durum) grown on uncontaminated, alkaline soils has exceeded limits established in Northern Europe Separate field experiments were conducted to investigate variability of grain Cd levels among sunflower, durum wheat and flax germplasm, and to seek an efficient screening method for future breeding There were large variations in leaf Cd concentration among 200 sunflower lines These lines performed more consistently for Cd uptake at the R5 stage than at the V8 stage across 4 locations with markedly differing soils Cd concentration in V8 leaves was not related to Cd in grain The positive correlation between R5 leaf Cd and kernel Cd level was obtained from nonoilseed hybrid (Sigco 954) (R2; = 074**), and 200 lines (R2 = 044**) tested over 4 locations in 2 field trials, respectively This indicates that an efficient and low cost screening method can be developed for genotype selection, but plants must be grown to the R5 stage A preliminary evaluation of 30 durum wheat and 74 flax lines indicated large variations in grain Cd level of durum wheat and flax Grain Cd concentration ranged from 011 to 034 mg Cd kg-1 DW for durum wheat, and 014 to 137 mg Cd kg-1 DW for flax, respectively This variability indicates that breeding for low grain Cd in durum wheat and flax should be feasible

Screening for low grain cadmium phenotypes in sunflower, durum wheat and flax

Heterosis is significant for seed yield and is one of the driving forces behind the hybrid seed industry in cultivated sunflower (Helianthus annuus L). Heterotic groups in sunflower, if any other than the female and male inbred-line groups exist, have not been well studied or described. The primary aims of this study were to assess the utility and validity of a series of proposed heterotic groups and estimate correlations between genetic distance, heterosis, and hybrid performance for seed yield in sunflower. Fortytwo female by male heterotic group (A × R) and 81 female by female heterotic group (A × B) single-cross hybrids were grown in Corvallis, Ore., and Casselton, N.D., in 1996 and 1997. Heterosis was significant for seed yield and plant height but not for seed oil concentration and days to flowering. Genetic distances were significantly correlated with hybrid seed yield when estimated from AFLP fingerprints (GD) (r = 0.63 for A × R and 0.79 for A × B hybrids), but not from coancestries (GC) (r = -0.02 for A × R and 0.54 for A × B hybrids). GD (R2 = 0.4) was a poor predictor of hybrid seed yield. The proposed heterotic groups in sunflower seem to have utility, but do not seem to be as strongly differentiated as those in corn (Zea mays L.). The highest-yielding hybrids were from the BC× RB heterotic pattern; however, several BC× BC hybrids (within-group hybrids) were among the top-yielding hybrids. The outstanding performance of certain BC× BC hybrids casts some doubt on the validity of the BC group. Substantial genetic diversity seems to be present within and between heterotic groups in sunflower.

Genetic distance as a predictor of heterosis and hybrid performance within and between heterotic groups in sunflower.

An RFLP linkage map was constructed for cultivated sunflower Helianthus annuus L., based on 271 loci detected by 232 cDNA probes. Ninety-three F2 plants of a cross between inbred lines RHA 271 and HA 234 were used as the mapping population. These genetic markers plus a fertility restoration gene, Rf

 1, defined 20 linkage groups, covering 1164 cM of the sunflower genome. Of the 71 loci 202 had codominant genotypic segregation, with the rest showing dominant segregation. Thirty-two of the 232 probes gave multiple locus segregation. There were 39 clusters of tightly linked markers with 0 cM distance among loci. This map has an average marker-to-marker distance of 4.6 cM, with 11 markerless regions exceeding 20 cM.

Construction of an RFLP linkage map for cultivated sunflower

Production of nonoilseed sunflower (Helianthus annuus L.) on certain soil series yields kernels with cadmium (Cd) concentration excess of international market Cd limits. This study was conducted to determine if genetic variability exists among sunflower germplasm for low kernel Cd accumulation, and to select genotypes under varying soil conditions for breeding low kernel Cd cultivar(s). Two-hundred sunflower genotypes were evaluated at four different soil series in North Dakota and Minnesota. Large genetic variation in Cd content was found among genotypes. Kernel Cd concentrations showed continuous variation across the range of 0.31 to 1.34 mg/kg (average for four locations). Although Genotype × Location effect exists, genotypes were ranked similarly in Cd concentration at the four locations. Concentrations of Cd for the genotypes were highly correlated among locations, indicating genotypes performed consistently across the four environments. Results clearly show that genotypes for sunflower differ significantly in kernel Cd concentration, and it appears that this evaluation of 200 genotypes has identified sufficient low Cd germplasm for breeding low kernel Cd genotypes. Soil properties played an important role in Cd uptake and accumulation in sunflower. Data from the four soil series showed that fine textured soils from the Fargo and Grandin locations contained higher levels of diethylenetriaminepentaacetic acid (DTPA) extractable Cd and total Cd, and caused significantly higher sunflower kernel Cd across genotypes. Regressions for kernel Cd on soil measurements were all significant except for pH measures in deeper layer soil. The highly correlated relationship could be used to predict kernel Cd for some soil series which were not part of this study. North Dakota Agric. Exp. Stn. Journal no. 3622.

Jerry F. Miller

Papers

Acetohydroxyacid synthase mutations conferring resistance to imidazolinone or sulfonylurea herbicides in sunflower.

Screening for low grain cadmium phenotypes in sunflower, durum wheat and flax

Genetic distance as a predictor of heterosis and hybrid performance within and between heterotic groups in sunflower.

Construction of an RFLP linkage map for cultivated sunflower

Genotype Variation in Kernel Cadmium Concentration in Sunflower Germplasm under Varying Soil Conditions