Hussein Shimelis

By E. T. Gwata and H. Shimelis

Part of the book: Crop Production

By H. Shimelis and E.T. Gwata

Part of the book: Crop Production

By E. T. Gwata, H. Shimelis and P. M. Matova

Tropical legumes such as cowpea (Vigna unguiculata) and tepary bean (Phaseolus acutifolius) are important in traditional smallholder cropping systems, particularly in sub-Saharan Africa. Both legumes are adapted to harsh environments including extreme temperatures, drought and poor soil fertility. They provide affordable sources of protein for human consumption and are valuable for income generation. These crops contribute significantly to soil fertility improvement through biological nitrogen fixation. In many parts of Africa, the productivity of these legumes is generally low partly because farmers grow unimproved varieties that are often produced for subsistence purposes on poor soils in mixed cropping systems with limited production inputs. Therefore, this research was designed to evaluate the potential of two distinct mutation breeding approaches in creating useful genetic variation in the two legumes in order to improve the agronomic attributes of both crops. The variation was determined by measuring a range of agronomic traits at both the seedling and adult plant stages. The results showed significant genetic variation among cowpea mutants that were induced with various doses of gamma radiation as well as among tepary bean mutants that were induced with a chemical mutagenic agent, ethyl methanesulphonate (EMS). The optimum doses at LD50 for two cowpea genotypes (Nakare and Shindimba) were ≤200 Gy while the third genotype (Bira) tolerated a dose three-fold higher. In the EMS mutagenesis of tepary bean, the estimated LD50 was ≤2.4% EMS (v/v). In both approaches, percent seed germination decreased with increased dose and the coefficients of determination for the linear functions were high (>75%), suggesting that there were notable associations between the reduction in seed germination and the concentration of the mutagen. At the adult plant stage, tepary bean showed that the mutant generation significantly (P < 0.05) influenced positively the important agronomic traits such as shoot dry weight, number of pods per branch and seed size. Dose effects were also significant for seed size. The field trials conducted in Zimbabwe showed >10.0% increase in both seed size and grain yield potential of some mutant cowpea genotypes compared with the standard check. These findings provide reference doses for large-scale gamma irradiation of cowpea as well as chemical mutagenesis for tepary bean. In addition, the germplasm produced from these approaches has the potential for selection in a range of agro-ecological conditions across the region, thus creating alternative cropping systems for the smallholder growers.

Part of the book: Alternative Crops and Cropping Systems

By Beyene Amelework, Demissew Abakemal, Hussein Shimelis and Mark Laing

Sorghum and maize are major cereal crops worldwide and key food security crops in Sub-Saharan Africa. The difference in the mating systems, maize as predominantly a cross-fertilizer and sorghum as a self-fertilizer is reflected in differences in visible phenotypic and genotypic variations. The reproductive differences dictate the level of genetic variation present in the two crops. Conventionally, a heterotic group assignment is made based on phenotypic values estimated through combining ability and heterosis analyses. However, phenotypic evaluation methods have their limitation due to the influence of the environment and may not reflect the heterotic pattern of the lines accurately. Therefore, more effective and complementary methods have been proposed for heterotic grouping of candidate lines. Estimation of molecular-based genetic distance has proven to be a useful tool to describe existing heterotic groups, to identify new heterotic groups, and to assign inbreds into heterotic groups. Among the molecular markers, microsatellites markers have proved to be a powerful tool for analyzing genetic diversity and for classifying inbred lines into heterotic groups. Therefore, the aim of this chapter was to elucidate the use of microsatellite markers in genetic diversity analysis and heterotic grouping of sorghum and maize.

Part of the book: Microsatellite Markers

By Abera Wende, Hussein Shimelis and Eastonce T. Gwata

Maize (Zea mays L.) is an important staple food crop in sub-Saharan Africa (SSA). The productivity of the crop is limited partly by the leaf blight disease caused by Exserohilum turcicum. In breeding for resistance to leaf blight, the germplasm needs to be well-characterized in order to design efficient breeding programs. This study evaluated the (i) genetic variability among maize inbred lines and (ii) diversity of selected medium to late maturity tropical maize inbred lines for hybrid breeding. Plants of 50 maize inbred lines were artificially inoculated in the field during 2011 and 2012. Disease severity and incidence as well as grain yield were measured. A subset of 20 elite maize inbred lines was genotyped using 20 SSR markers. The germplasm showed significant differences in reaction to leaf blight and were classified as either resistant or intermediate or susceptible. Mean disease severity varied from 2.04 to 3.25. Seven inbred lines were identified as potential sources of resistance to leaf blight for the genetic improvement of maize. The genotyping detected 108 alleles and grouped the inbred lines into five clusters consistent with their pedigrees. The genetic grouping in the source population will be useful in the exploitation of tropical maize breeding programs.

Part of the book: Maize Germplasm