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

Hop is a dioecious perennial with female plants grown commercially for brewing purposes. Parent selection in hop breeding on the basis of heterotic potential has not been reported in literature even though dominance has been reported in hops for several economically important traits. The objectives of this study were to determine if amplified fragment length polymorphism (AFLP)-based genetic distance among male and female accessions accurately reflect pedigree relationships and present information on potential heterotic crosses in hop. Nineteen cultivars were analyzed for genetic distance to 82 male accessions representing the assumed diversity of U.S. hops. Genetic distances (GD) between male/female pairs were estimated using AFLP (490 polymorphic bands). Distance estimates comparing males with females ranged from 0.169 to 0.62 with an overall average of 0.306. For each hop female, the 10 most genetically diverse and 10 most genetically similar males were identified and grouped. Coefficients of coancestry (COA) for each male/female pair within these groups were calculated using pedigree analysis. Values of COA for the genetically similar pairs (COA avg = 0.046) were significantly higher than the COA for the diverse pairs (COA avg = 0.013), suggesting that choosing male/female pairs on the basis of AFLP-based genetic distance may predict heterotic potential in crosses when GD >0.36.

/pdf/potential-heterotic-crosses-in-hops-as-estimated-by-aflp-fpdq84l66b.pdf

Potential Heterotic Crosses in Hops as Estimated by AFLP-Based Genetic Diversity and Coefficient of Coancestry

eamaker’ hop (Humulus lupulus L.) (Reg. No. CV-28, PI 558864) was developed by the USDA-ARS as a unique, nonbittering, high beta-acids hop and was released on 26 June 2006. The defi ning characteristics of Teamaker are its near-zero percent alpha acids levels—a distinctive condition in the Humulus species (Haunold et al., 1977)—good cone production, and relatively high levels of beta acids. Due to its low level of alpha acids, the primary bittering fl avor agent of hop, and high levels of beta acids, which are the primary antimicrobial active compounds in hop, the potential uses of this variety lie principally as a natural-product antimicrobial additive, replacing antibiotics in poultry feed (Cornelison et al., 2006); a bacteriostatic agent in sugar processing, replacing formaldehyde (Pollach et al., 1996); as an herbal tea; and as a “late-hopping” aroma hop addition to the brew kettle where bittering potential is of no consequence. Teamaker descended from the cross USDA 19105/USDA 19046M and, based on analysis of pedigree, has an inbreeding level F = 0.09375. The female, USDA 19105, was derived from the cross ‘Late Grape’/OP/3/‘Fuggle’//Fuggle/OP. Both Fuggle and Late Grape are thought to have arisen during the nineteenth century from clonal selections in Great Britain (Neve, 1991), although little is known about the parentage or origin of Late Grape. The male parent, USDA 19046M, was derived from ‘Late Cluster’/OP// Fuggle/OP. Genetic composition of Teamaker, based on pedigree analysis of known ancestors, is as follows: 31.25% Fuggle, 12.5% Late Grape, 12.5% Late Cluster (Neve, 1991), and the balance (43.75%) of unknown origin. Teamaker is a fairly vigorous cultivar with a cylindrical growth type, and its hop cones are distributed fairly uniformly along the length of the bine. This variety exhibits small- to medium-sized cones that mature moderately late with harvest dates similar to the industry standard ‘Nugget’ (Haunold et al., 1984). Harvest dates in Oregon ranged from 30 August to 23 September, with an

/pdf/registration-of-teamaker-hop-3yisr3vbtw.pdf

Registration of 'Teamaker' Hop

USDA 21087M (Reg. No. GP-36, PI 558607) male hop (Humulus lupulus L. var. lupulus) germplasm was released to the public on 6 Dec. 2011. This germplasm has been used by the USDA–ARS for hop cultivar development for several decades. Nonagency interest in this germplasm was expressed, and release of this material is considered beneficial for the US public. USDA 21087M was obtained from the former Yugoslavia by the USDA–ARS in 1974 as Selection 3/3. The defining characteristics of USDA 21087M are its high resistance to downy mildew in the US Pacific Northwest, potential resistance to non-v4/v6 strains of powdery mildew, and potential good storage ability in hop offspring. It is expected that hop breeders will use this germplasm as a parent for development of downy mildew– resistant hop cultivars. The release of USDA 21087M will give both public and private breeders new germplasm for cultivar and germplasm development.

https://acsess.onlinelibrary.wiley.com/doi/pdf/10.3198/jpr2017.09.0067crg

Registration of Downy Mildew–Resistant Male Hop Germplasm USDA 21087M

USDA 21267M (Reg. No. GP-37, PI 559093) male hop (Humulus lupulus L. var. lupulus) germplasm was released to the public 6 Dec. 2011. This germplasm has been used by the USDA–ARS for hop cultivar development for several decades. Nonagency interest in this germplasm was expressed, and release of this material is considered beneficial for the US public. USDA 21267M arose from a cross, made in 1973 involving the hop cultivar Comet and the USDA–ARS hop male germplasm 21110M. The defining characteristics of USDA 21267M are its high alpha acid levels observed in lupulin glands as well as good breeding value for yield, alpha and beta acid levels, and high xanthohumol levels. It is expected that hop breeders will use this germplasm as a parent for high-yielding, high-alpha hop breeding material. The release of USDA 21267M will give both public and private breeders new germplasm for varietal development.

https://acsess.onlinelibrary.wiley.com/doi/pdf/10.3198/jpr2017.09.0068crg

M. Shaun Townsend

Papers

Potential Heterotic Crosses in Hops as Estimated by AFLP-Based Genetic Diversity and Coefficient of Coancestry

Registration of 'Teamaker' Hop

Registration of Downy Mildew–Resistant Male Hop Germplasm USDA 21087M

Registration of High Alpha-Acid Male Hop Germplasm USDA 21267M