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

The expected move towards more sustainable crop-livestock systems implies wider cultivation of perennial forage legumes. Alfalfa (Medicago sativa subsp. sativa) is the main perennial legume in most temperate regions, especially where farm systems rely largely on forage conservation. White clover (Trifolium repens) and red clover (Trifolium pratense) are dominant in specific regions and farm systems. Although breeding progress for disease and insect resistance has been achieved, these crops have shown lower rates of genetic gain for yield than major grain crops, owing to lower breeding investment, longer selection cycles, impossibility to capitalize on harvest index, outbreeding mating systems associated with severe inbreeding depression, and high interaction of genotypes with cropping conditions and crop utilizations. Increasing yield, persistence, adaptation to stressful conditions (drought; salinity; grazing) and compatibility with companion grasses are major breeding targets. We expect genetic gain for...

Achievements and Challenges in Improving Temperate Perennial Forage Legumes

Legumes are well recognized for their nutritional and health benefits as well as for their impact in the sustainability of agricultural systems. The threatening scenario imposed by climate change highlights the need for concerted research approaches in order to develop crops that are able to cope with environmental stresses, while increasing yield and quality. During the last decade, some physiological components and molecular players underlying abiotic stress responses of a broad range of legume species have been elucidated. Plant physiology approaches provided general outlines of plant responses, identifying stress tolerance-related traits or elite cultivars. A thorough identification of candidate genes and quantitative trait loci (QTLs) associated with these traits followed. Model legumes like Medicago truncatula, Lotus japonicus, and more recently, Glycine max provided valuable translational approaches for dissecting legume responses to abiotic stresses. The challenge now focuses on the translation of...

/pdf/abiotic-stress-responses-in-legumes-strategies-used-to-cope-4nzel82vj1.pdf

Abiotic Stress Responses in Legumes: Strategies Used to Cope with Environmental Challenges

Flowers of the hop plant provide both bitterness and “hoppy” flavor to beer. Hops are, however, both a water and energy intensive crop and vary considerably in essential oil content, making it challenging to achieve a consistent hoppy taste in beer. Here, we report that brewer’s yeast can be engineered to biosynthesize aromatic monoterpene molecules that impart hoppy flavor to beer by incorporating recombinant DNA derived from yeast, mint, and basil. Whereas metabolic engineering of biosynthetic pathways is commonly enlisted to maximize product titers, tuning expression of pathway enzymes to affect target production levels of multiple commercially important metabolites without major collateral metabolic changes represents a unique challenge. By applying state-of-the-art engineering techniques and a framework to guide iterative improvement, strains are generated with target performance characteristics. Beers produced using these strains are perceived as hoppier than traditionally hopped beers by a sensory panel in a double-blind tasting.

/pdf/industrial-brewing-yeast-engineered-for-the-production-of-14jmirx7u6.pdf

Industrial brewing yeast engineered for the production of primary flavor determinants in hopped beer.

Systems analysis of two alfalfa varieties, Wisfal (Medicago sativa ssp falcata var Wisfal) and Chilean (M sativa ssp sativa var Chilean), with contrasting tolerance/sensitivity to drought revealed common and divergent responses to drought stress At a qualitative level, molecular, biochemical, and physiological responses to drought stress were similar in the two varieties, indicating that they employ the same strategies to cope with drought However, quantitative differences in responses at all levels were revealed that may contribute to greater drought tolerance in Wisfal These included lower stomatal density and conductance in Wisfal; delayed leaf senescence compared with Chilean; greater root growth following a drought episode, and greater accumulation of osmolytes, including raffinose and galactinol, and flavonoid antioxidants in roots and/or shoots of Wisfal Genes encoding transcription factors and other regulatory proteins, and genes involved in the biosynthesis of osmolytes and (iso)flavonoids were differentially regulated between the two varieties and represent potential targets for improving drought tolerance in alfalfa in the future

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-313X.2011.04738.x

System responses to long‐term drought and re‐watering of two contrasting alfalfa varieties

Inadequate supplies of surface water limit forage production in the southern Great Plains and western United States. Alfalfa (Medicago sativa L.) production in this region may benefit from improvements in water-use efficiency (WUE), the amount of forage and root biomass produced per unit of water transpired. If benefits from improved WUE are to be realized, correlations between important agronomic traits and key physiological traits associated with WUE must be determined under water-limited conditions This study characterized genetic correlations among C isotope discrimination (Δ), canopy temperature, ash concentration, dry-matter yield, forage maturity, and leaf-to-stem ratio (LSR) in alfalfa grown under water-stressed field conditions. Heritabilities of the traits on a progeny mean basis were also determined. Thirty semidormant half-sib families were evaluated in seeded plots that were irrigated every 30 d during 2 yr near Las Cruces, NM. Carbon isotope discrimination was negatively correlated with canopy temperature and ash content. An increase in dry-matter yield was associated with higher Δ, lower canopy temperatures, low ash concentration, taller shoots, earlier maturity, and reduced LSR. Carbon isotope discrimination, ash concentration, and yield were moderately heritable (h 2 = 0.40-0.56) indicating that these traits could be altered through breeding and selection. The positive relationship between Δ and shoot yield suggests that germplasms should be evaluated for both Δ and yield when characterizing alfalfa for high WUE to minimize potential yield reductions that may result from selection based only on Δ. Moderate correlations between Δ and canopy temperature or ash content indicated that neither trait provided highly reliable estimates of Δ in water-stressed alfalfa.

Heritabilities of Water-Use Efficiency Traits and Correlations with Agronomic Traits in Water-Stressed Alfalfa

Considerable expertise is required to grow high-quality hops, and brewers and hop growers alike have a common goal of obtaining the highest quality hops possible. Changes in the chemical compositio...

/pdf/effect-of-harvest-maturity-on-the-chemical-composition-of-n5rayhkfeg.pdf

Effect of Harvest Maturity on the Chemical Composition of Cascade and Willamette Hops

Alfalfa (Medicago sativa L.) production under irrigated and rainfed conditions may benefit from improvements in water-use efficiency (WUE), the amount of forage and root biomass produced per unit of water transpired. If benefits from improved WUE are to be realized, correlations between important agronomic traits and key physiological traits associated with WUE must be determined. This study characterized variation for dry matter yield, forage maturity, leaf-to-stem ratio (LSR), carbon isotope discrimination (Δ), canopy temperature, ash content, and specific leaf mass (SLM) in alfalfa Associations between traits were also determined. Nine alfalfa germplasms representing eight of the nine historical genetic diversity groups, and a very fall-dormant (VFD) population, were established in seeded, irrigated plots for 2 yr near Las Cruces, NM. Significant variation (P ≤ 0.10) was detected for all traits and was greatest for Δ and maturity, intermediate for yield, canopy temperature, ash content, and LSR, and least for SLM. The African, Peruvian, and Indian germplasms exhibited a higher Δ than either the Turkistan, VFD, M. varia Martyn., or Ladak germplasms. Carbon isotope discrimination was positively correlated with forage yield (r = 0.64; P ≤ 0.10; n = 9) and forage maturity (r = 0.66; P ≤ 0.05; n = 9). No association was detected between Δ and either canopy temperature, ash content, SLM, or LSR. The results indicate that differences in stomatal conductance or photosynthetic capacity exist among the nine populations, and that germplasms with low Δ tended to have slower growth and development rates under irrigated conditions. Neither canopy temperature, ash content, nor SLM provided suitable alternate measurements of Δ among the nine alfalfa germplasms.

Variation for yield, water-use efficiency, and canopy morphology among nine alfalfa germplasms

Hop powdery mildew (Podosphaera mac- ularis (Wallr.) U. Braun & S. Takam.) is best controlled via the production of resistant varieties. Recent evidence supports selection against plant susceptibility genes to fungal pathogens as a more durable resistance mechanism than selection for resistance genes. The objective of this study was to identify molecular-based QTLs, their genetic effects and epistasis among QTLs associated with suscepti- bility to powdery mildew. Parents and offspring from the cross, 'Perle' 9 'USDA 19058M', were clonally replicated and inoculated in a greenhouse using a CRD experimental design in Corvallis, OR. DNA was extracted, purified and analyzed via three different marker systems. Analysis of the resulting markers was based upon the ''two-way pseudo- testcross'' procedure. QTL mapping using multiple interval mapping and Bayesian interval mapping analyses were performed using WinQTL Cartogra- pher 2.5_003. Comparison amongst mapping analy- ses identified three persistent QTLs on three linkage groups without significant epistatic effect upon expression. The persistent QTL on linkage group C7 had both additive and dominant effects control- ling phenotype expression. The presence or absence of the two AFLP markers bordering the QTL on C7 defined susceptibility in offspring. This is the first report in hop identifying molecular markers linked to QTLs associated with disease susceptibility.

https://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/43257/TownsendMShaunCropSoilSciencesQTLMappingPowdery.pdf;sequence=1

QTL mapping of powdery mildew susceptibility in hop (Humulus lupulus L.)

Hop (Humulus lupulus L.) is cultivated for the female fl owers, or “cones,” which traditionally have been used as a bittering and fl avoring agent in beer. Hop breeding historically relied on relatively simple selection techniques within established breeding lines. Supplementing current breeding material with new genetic sources would enhance a hop breeder’s ability to select for new traits. The objective of this research was to assess the genetic relationship of H. lupulus var. lupuloides and H. lupulus var. pubescens accessions with hop germplasm currently utilized by hop breeding programs. A total of 60 hop accessions representing both cultivated (n = 21) and native (n = 39) Humulus were evaluated using amplifi ed fragment length polymorphism (AFLP) molecular markers. The four primer combinations used generated 296 scorable fragments of which 176 (59.5%) were polymorphic. Principal components analysis and hierarchal cluster analysis showed the native American accessions clustering separately from the cultivated germplasm. Within each of the two main groups, two smaller subgroups were evident with H. lupulus var. lupuloides and H. lupulus var. pubescens segregated into unique clusters. This research provides the fi rst molecular genetic evidence of H. lupulus var. pubescens and H. lupulus var. lupuloides being two separate botanical varieties. Results from this research suggest incorporating the native American hop accessions studied in this experiment would enhance the genetic diversity within hop breeding programs.

https://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/43310/TownsendMShaunCropSoilSciencesAFLPDiscriminationNative.pdf;sequence=1

M. Shaun Townsend

Papers

Heritabilities of Water-Use Efficiency Traits and Correlations with Agronomic Traits in Water-Stressed Alfalfa

Effect of Harvest Maturity on the Chemical Composition of Cascade and Willamette Hops

Variation for yield, water-use efficiency, and canopy morphology among nine alfalfa germplasms

QTL mapping of powdery mildew susceptibility in hop (Humulus lupulus L.)

AFLP Discrimination of Native North American and Cultivated Hop