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

Virus Diseases of Peanut

Breeding for resistance.

Laboratory protocols: CIMMYT applied molecular genetics laboratory

Life, Liberty and the Defense of Dignity: The Challenge for Bioethics

Grain soybean (Glycine max L.) is the primary source of vegetable protein for food and feed supplements, and accounts for much of the world’s oil supply. In most parts of Africa, soybean production potential is yet to be realised largely due to lack of improved varieties. Uganda’s soybean breeding programme has been actively involved in developing varieties to meet the needs of farmers in different parts of the country. This study was, conducted to determine the adaptation of new advanced generation soybean lines to identify high yielding stable lines, the most ideal testing environment and to determine the presence of soybean production mega environments in the country. Twenty one advanced generation soybean lines and three standard check varieties were evaluated in five sites and three consecutive rainy seasons. Results of AMMI analysis indicated the presence of a scale genotype-by-environment interaction for soybean grain yield. Through AMMI estimates and GGE visual assessment, BSPS48A was the highest yielding genotype in the most discriminating and stable environment, Nakabango. BSPS48A was, therefore, recommended for release subject to evaluation for commercial value. From the environmental focusing plot, the five multi-locations tested were grouped into two putative mega environments for soybean production.

/pdf/genotype-by-environment-interaction-of-advanced-generation-25kiw7krcb.pdf

Genotype by environment interaction of advanced generation soybean lines for grain yield in uganda

The threat posed by soybean rust (Phakopsora pachyrhizi) on soybean production is worsened by resistance breakdown associated with single gene resistance present in most cultivars. Few studies have however been undertaken to use mapped simple sequence markers for gene pyramiding to enhance rust resistance. This study validated use of identified simple sequence repeat markers for gene pyramiding, and determined the most effective pairwise gene combination for three independent soybean rust resistance genes, Rpp2, Rpp3 and Rpp4. Markers Satt460 and AF162283 were polymorphic for the three resistance genes among the parents and were therefore used in selections made in the F2 and F3 families. In the F2 generation, soybean plants (homozygous dominant or heterozygous at both loci) with two gene combinations had relatively lower disease severity and sporulation than the parents, suggesting complementary epistatic gene action for resistance. Similarly, homozygous F3 families showed lower severity, lesion density and sporulation. Gene Rpp3 contributed positively to resistance with various genetic backgrounds for most parameters measured, compared to Rpp2 and Rpp4 resistance genes. Overall, the results suggest that marker gene pyramiding is feasible and can substantially increase resistance to soybean rust through reduced severity and reduced sporulating lesions.

https://www.academicjournals.org/article/article1380814117_Maphosa et al.pdf

Enhancing soybean rust resistance through Rpp2, Rpp3 and Rpp4 pair wise gene pyramiding

A major impediment to breeding for resistance to Asian soybean rust (Phakopsora pachyrhizi) is the lack of stable sources of resistance, due to high variability in the pathogen. The objectives of this study were to assess comparative virulence of five diverse field isolates from major soybean producing areas in Uganda, and identify lines with resistance to isolates of soybean rust in seedling and adult plants under screen house and field conditions respectively. When inoculated with the five field isolates, all twelve lines evaluated showed diverse and mixed reactions, suggesting each location differed in soybean rust races and/or virulence. Experimental sites growing many diverse soybean lines yearly had the greatest diversity of soybean rust. The effectiveness of specific resistance genes was restricted to certain locations and gene Rpp2 previously resistant was ineffective producing a susceptible tan reaction at the seedling stage. A positive correlation between mean lesion density at the seedling stage and adult plant severity indicated that using field isolates to screen for seedling resistance can be a useful breeding approach to extrapolate resistance in adult plants. Overall, these results emphasise the relevance of using field isolates from the target areas to evaluate lines for soybean rust resistance.

/pdf/assessment-of-comparative-virulence-and-resistance-in-10j4r2of3r.pdf

Assessment of Comparative Virulence and Resistance in Soybean Using Field Isolates of Soybean Rust

There is a growing realization in African countries for the need to enhance the production of xerophytic crops, including Watermelon, Citrullus lanatus L., in the face of climate change. The object...

Watermelon production in Africa: challenges and opportunities

Groundnuts (Arachis hypogaea L.) are produced and consumed in several African countries due to their nutritious and hardy nature. However, they are prone to infection by aflatoxin producing Aspergillus spp. which can occur in the field or in storage. Aflatoxins are mycotoxins that contaminate a range of economically important crops. They are of great importance due to their effect on yield and marketability of food products. Exposure to aflatoxin through food and feed products poses a health risk to both humans and animals. Due to climatic conditions that prevail in Africa such as drought, excessive rainfall and extreme temperatures resulting from climate change and variability, aflatoxins are a big challenge. This paper sought to review key issues of aflatoxins in groundnut and current research efforts in their management from a plant breeding perspective. Varietal resistance to aflatoxin contamination remains a priority issue to effectively lower groundnut infection in farmers’ fields. Resistance breeding using seed traits has significant G × E interaction which limits its response to selection and ultimately its use. Pre-breeding, development of biotechnology tools, knowledge of pathogen population diversity and understanding gene networks to aid selection have potential to enhance resistance breeding for aflatoxin management. These proposed interventions however require concerted and collaborative effort as they are promising in sustaining aflatoxin management.

M. Maphosa

Papers

Genotype by environment interaction of advanced generation soybean lines for grain yield in uganda

Enhancing soybean rust resistance through Rpp2, Rpp3 and Rpp4 pair wise gene pyramiding

Assessment of Comparative Virulence and Resistance in Soybean Using Field Isolates of Soybean Rust

Watermelon production in Africa: challenges and opportunities

Current state of knowledge on groundnut aflatoxins and their management from a plant breeding perspective: Lessons for Africa