Papers by Cosmos Magorokosho
Journal of agricultural science, Jul 15, 2024
Low pH in soils is attributed as the main contributor to the low yields characteristic in maize p... more Low pH in soils is attributed as the main contributor to the low yields characteristic in maize production regions of Angola. Here, eight white-kernel acid soil tolerant donor lines (ASTDLs) sourced from CIMMYT-Colombia (testers) were crossed with eight white elite lines adapted to the mid-altitude climatic conditions from CIMMYT-Zimbabwe, in order to identify donor lines, which can be potential sources of acid tolerance genes in breeding programmes in Angola. The two groups of parents were crossed using a line by tester (L×T) mating design, yielding 47 crosses with sufficient seed, which were evaluated alongside eight acid tolerant commercial hybrids, during the 2014-16 cropping seasons at nine sites, representing acid and non-acid soils in Angola and Zimbabwe. Effects of general combining ability (GCA) due to lines and testers, as well as specific combining ability (SCA) on grain yield were significant (P < 0.05) under acid soils. From the CIMMYT-Zimbabwe breeding programme, inbred lines identified as ZW1, ZW4 and ZW5 together with the CIMMYT-Colombia ASTDLs (i.e.,
CW4 and CW8) seemed to be ideal parents for crosses that can do well under both the acid and non-acid soils. The best specific cross for acid soils was identified as ZW1 × CW8 (CH142512), whereas for non-acid soils, ZW3 ×CW4 (CH142500) was identified. Interestingly, the cross ZW1 × CW8 was also observed as stable under both acid and non-acid soil conditions. Overall, data showed potential of exotic acid tolerance donor lines for enhancing low-pH adaptation in sub-tropical maize populations.
Keywords: Acid soil, white maize, combining ability, genotype, acid soil tolerant donor lines (ASTDLs)
BMC Plant Biology, Aug 20, 2015
Background: Northern corn leaf blight (NCLB) caused by Exserohilum turcicum is a destructive dise... more Background: Northern corn leaf blight (NCLB) caused by Exserohilum turcicum is a destructive disease in maize. Using host resistance to minimize the detrimental effects of NCLB on maize productivity is the most cost-effective and appealing disease management strategy. However, this requires the identification and use of stable resistance genes that are effective across different environments. Results: We evaluated a diverse maize population comprised of 999 inbred lines across different environments for resistance to NCLB. To identify genomic regions associated with NCLB resistance in maize, a genome-wide association analysis was conducted using 56,110 single-nucleotide polymorphism markers. Single-marker and haplotype-based associations, as well as Anderson-Darling tests, identified alleles significantly associated with NCLB resistance. The single-marker and haplotype-based association mappings identified twelve and ten loci (genes), respectively, that were significantly associated with resistance to NCLB. Additionally, by dividing the population into three subgroups and performing Anderson-Darling tests, eighty one genes were detected, and twelve of them were related to plant defense. Identical defense genes were identified using the three analyses. Conclusion: An association panel including 999 diverse lines was evaluated for resistance to NCLB in multiple environments, and a large number of resistant lines were identified and can be used as reliable resistance resource in maize breeding program. Genome-wide association study reveals that NCLB resistance is a complex trait which is under the control of many minor genes with relatively low effects. Pyramiding these genes in the same background is likely to result in stable resistance to NCLB.
Characterization of maize germplasm grown in Eastern and Southern Africa: Results of the 2006 regional trials coordinated by CIMMYT
Inheritance of resistance to <i>Fusarium verticillioides</i> ear rot in maize inbred lines of southern, West and Central Africa origin
Crop Science, Jul 22, 2022
Maize (Zea mays L.) is an important crop in sub‐Sahara Africa for both human consumption and live... more Maize (Zea mays L.) is an important crop in sub‐Sahara Africa for both human consumption and livestock feed. Maize use is often limited by ear‐rotting fungi, some of which produce deleterious secondary metabolites. The aim of this study was to determine the inheritance of resistance to Fusarium verticillioides as an indirect way of selecting for resistance to secondary metabolites such as the mycotoxin fumonisin that is produced by this fungus, under artificial inoculation and natural infection. Twelve inbred lines from Seed Co that were used as the females, were mated to 12 tester lines from the International Institute of Tropical Agriculture (IITA) that were used as males, using the North Carolina Design II. The resulting 144 F1 hybrids and six check hybrids were evaluated in Zimbabwe. Artificial inoculation with F. verticillioides was done at Rattray Arnold Research Station in the first season. The general (GCA) and specific combining ability (SCA) effects for F. verticillioides incidence were variable across sites for the lines and the testers. Six southern African inbred lines had desirable GCA for F. verticillioides ear rot and can be used as resistance sources. Outstanding testers from IITA that had negative GCA for F. verticillioides ear rot and fumonisins were identified. Both additive and nonadditive effects were implicated in resistance to ear rot caused by F. verticillioides and potential lines were identified that can be used in regional breeding programs.
Replication Data for: Nonlinear heat effects on African maize as evidenced by historical yield trials
Maize variety options for Africa: Malawi
The effect of cadmium (Cd) accumulation on mineral composition in roots and shoots, growth develo... more The effect of cadmium (Cd) accumulation on mineral composition in roots and shoots, growth development, chlorophyll and water content of tomato (Solanum lycopersicon Mill 63/5F1) seedlings was tested under doses of 0 (control), 10, 50 and 100 µM. Cadmium accumulation was defined by elevated concentrations as 50 to 100 µM in root and shoot tissues. Element uptake by roots and shoot was negatively affected by raise in cadmium concentrations, especially in 100 µM Cd. Root and shoot elongation, root and shoot fresh and dry biomass, leaf area were negatively affected by increasing Cd concentrations. Tissue water content, growth tolerance index, chlorophyll a, chlorophyll b and total chlorophyll content were limited by cadmium toxicity. The addition of Cd in the growth medium also had significant deleterious effect on net photosynthetic rate (Pn) and intracellular CO 2 concentration (Ci), with Pn being reduced by 27.2 and 62.1% at 5 μmol/L and 100 µM Cd treatments compared to the control, respectively, while Ci increased correspondingly by 28.4 and 39.3%.
Phenotyping for abiotic stress tolerance in maize low nitrogen stress: a field manual
African Journal of Biotechnology
Maize is an important staple crop for humans and livestock feed in Zambia. A total of 473 maize g... more Maize is an important staple crop for humans and livestock feed in Zambia. A total of 473 maize germplasms were screened under maize lethal necrosis (MLN) artificial inoculation and disease pressure using an alpha lattice design to identify potential tolerant varieties as sources of resistance. The analysis of variance (ANOVA) based on the MLN score range of 1-9 showed that the levels of MLN resistance in the maize germplasms were very low, with almost all the hybrids widely grown in Zambia and germplasms drawn from the genebank found to be highly susceptible. However, the pro vitamin A varieties, GV662A and IICZ3085 showed a moderate level of resistance/tolerance, with disease scores of 4.7 and 5.3, respectively. There is need to enhance development of MLN tolerant maize cultivars by the national maize breeding programme and seed companies to avert the possible calamity posed by the threat of the effects of MLN. In addition, intensive awareness creation among various stakeholders in the maize value chain, systematic monitoring and surveillance of MLN, practicing integrated disease management approaches such as avoiding maize monoculture and continuous cultivations of susceptible maize throughout the year, and practicing maize crop rotation with compatible crops especially legumes that do not serve as hosts for maize chlorotic mottle virus (MCMV)/MLN are recommended.
Agronomy, Sep 16, 2022
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
BMC Plant Biology, 2019
Background: Maize yield potential is rarely maximized in sub-Saharan Africa (SSA) due to the deva... more Background: Maize yield potential is rarely maximized in sub-Saharan Africa (SSA) due to the devastating effects of drought stress and Striga hermonthica parasitism. This study was conducted to determine the gains in grain yield and associated changes in an early-maturing yellow bi-parental maize population (TZEI 17 x TZEI 11) F 3 following genomic selection (GS) for improved grain yield, Striga resistance and drought tolerance. Fifty S 1 lines were extracted from each of cycles C 0 , C 1 , C 2 and C 3 of the population and crossed to a tester TZEI 23 to generate 200 testcrosses. The testcrosses were evaluated under drought, artificial Striga-infested and optimal (free from Striga infestation and without limitation of water and nitrogen) environments in Nigeria, 2014-2017. Results: Gains in grain yield of 498 kg ha − 1 cycle − 1 (16.9% cycle − 1) and 522 kg ha − 1 cycle − 1 (12.6% cycle − 1) were obtained under Striga-infested and optimal environments, respectively. The yield gain under Striga-infested environments was associated with increased plant and ear heights as well as improvement in root lodging resistance, husk cover, ear aspect and Striga tolerance. Under optimal environments, yield gain was accompanied by increase in plant and ear heights along with improvement of husk cover and ear rot resistance. In contrast, genomic selection did not improve grain yield under drought but resulted in delayed flowering, poor pollen-silk synchrony during flowering and increased ear height. Genetic variances and heritabilities for most measured traits were not significant for the selection cycles under the research environments. Ear aspect was a major contributor to grain yield under all research environments and could serve as an indirect selection criterion for simultaneous improvement of grain yield under drought, Striga and optimal environments. Conclusion: This study demonstrated that genomic selection was effective for yield improvement in the bi-parental maize population under Striga-infested environments and resulted in concomitant yield gains under optimal environments. However, due to low genetic variability of most traits in the population, progress from further genomic selection could only be guaranteed if new sources of genes for Striga resistance and drought tolerance are introgressed into the population.
Climate and Development, 2017
Drought is a huge limiting factor in maize production, mainly in the rain-fed agriculture of sub-... more Drought is a huge limiting factor in maize production, mainly in the rain-fed agriculture of sub-Saharan Africa. In response to this threat, drought-tolerant (DT) maize varieties have been developed with an aim to ensure maize production under mild drought conditions. We conducted a study to assess the impact of smallholder farmers' adoption of DT maize varieties on total maize production. Data for the study came from a survey of 200 randomly sampled households in two districts of Chiredzi and Chipinge in southeastern Zimbabwe. The study found that 93% of the households were growing improved maize varieties and that 30% of the sampled households were growing DT maize varieties. Total maize yield was 436.5 kg/ha for a household that did not grow DT maize varieties and 680.5 kg/ha for households that grew DT maize varieties. We control for the endogeneity of the DT adoption variable, by using the control function approach to estimate total maize production in a Cobb-Douglas model. The results show that households that grew DT maize varieties had 617 kg/ha more maize than households that did not grow the DT maize varieties. Given that almost all farmers buy their seeds in the market, a change in varieties to DT maize seeds gives an extra income of US$240/ha or more than nine months of food at no additional cost. This has huge implications in curbing food insecurity and simultaneously saving huge amounts of resources at the household and national levels, which are used to buy extra food during the lean season.
Euphytica, 2015
Contamination of maize grain with mycotoxins including aflatoxin and fumonisin poses a threat to ... more Contamination of maize grain with mycotoxins including aflatoxin and fumonisin poses a threat to human health and livestock. The objectives of this study were to determine the current status of incidence of ear rot causing fungi, which are associated with mycotoxin contamination, in southern African maize hybrids, and to check whether or not mycotoxin resistance genes can be stacked in a single product. The 327 hybrids were evaluated under natural conditions in replicated trials over two seasons at Cedara Research Station, which is hot spot site for ear rot diseases. Concurrently, aflatoxin and fumonisin resistant tropical maize inbred lines were crossed with South African adapted inbred lines. The resultant 72 single crosses were evaluated for fumonisin contamination, while 44 three-way crosses and their progenies (146 S 2:3 families) were evaluated for both aflatoxin and fumonisin contamination under artificial inoculation. The
Characterization of local maize landraces from Zimbabwe, Zambia and Malawi
… Genetic Diversity to …, 2006
... Farmers' local varieties collected from marginal environments may possess some unique ph... more ... Farmers' local varieties collected from marginal environments may possess some unique physiological attributes that may not be present in germplasm not exposed to abiotic stress (Blum and Sullivan 1986). ... CIMMYT/UNDP, Mexico DF Blum, A. and CY Sullivan. 1986. ...
Scientific Reports
Fostering a culture of continuous improvement through regular monitoring of genetic trends in bre... more Fostering a culture of continuous improvement through regular monitoring of genetic trends in breeding pipelines is essential to improve efficiency and increase accountability. This is the first global study to estimate genetic trends across the International Maize and Wheat Improvement Center (CIMMYT) tropical maize breeding pipelines in eastern and southern Africa (ESA), South Asia, and Latin America over the past decade. Data from a total of 4152 advanced breeding trials and 34,813 entries, conducted at 1331 locations in 28 countries globally, were used for this study. Genetic trends for grain yield reached up to 138 kg ha−1 yr−1 in ESA, 118 kg ha−1 yr−1 South Asia and 143 kg ha−1 yr−1 in Latin America. Genetic trend was, in part, related to the extent of deployment of new breeding tools in each pipeline, strength of an extensive phenotyping network, and funding stability. Over the past decade, CIMMYT’s breeding pipelines have significantly evolved, incorporating new tools/techno...
Agronomy
Exotic germplasm (i.e., germplasm beyond the breeder’s target area) has traditionally been used t... more Exotic germplasm (i.e., germplasm beyond the breeder’s target area) has traditionally been used to broaden the genetic base of local (germplasm within the breeder’s target area) populations, but little has been done to assess gains that could be induced by this breeding practice in the sub-tropical regions of Africa. Here, eight maize (Zea mays L.) inbred lines developed from pedigree crosses of exotic and local (i.e., sub-tropically adapted lines; STALs) were inter-mated together with six elite STALs, in a partial diallel mating scheme, in order to depict yield gains that can be made when exotic genes are integrated within the sub-tropical maize germplasm pool. The crossing scheme yielded a total of 91 F1s which were evaluated together with nine commercial checks in multi-environmental trials (METs) at eight locations representing agro-ecologies in which maize is predominantly grown in Zimbabwe. Across site Analysis of Variance (ANOVA) showed differences in grain yield (GY) perform...
New techniques for breeding maize (Zea mays) varieties with fall armyworm resistance and market‐preferred traits for sub‐Saharan Africa
Plant Breeding
Deploying maize varieties with fall armyworm (Spodoptera frugiperda [J.E. Smith]; FAW) resistance... more Deploying maize varieties with fall armyworm (Spodoptera frugiperda [J.E. Smith]; FAW) resistance, desirable product profiles (PPs) and climate resilience is fundamental for food and economic security in sub‐Saharan Africa (SSA). This study reviewed and identified challenges and opportunities for effective and accelerated breeding of demand‐led maize hybrids with FAW resistance and adaptation to the diverse agro‐ecologies of SSA. Lessons were drawn on improving breeding efficiency through adequate genetic variation delivered via prebreeding programmes, speed breeding and a reduced breeding stage plan. Appropriate PPs aligned with demand‐led breeding approaches were highlighted as foundations for variety design and commercialization. Challenges to accelerated FAW resistance breeding in maize included inadequate funds and modern tools; poor adaptation of some exotic donor parental lines; lack of information on FAW resistance among local varieties; lack of integration of molecular mark...
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Papers by Cosmos Magorokosho
CW4 and CW8) seemed to be ideal parents for crosses that can do well under both the acid and non-acid soils. The best specific cross for acid soils was identified as ZW1 × CW8 (CH142512), whereas for non-acid soils, ZW3 ×CW4 (CH142500) was identified. Interestingly, the cross ZW1 × CW8 was also observed as stable under both acid and non-acid soil conditions. Overall, data showed potential of exotic acid tolerance donor lines for enhancing low-pH adaptation in sub-tropical maize populations.
Keywords: Acid soil, white maize, combining ability, genotype, acid soil tolerant donor lines (ASTDLs)
CW4 and CW8) seemed to be ideal parents for crosses that can do well under both the acid and non-acid soils. The best specific cross for acid soils was identified as ZW1 × CW8 (CH142512), whereas for non-acid soils, ZW3 ×CW4 (CH142500) was identified. Interestingly, the cross ZW1 × CW8 was also observed as stable under both acid and non-acid soil conditions. Overall, data showed potential of exotic acid tolerance donor lines for enhancing low-pH adaptation in sub-tropical maize populations.
Keywords: Acid soil, white maize, combining ability, genotype, acid soil tolerant donor lines (ASTDLs)