Maize Improvement Programs Research Articles

Pest Risk Analysis and Quarantine Precautions for Maize Importation into Ethiopia: A Case of Eleven Source Countries

Maize improvement program in Ethiopia utilizes a large amount of germplasm from external sources. Seed samples were imported from eleven different countries Mexico, Kenya, Zimbabwe, India, Norway, Colombia, Thailand, Zambia, South Africa, Nigeria and Egypt from 2011 to 2020. During maize importation, regular inspection was carried out at Holetta Agricultural Research Center for freedom from pests of insects, pathogens and weed seeds. In order to be effective in this important regulatory pest management undertaking, this review attempts to provide a concerted approach for effecting pre- and post-entry regulatory measures for maize importation into Ethiopia based on pest risk analysis (PRA) to safeguard the country. A total of 18 pests (including 12 arthropods, 3 fungi, 1 bacterium, 1 virus and 1 Spiroplasma) are of quarantine concern when importing maize seed into Ethiopia from the eleven major germplasm source-countries considered in this PRA. Three fungi (Cocliobolus, Fusarium and Mycosphaerella), one bacterium bacterial wilt of maize (Pantoea stewartii) and the virus maize chlorotic dwarf virus and corn stunt Spiroplasma (Spiroplasma kunkelii) and also twelve arthropods are of quarantine concern to the country. The number and species of pests of quarantine concern for the country vary depending on country of origin the highest in Mexico with 11 pests followed by India (7 pests) and then Colombia (6 pests). The rest consists of only 1–5 pests of quarantine importance for Ethiopia. Therefore, this review describes quarantine precautions in the import control scenarios and presents PRA based on pathway analysis for importing maize seed into Ethiopia from eleven major source-countries. Generally, the importers of maize into Ethiopia need to strictly consider the information provided in this paper before, during and after arrival of maize samples for research.

Characterization of a source of resistance to aflatoxin accumulation in maize

AbstractAflatoxinproduced by the fungus Aspergillus flavus (Link:Fr) can accumulate in maize (Zea mays L.) and poses serious human health and economic concerns, especially in sub‐Saharan Africa. Genetic resistance against A. flavus infection and spread, and subsequent production of aflatoxin, is a key tool for reducing the problem. Some resistant inbred donor lines carry quantitative trait loci (QTL) for resistance that have a sufficiently large phenotypic effect to be used for marker assisted introgression. New sources of resistance, unrelated to previously characterized resistant lines, could carry unique QTL with large phenotypic effect on resistance to complement the previously identified QTL. To this end, CML69, derived from Caribbean Composite germplasm unrelated to previously released resistant lines, was used in QTL mapping to identify and characterize new resistance QTL. Seventeen QTL were identified, although some may be the same genetic region causing QTL identified in more than one environment, indicating that these QTL are stably expressed across environments. These QTL explained 1.8–12.6% each and jointly up to 55% of the phenotypic variation. The largest effect QTL, in particular the QTL in bin 4.08, are most likely the same as has been reported in QTL mapping studies of other resistant maize lines, suggesting both environmental and genetic stability. This stability will be very useful when these QTL are used in maize improvement programs, and single nucleotide polymorphism (SNP) markers linked to these QTL were identified to facilitate this use. CML69, and other lines related to it by pedigree, may make good parents for new aflatoxin resistant hybrids.

Genomic Analysis of Selected Maize Landraces from Sahel and Coastal West Africa Reveals Their Variability and Potential for Genetic Enhancement

Genetic adaptation of maize to the increasingly unpredictable climatic conditions is an essential prerequisite for achievement of food security and sustainable development goals in sub-Saharan Africa. The landraces of maize; which have not served as sources of improved germplasm; are invaluable sources of novel genetic variability crucial for achieving this objective. The overall goal of this study was to assess the genetic diversity and population structure of a maize panel of 208 accessions; comprising landrace gene pools from Burkina Faso (58), Ghana (43), and Togo (89), together with reference populations (18) from the maize improvement program of the International Institute of Tropical Agriculture (IITA). Genotyping the maize panel with 5974 DArTseq-SNP markers revealed immense genetic diversity indicated by average expected heterozygosity (0.36), observed heterozygosity (0.5), and polymorphic information content (0.29). Model-based population structure; neighbor-joining tree; discriminant analysis of principal component; and principal coordinate analyses all separated the maize panel into three major sub-populations; each capable of providing a wide range of allelic variation. Analysis of molecular variance (AMOVA) showed that 86% of the variation was within individuals; while 14% was attributable to differences among gene pools. The Burkinabe gene pool was strongly differentiated from all the others (genetic differentiation values >0.20), with no gene flow (Nm) to the reference populations (Nm = 0.98). Thus; this gene pool could be a target for novel genetic variation for maize improvement. The results of the present study confirmed the potential of this maize panel as an invaluable genetic resource for future design of association mapping studies to speed-up the introgression of this novel variation into the existing breeding pipelines.

Revealing the genetic diversity of maize (Zea mays L.) populations by phenotypic traits and DArTseq markers for variable resistance to fall armyworm

The fall armyworm (FAW) is a gregarious insect pest causing substantial yield losses and crop failures in maize and related cereal crops in sub-Saharan Africa due to a lack of resistant varieties and integrated control options. Genetic variation for economic traits including resistance to the FAW damage is a prerequisite in maize improvement programs. The objective of this study was to determine the genetic diversity of 59 maize genotypes of diverse genetic background with variable resistance to fall armyworm, using phenotypic traits and SNP-based DArT markers. The test genotypes were profiled using agro-morphological traits, FAW damage parameters, and Diversity Array Technology Sequencing-derived single nucleotide polymorphism (SNP) markers. Significant (p < 0.001) differences were observed among the genotypes for 13 phenotypic traits with phenotypic coefficient of variation ranging from 2.19 to 51.79%. Notable phenotypic variation was observed for ear position, grain yield, FAW induced leaf and cob damage. The mean gene diversity and polymorphic information content were 0.29 and 0.23, respectively, reflecting a moderate level of genetic variation among the test genotypes when assessed using SNP markers. Analysis of the molecular variance revealed greater genetic variance within a population rather than between populations. Population structure and cluster analysis grouped the test populations into two main clusters. The following genetically divergent open pollinated varieties were selected with favourable agronomic performance and FAW resistance for population improvement or hybrid breeding: Pool 16, ZM 4236 and ZM 7114. The genetic diversity detected within and among the tested populations will facilitate the breeding of maize varieties incorporating farmer-preferred agronomic traits and FAW resistance in Zambia and related agro-ecologies.

Genetic diversity among early provitamin A quality protein maize inbred lines and the performance of derived hybrids under contrasting nitrogen environments

BackgroundInformation on population structure and genetic diversity of germplasm in a breeding programme is useful because it enhances judicious utilisation of genetic resources to achieve breeding objectives. Seventy early maturing provitamin A (PVA) quality protein maize (QPM) inbreds developed by the IITA- maize improvement programme were genotyped using 8171 DArTseq markers. Furthermore, 96 hybrids derived from 24 selected inbreds plus four checks were evaluated under low-N and optimal environments in Nigeria during 2016 and 2017. Genotypic and phenotypic data of inbreds and hybrids respectively, were analysed to (i) assess the level of genetic dissimilarities and population structure of the inbreds, and (ii) investigate the grain yield performance of derived hybrids under low-N, optimal and across environments.ResultsGenetic diversity among the seventy inbreds was high varying from 0.042 to 0.500 with an average of 0.357. Sixty-six inbred lines with probabilities ≥0.70 were assigned to a single group. The population structure analysis, the UPGMA phylogeny, and the principal Coordinate Analysis (PCoA) of the DArTseq markers revealed a clear separation of five groups and each followed pedigree records. Clustered inbreds displayed common characteristics including high PVA levels, and drought and low-N tolerance. The top performing hybrid, TZEIORQ 40 × TZEIORQ 26 out-yielded the best hybrid control, TZEIOR 127 × TZEIOR 57 by 8, 3, and 9% under low-N, optimal, and across environments, respectively. High repeatability estimates were detected for grain yield under each and across environments. Similarly, high breeding efficiency of 71, 70 and 72% were computed under low-N, optimal, and across environments, respectively.ConclusionsThe UPGMA clustering, the structure analysis, and the PCoA consistently revealed five groups which largely followed pedigree information indicating the existence of genetically distinct groups in the inbred lines. High repeatability and breeding efficiency values estimated for grain yield of hybrids under low-N, optimal and across environments demonstrated that high productive hybrids could be developed using inbreds from the opposing clusters identified by the DArTseq markers. The 15 top performing hybrids identified, particularly TZEIORQ 40 × TZEIORQ 26 and TZEIORQ 29 × TZEIORQ 43 should be further evaluated for release and commercialization in SSA.

Assessment of Genetic Diversity for Drought, Heat and Combined Drought and Heat Stress Tolerance in Early Maturing Maize Landraces.

Climate change is expected to aggravate the effects of drought, heat and combined drought and heat stresses. An important step in developing ‘climate smart’ maize varieties is to identify germplasm with good levels of tolerance to the abiotic stresses. The primary objective of this study was to identify landraces with combined high yield potential and desirable secondary traits under drought, heat and combined drought and heat stresses. Thirty-three landraces from Burkina Faso (6), Ghana (6) and Togo (21), and three drought-tolerant populations/varieties from the Maize Improvement Program at the International Institute of Tropical Agriculture were evaluated under three conditions, namely managed drought stress, heat stress and combined drought and heat stress, with optimal growing conditions as control, for two years. The phenotypic and genetic correlations between grain yield of the different treatments were very weak, suggesting the presence of independent genetic control of yield to these stresses. However, grain yield under heat and combined drought and heat stresses were highly and positively correlated, indicating that heat-tolerant genotypes would most likely tolerate combined drought and stress. Yield reduction averaged 46% under managed drought stress, 55% under heat stress, and 66% under combined drought and heat stress, which reflected hypo-additive effect of drought and heat stress on grain yield of the maize accessions. Accession GH-3505 was highly tolerant to drought, while GH-4859 and TZm-1353 were tolerant to the three stresses. These landrace accessions can be invaluable sources of genes/alleles for breeding for adaptation of maize to climate change.

An Integrated Molecular and Conventional Breeding Scheme for Enhancing Genetic Gain in Maize in Africa.

Maize production in West and Central Africa (WCA) is constrained by a wide range of interacting stresses that keep productivity below potential yields. Among the many problems afflicting maize production in WCA, drought, foliar diseases, and parasitic weeds are the most critical. Several decades of efforts devoted to the genetic improvement of maize have resulted in remarkable genetic gain, leading to increased yields of maize on farmers’ fields. The revolution unfolding in the areas of genomics, bioinformatics, and phenomics is generating innovative tools, resources, and technologies for transforming crop breeding programs. It is envisaged that such tools will be integrated within maize breeding programs, thereby advancing these programs and addressing current and future challenges. Accordingly, the maize improvement program within International Institute of Tropical Agriculture (IITA) is undergoing a process of modernization through the introduction of innovative tools and new schemes that are expected to enhance genetic gains and impact on smallholder farmers in the region. Genomic tools enable genetic dissections of complex traits and promote an understanding of the physiological basis of key agronomic and nutritional quality traits. Marker-aided selection and genome-wide selection schemes are being implemented to accelerate genetic gain relating to yield, resilience, and nutritional quality. Therefore, strategies that effectively combine genotypic information with data from field phenotyping and laboratory-based analysis are currently being optimized. Molecular breeding, guided by methodically defined product profiles tailored to different agroecological zones and conditions of climate change, supported by state-of-the-art decision-making tools, is pivotal for the advancement of modern, genomics-aided maize improvement programs. Accelerated genetic gain, in turn, catalyzes a faster variety replacement rate. It is critical to forge and strengthen partnerships for enhancing the impacts of breeding products on farmers’ livelihood. IITA has well-established channels for delivering its research products/technologies to partner organizations for further testing, multiplication, and dissemination across various countries within the subregion. Capacity building of national agricultural research system (NARS) will facilitate the smooth transfer of technologies and best practices from IITA and its partners.

Phenotypic characterization of maize landraces from Sahel and Coastal West Africa reveals marked diversity and potential for genetic improvement

ABSTRACTLandraces of maize (Zea mays L.) are invaluable sources of genetic variability for improving agronomic traits, and they hold great promise in developing new maize varieties with enhanced resilience to stresses. Even though phenotypic characterization is an inexpensive approach for elucidating variation hidden in genetic resources, information on the genetic diversity patterns in large collections of landraces remains limited and this constitutes a major impediment for their optimal utilization in modern maize breeding programs. We investigated the extent of phenotypic diversity among 196 maize landraces, representing gene pools from Burkina Faso, Ghana and Togo, and 14 improved populations/varieties from the Maize Improvement Program of International Institute of Tropical Agriculture (IITA-MIP). The germplasm was assessed for 26 agronomic traits. Highly significant differences (P < 0.001) were observed among the accessions for all measured traits. Cluster analysis separated the maize germplasm into five major groups, differentiated largely by phenology and overall phenotypic appeal, enabling identification of outstanding genotypes for further screening for stress tolerance. Wide genetic diversity was observed between Burkinabe and improved gene pools, suggesting that the original Sahelian gene pool might not have contributed much to modern cultivars. This gene pool offers opportunities for pre-breeding by providing novel alleles for enriching elite maize germplasm. Shannon-Weaver diversity index (H’) revealed high genetic variability among the landraces (H’ = 0.73) and a narrow genetic base in the improved populations and varieties (H’ = 0.46). These results provide new insights into the potential of tropical maize landraces for genetic improvement of maize.

Genetic Diversity among Tropical Provitamin A Maize Inbred Lines and Implications for a Biofortification Program

Insights into the diversity and relationships among elite breeding materials are an important component in maize improvement programs. We genotyped 63 inbred lines bred for high levels of provitamin A using 137 single nucleotide polymorphism markers. A total of 272 alleles were detected with gene diversity of 0.36. Average genetic distance was 0.36 with 56% of the pairs of lines having between 0.30 and 0.40. Eighty-six percent of the pairs of lines showed relative kinship values <0.50, which indicated that the majority of these provitamin A inbred lines were unique. Relationship pattern and population structure analysis revealed presence of seven major groups with good agreement with Neighbour Joining clustering and somewhat correlated with pedigree and breeding origin. Utilization of this set of provitamin A lines in a new biofortification program will be aided by information from both molecular-based grouping and pedigree analysis. The results should guide breeders in selecting parents for hybrid formation and testing as a short-term objective, and parents with diverse alleles for new breeding starts as a long-term objective in a provitamin A breeding program.

Enhance Maize &lt;i&gt;(Zea mays L.)&lt;/i&gt; Tolerance to Abiotic Stress Through the Genetic Transformation with Anthranilate Synthase (ASA2 Gene) Using Particle Bombardment

The agricultural plans in Egypt aim to increase maize production and yield to reduce the importation and to meet the country's need from maize. Currently the crop production is affected by the climatic changes which rise the abiotic and biotic stresses problems. In an attempt to raise the tryptophan level in maize, particle bombardment technique was used with two hybrids maize, namely Sc168 and Sc10. The results of this study showed that both hybrids were transformed efficiently and showed increased levels of tryptophan in the two hybrids. The double shot 1100 psi was higher effective than single shot. It can be concluded that levels of tryptophan increased clearly in the two hybrids which is considered an indicator for ASA2 successful expressing as compared to control. The present study established effective tissue culture protocol for maize hybrids suitable for gene transformation which may used in maize improvement programs in the future.

Ovary abortion is prevalent in diverse maize inbred lines and is under genetic control

Crop improvement programs focus on characteristics that are important for plant productivity. Typically genes underlying these traits are identified and stacked to create improved cultivars. Hence, identification of valuable traits for plant productivity is critical for plant improvement. Here we describe an important characteristic for maize productivity. Despite the fact mature maize ears are typically covered with kernels, we find that only a fraction of ovaries give rise to mature kernels. Non-developed ovaries degenerate while neighboring fertilized ovaries produce kernels that fill the ear. Abortion occurs throughout the ear, not just at the tip. We show that the fraction of aborted ovaries/kernels is genetically controlled and varies widely among maize lines, and low abortion genotypes are rare. Reducing or eliminating ovary abortion could substantially increase yield, making this characteristic a new target for selection in maize improvement programs.

Improving Breeding Efficiency of a Hybrid Maize Breeding Program Using a Three Heterotic‐Group Classification

Core Ideas Maize breeding efficiency can be greatly improved by adopting three heterotic groups in hybrid breeding. Using three heterotic groups improves maize breeding efficiency for using genetic resources. General breeding efficiency is used to measure efficiency of genetic resource usage, and specific breeding efficiency is to obtain maximum output with inputs. Suwan1 is an important heterotic group from tropical/subtropical and should be explore more worldwide. Heterotic group classification has a crucial impact on maize (Zea mays L.) breeding efficiency in a hybrid‐based breeding program. The objectives of this study were to: (i) investigate whether or not breeding efficiency could be improved using a three heterotic‐group (TriHG) classification (Reid and non‐Reid, and Suwan1 heterotic groups) system instead of a usual two heterotic‐group (DiHG) classification (Reid and non‐Reid heterotic groups) system; and (ii) estimate the impact of TriHG and DiHG systems on breeding efficiency, utilizing the same data in computing specific breeding efficiency (SBE) and general breeding efficiency (GBE) in a subtropical breeding program in southern China. Twenty‐five adapted tropical and subtropical lines were crossed to six testers using a line × tester mating design. Data on grain yield were used to calculate SBE and GBE for comparing DiHG‐ and TriHG‐based strategies. The TriHG classification system increased GBE by 77.8% over the DiHG system without a significant loss in SBE. We concluded that the TriHG system was better than the DiHG system for improving maize‐breeding efficiency. Therefore, maize breeders may re‐think their breeding strategy for improving breeding efficiency in long‐term breeding programs by adopting the suggested TriHG system. Hybrid maize improvement programs, especially in the early stages of breeding for identifying hybrids with high yield potential, can be become more efficient by using three testers with one from each of Reid, nonReid, and Suwan1 heterotic groups. This would improve the chances of developing high‐yielding hybrids in a breeding program with the available, diverse germplasm.

Quantitative studies on heterosis and inbreeding depression in maize (Zea mays l.)

The present investigation was carried out for studying heterosis and inbreeding depression of twenty eight hybrids (F1 ? s) and their F2 ? s made by crossing of eight maize inbreds in all possible cross combinations excluding reciprocal. Observations were recorded on ten quantitative traits viz., plant height (cm), ear length (cm), ear girth (cm), number of kernel rows per ear, number of kernels per row, 100 kernels weight (g) yield per plant (g), days to 50 % tassel emergence, days to 50% silk emergence and days to 50% maturity. Variable magnitude of heterosis was observed for different cross combinations for all the traits. Based on higher mean performance (94.33 to 118.67 g/plant) and higher heterotic response (11.95 to 30.48%) eleven crosses were selected. Response of inbreeding depression was significant in positive direction for most of the traits. Among these eleven crosses five crosses CM 300 x CML 142, CM 300 x CML 144, CM 300 x CML 150, CM 300 x CML 176 and CML 150 x CML 144 were selected having high heterotic value (12.31 to 30.48%) and lower inbreeding depression (less than 15%) for their utilization in maize improvement programme for the development of superior inbred lines.

Genomic-based-breeding tools for tropical maize improvement.

Maize has traditionally been the main staple diet in the Southern Asia and Sub-Saharan Africa and widely grown by millions of resource poor small scale farmers. Approximately, 35.4million hectares are sown to tropical maize, constituting around 59% of the developing worlds. Tropical maize encounters tremendous challenges besides poor agro-climatic situations with average yields recorded <3tones/hectare that is far less than the average of developed countries. On the contrary to poor yields, the demand for maize as food, feed, and fuel is continuously increasing in these regions. Heterosis breeding introduced in early 90s improved maize yields significantly, but genetic gains is still a mirage, particularly for crop growing under marginal environments. Application of molecular markers has accelerated the pace of maize breeding to some extent. The availability of array of sequencing and genotyping technologies offers unrivalled service to improve precision in maize-breeding programs through modern approaches such as genomic selection, genome-wide association studies, bulk segregant analysis-based sequencing approaches, etc. Superior alleles underlying complex traits can easily be identified and introgressed efficiently using these sequence-based approaches. Integration of genomic tools and techniques with advanced genetic resources such as nested association mapping and backcross nested association mapping could certainly address the genetic issues in maize improvement programs in developing countries. Huge diversity in tropical maize and its inherent capacity for doubled haploid technology offers advantage to apply the next generation genomic tools for accelerating production in marginal environments of tropical and subtropical world. Precision in phenotyping is the key for success of any molecular-breeding approach. This article reviews genomic technologies and their application to improve agronomic traits in tropical maize breeding has been reviewed in detail.

BIOCHEMICAL AND MOLECULAR IDENTIFICATION OF SIX MAIZE INBRED LINES

The present investigation was done to define the identity of six maize inbred lines using SDS-PAGE protein analysis and some isozymes variability, DNA fingerprinting detected by inter simple sequence repeat (ISSR)-PCR molecular markers. Protein electrophoresis revealed that total number of bands ranged from 12 in the inbred line Sids 1108 to 4 in inbred line Sids 1157 and inbred line Sids 63. Three common bands were found in all tested inbred lines. Two inbred lines; Sids 7 and Sids 1108 showed specific bands which could be used to distinguish them from the others. In addition, bands of two isozymes systems, peroxidase (Prx) and esterase (EST) were determined for the six maize inbred lines based on polyacrylamide gel electrophoresis. The number of bands and Rf values could be used to identify these inbred lines. Eleveen anchored ISSR primers were used for fingerprinting of the six maize inbred lines and obtained 73 scorable bands, 42 of them were polymorphic (58 %). Sids 7 produced two bands with two primers (ISSR 1and ISSR 10). Sids 34 produced three bands with three primers (ISSR 1, ISSR 9 and ISSR 11). Sids 1159 produced three bands with three primers (ISSR 2, ISSR3 and ISSR 8). Sids 1108 produced two bands with two primers (ISSR 6 and ISSR 7). Sids 1157 have one band marker with primer ISSR 11. Also, Sids 63 has one band marker with primer ISSR 3. Existing genetic differences between inbred lines are important from the point of view of the breeder to take advantage in maize improvement programs.

Agunas reflexiones sobre el PCCMCA

As I look back over the 35 years of development of the PCCMCA, its success and accomplishments have definitely been a real source of satisfaction to me and I believe to all participants. The mere fact that it is going stronger than ever after 35 years of operation is in itself a highly significant sign of its success. The PCCMCA not only sparked the modem developments of agricultural production in Central America and Panama, but it also ranks high as one of the successful operational models in the agricultural revolution of the Third World. Regional maize programs in the Andean Zone and Southeast Asia were soon patterned after it. Even more impressive, it provided a basic pattern for a whole series of interacting collaborative regional research programs widely promoted by the International Research Centers around the world. This is something of which the Central American agricultural and development workers can be proud. As a matter of fact, all participants can feel doubly proud because in the development of this highly successful approach they had no precedent to follow. They relied on enthusiasm, common sense and hard work. They were generous with their certificates of recognition for all those who helped, regardless of nationality or institutional affiliations both from within and outside the region.¿HOW DID IT ALL GET STARTED?It all got started when seven people met in Turrialba in 1954 (one representative from each of the six middle American countries and a representative of the “Oficina de Estudios Especiales”, OEE, in México) to talk about the possibilities of starting a Central American Cooperative Maize Improvement program.

Phenotypic Variability of Some Maize Inbreed Lines from ARDS Turda

The inbreed lines collection from the Agricultural Reseach and Development Station Turda include inbreed lines created on the station, but also lines with a different origin.The aim of this paper is the study of the phenotypic variability between maize inbreed lines for vegetative traits of the plant and the traits of ear and kernels: plant height, ear height, number of leaves/plant, number of branches/tassel, reaction to different types of cms, ear lenght, number of rows, number of kernels/row, kernels type, kernels color, cob color and the chemical composition of the grains. Using the phenotypic characterisation there are identified new sources for some favorable traits that can be used for the breeding of competitive hybrids. The study also refered to the number of days between sowing to silking, and sowing to physiological maturity. On this study there were analyzed over 471 dent and flint inbreed lines from ARDS Turda. The inbreed lines were studied on the field regarding vegetative traits: the plant height, the ear height, number of leaves/plant and the number of branches/tassel. On the laboratory there were studied the ear and kernels traits. Using all the data obtained there will be choosen some inbreed lines that are used for the maize hybrids breeding programs. Most inbreed lines belong to the dent variety and most lines have a short or medium long ear. It was also noticed a high proportion of lines with 14-18 kernel rows. There is a high variability between the lines regarding the plant height, ear hight and the number of kernels/row, and a very high variability for the number of branches/tassel. The inbreed lines from ARDS Turda can be used as parents for the commercial hybrids. The variability between the lines makes them more valuable, due to the fact that there are a lot of sources for maize improvement programs.

Assessing the representativeness and repeatability of testing sites for drought-tolerant maize in West Africa

Badu-Apraku, B., Akinwale, R. O., Obeng-antwi, K., Haruna, A., Kanton, R., Usman, I., Ado, S. G., Coulibaly, N., Yallou, G. C. and Oyekunle, M. 2013. Assessing the representativeness and repeatability of testing sites for drought-tolerant maize in West Africa. Can. J. Plant Sci. 93: 699–714. The selection of suitable breeding and testing sites is crucial to the success of a maize (Zea mays L.) improvement programme. Twelve early-maturing maize cultivars were evaluated for 3 yr at 16 locations in West Africa to determine the representativeness, discriminating ability, and repeatability of the testing sites and to identify core testing sites. Genotype main effect plus genotype by environment interaction (GGE) biplot analysis revealed that Zaria (Nigeria), Nyankpala (Ghana), and Ejura (Ghana) displayed the highest discriminating ability. Two mega-environments were identified. Bagou, Nyankpala, Bagauda, Ikenne, and Mokwa constituted the first mega-environment (ME1); Ejura, Ina and Sotuba represented the second (ME2). The ME1 would be more useful for evaluating early maize genotypes for tolerance to drought than ME2 because locations in ME1 were more strongly correlated to Ikenne (managed drought stress site). Among the test locations, Bagou and Mokwa were found to be closely related to Ikenne in their ranking of the cultivars for drought tolerance; Zaria was the exact opposite, indicating that this was the least suitable location for evaluating genotypes for drought tolerance. Nyankpala and Ikenne were identified as the core testing sites for ME1 and Ejura for ME2. TZE Comp 3 C2F2 was identified as the highest yielding cultivar for ME1 and Syn DTE STR-Y for ME2, indicating that they could be used as check cultivars. Ikenne, Nyankpala, and Ejura had moderately high repeatability. They were closer to the average environment axis of each mega-environment and will be useful for culling unstable genotypes during multi-locational testing. Other sites were less representative and not repeatable and will not be useful for evaluating early maize cultivars for drought tolerance.

Comparison of the Performance of Best Linear Unbiased Estimation and Best Linear Unbiased Prediction of Genotype Effects from Zoned Indian Maize Data

ABSTRACTThe maize (Zea mays L.) growing area in India is divided into five zones for cultivar testing. During triannual testing of genotypes in official trials within the All‐India Coordinated Maize Improvement Program (AICMIP), a large number of entries is rejected each year. Therefore, only a low number of entries is carried forward to the advanced stage of testing. The subdivision of the breeding sites into zones results in limited data per zone. Hence, the question arises how to select the best genotypes per zone and how information can be borrowed across zones to improve the accuracy of selection within zones. We compared the performance of best linear unbiased prediction (BLUP) using the correlation of genetic effects between zones with best linear unbiased estimation (BLUE) based on data per zone. In both cases, data were analyzed using a mixed model. We used simulations to calculate correlations between the true simulated values and the predicted genotype values obtained by BLUE and BLUP using the same models. The data structure and the variance components used in simulations were based on the analysis of 40 triannual series of four different maize maturity groups. Best linear unbiased prediction outperformed BLUE in 38 out of 40 series and on average across all series. An advantage of BLUP was observed for varying genetic correlations between zones. We conclude that the use of BLUP enhanced the estimation accuracy in zoned AICMIP maize testing trials and can be recommended for future use in these trials.

Heterosis and interrelationship study on the values of the maize Kernel’s major ingredients and its thousand weight

Five inbreds (UDL1, UDL4, UDL5, UDL6, 126) from our preliminary maize improvement program for increased starch content and some of their hybrids were grown in 2008 at the field of Horticultural Institute, Debrecen University. Three chemical parameters (starch-, protein-, oil content) and the weighing of one physical trait (thousand-kernel weight) were analyzed. The starch content varied from 64.29–70.80% in lines and from 70.84–72.29% in case of hybrids. Protein content in the dry material was between 9.04–12.62% in case of the parent lines and it was 7.61–9.56% in the single cross hybrids. Strong negative correlation (r = −0.834**) was found between starch and protein content of the examined hybrids. The oil content varied from 2.70–3.64% and 2.87–3.39% in lines and hybrids, respectively. The thousand-kernel weight (TKW) varied between 213.6–341.3 g in case of the lines and it was 314.3-426.3 g in hybrids. Significant differences were found among hybrids in TKW (SD5% = 34.66%). Heterosis was experienced in the starch content of UDH6 hybrid. Both the relative and absolute values of heterosis for starch content and kernel weight were positive for each single cross hybrid.