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

Genetics and analysis of quantitative traits

Climate change 2014 - Synthesis Report

Statistical Methods For Agricultural Workers

A reviewer for the Journal of the Royal Statistical Society of England comments \"This is the first book covering in one volume all important topics in genetical statistics.\" Written to provide basic probability ideas in terms of genetic situations, since the theory of genetics is a probability theory; to give a definitive treatment of applications of these ideas to genetic theory; and to describe statistical methods appropriate to the data models that are developed.

An Introduction to Genetic Statistics

Drought stress is one of the leading constraints to wheat (Triticum aestivum L.) production globally. Breeding for drought tolerance using novel genetic resources is an important mitigation strategy. This study aimed to determine the level of drought tolerance among diverse bread wheat genotypes using agronomic traits and proline analyses and to establish correlation of proline content and agronomic traits under drought-stress conditions in order to select promising wheat lines for breeding. Ninety-six diverse genotypes including 88 lines from the International Maize and Wheat Improvement Center (CIMMYT)’s heat and drought nurseries, and eight local checks were evaluated under greenhouse and field conditions during 2014/15 and 2015/16 making four testing environments. The following phenotypic traits were collected after stress imposed during the heading to anthesis period: the number of days to heading (DTH), days to maturity (DTM), productive tiller number (TN), plant height (PH), spike length (SL), spikelet per spike (SPS), kernels per spike (KPS), thousand kernel weight (TKW) and grain yield (GY) and proline content (PC). Analysis of variance, Pearson’s correlation coefficient, principal component and stress tolerance index were calculated. Genotypes with high yield performance under stressed and optimum conditions maintained high values for yield components. Proline content significantly increased under stress, but weakly correlated with agronomic traits under both optimal and water limited conditions. The positive correlation observed between grain yield and proline content under-drought stress conditions provides evidence that proline accumulation might ultimately be considered as a tool for effective selection of drought tolerant genotypes. The study selected 12 genotypes with high grain yields under drought stressed conditions and favorable adaptive traits useful for breeding.

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Screening of Bread Wheat Genotypes for Drought Tolerance Using Phenotypic and Proline Analyses.

Fusarium head blight of wheat: Pathogenesis and control strategies

Breeding wheat for drought tolerance: Progress and technologies

This study determined the population structure and genome-wide marker-trait association of agronomic traits of wheat for drought-tolerance breeding. Ninety-three diverse bread wheat genotypes were genotyped using the Diversity Arrays Technology sequencing (DArTseq) protocol. The number of days-to-heading (DTH), number of days-to-maturity (DTM), plant height (PHT), spike length (SPL), number of kernels per spike (KPS), thousand kernel weight (TKW) and grain yield (GYLD), assessed under drought-stressed and non-stressed conditions, were considered for the study. Population structure analysis and genome-wide association mapping were undertaken based on 16,383 silico DArTs loci with < 10% missing data. The population evaluated was grouped into nine distinct genetic structures. Inter-chromosomal linkage disequilibrium showed the existence of linkage decay as physical distance increased. A total of 62 significant (P < 0.001) marker-trait associations (MTAs) were detected explaining more than 20% of the phenotypic variation observed under both drought-stressed and non-stressed conditions. Significant (P < 0.001) MTA event(s) were observed for DTH, PHT, SPL, SPS, and KPS; under both stressed and non-stressed conditions, while additional significant (P < 0.05) associations were observed for TKW, DTM and GYLD under non-stressed condition. The MTAs reported in this population could be useful to initiate marker-assisted selection (MAS) and targeted trait introgression of wheat under drought-stressed and non-stressed conditions, and for fine mapping and cloning of the underlying genes and QTL.

/pdf/genome-wide-association-analysis-of-agronomic-traits-in-2hviq7hndj.pdf

Genome-wide association analysis of agronomic traits in wheat under drought-stressed and non-stressed conditions.

Potato (Solanum tuberosum L.) is a major food and cash crop in the Kenyan highlands, widely grown by small-scale farmers. Farmer practices and constraints in potato production differ from region to region. A survey was conducted in three major potato producing districts namely Bomet, Molo and Meru Central with the following objectives: 1) to document farmers’ practices, key potato production and marketing constraints, 2) to determine farmers’ potato cultivar and trait preferences and 3) to assess the prevalence and farmers’ management of bacterial wilt. The survey was carried out between November 2011 and March 2012. During the survey, a semi-structured questionnaire was administered to 253 individual farmers. The results show that the average household farm sizes are less than 2.4 hectares in all the districts. Majority of farmers allocate more than 25% of their farms to potatoes. Potato is produced both for food and cash by 90% of respondents in all districts. In Bomet district the red-skinned Dutch Robyjn is widely grown. In Molo district, the white- skinned Cangi is prominent while in Meru Central, the red-skinned Asante is predominantly grown by farmers. Cultivar preferences are mostly dictated by availability of markets, yield potential and taste. The major potato production constraints are diseases with bacterial wilt being the most prominent.

/pdf/potato-production-in-kenya-farming-systems-and-production-1lhtakqgv9.pdf

Hussein Shimelis

Papers

Screening of Bread Wheat Genotypes for Drought Tolerance Using Phenotypic and Proline Analyses.

Fusarium head blight of wheat: Pathogenesis and control strategies

Breeding wheat for drought tolerance: Progress and technologies

Genome-wide association analysis of agronomic traits in wheat under drought-stressed and non-stressed conditions.

Potato Production in Kenya: Farming Systems and Production Constraints