54 research outputs found
Evaluation and identification of single-cross maize hybrids for use in tester development.
No full textMaster of Science in Plant Breeding. University of KwaZulu-Natal, Pietermaritzburg, 2018.Development of testers from new inbred lines that are high yielding and high discriminating abilities in diverse environments, and in stress conditions is very important in maize breeding in southern and eastern Africa. Genetic gain decreases when new lines are combined with old testers. It is, therefore, important to develop new testers that perform better in harsh environmental conditions to replace the old single-cross testers; CML 312 x CML 442 (heterotic group A) and CML 444 x CML 395 (heterotic group B). These are currently dominating the maize breeding programmes at the Agricultural Research Council (ARC) and most of the National Agricultural Research stations (NARS) in eastern and southern Africa. The objectives of this study were therefore; i) to identify elite single-cross hybrids suitable for further evaluation as potential testers in development of three-way cross hybrids, ii) to determine the correlations between grain yield and secondary traits in single-cross maize hybrids, and iii) to estimate phenotypic and genetic variance components, heritability and genetic advances for yield and its related components in single-cross maize hybrids. The trials were established under three different environments which are: random drought (RD), optimum environment (OPT) and low nitrogen (Low N) at ARC Potchefstroom and Cedara using alpha lattice 0, 1 design (32 x 5). The single-cross hybrids used in this study were obtained from CIMMYT Zimbabwe and they belong to two different heterotic groups as follows;, heterotic group A with 160 entries among which 155 were experimental single-cross hybrids and five were check entries and heterotic group B with 160 entries among which 157 were experimental single-cross hybrids and three were hybrid checks.
High significant differences (P< 0.01) among single-cross hybrids were observed on days to 50% anthesis (AD), grain yield (GY), ear height (EH), and ears per plant (EPP) in heterotic group B under optimum environment. Hybrid 139 had a mean yield of 8.65 t/ha, which was higher than the average grain yield of 6.22 t/ha. Days to 50% anthesis (AD), anthesis-silk interval (ASI), plant height (PH), and EH varied significantly (p<0.01) among single-cross hybrids in the low nitrogen environment. Hybrid 65 had a mean yield of 4.04 t/ha, which was higher than the average yield of 2.29 t/ha. Days to 50% anthesis were slightly higher in low nitrogen environment than in optimal environment. Hybrid 92 had a mean yield of 7.53 t/ha, which was higher than the average yield of 4.77 t/ha in random drought environment. As in heterotic group B, significant variations were observed in heterotic group A, in random drought and optimum environments. Grain yields of 9.44 t/ha and 6.42 t/ha for maize hybrids 134 and 52 were higher than average mean yields of 6.75 t/ha and 3.43 t/ha from optimum and random drought environments, respectively. Hybrids with higher trait values than the average may be advanced for further use in breeding in their respective environments. Maize single-cross hybrids 1, 23, 127, 15, 122, 8, 134, 109, 34, and 31 from heterotic group A and 69, 81, 65, 97, 92, 40, 117, 58, 101, and 44 from heterotic group B were selected for further use in breeding. The hybrids had consistently higher mean yields across the environments.
Significant, positive and negative correlations were observed among secondary traits in all environments. Yield (t/ha) was positively correlated with cob length (CBL), EH, field weight (FW), grain weight (GW) and shelling percentage (SP). It was however, negatively correlated with days to 50% silking (SD) and days to 50% anthesis (AD). A breeding programme aimed at improving CBL, EH, FW, GW and SP and reducing traits SD and AD may indirectly result in improvement of maize yields in random and optimum environments. High genotypic coefficient of variation (GCV) and phenotypic coefficient of variation (PCV) were observed for ASI, yield t/ha, PH and ear height therefore, and selection can be done. Improvement of maize yield based on AD and ASI selection would be successful due to their high broad sense heritability estimates. The genetic advance observed in this study were high and therefore some trait values can be increased in the next generation through selection
Evaluation of maize hybrids for low-nitrogen stress tolerance, yield stability and genetic purity.
No full textMasters Degree. University of KwaZulu-Natal, Pietermaritzburg.Nitrogen stress is among the major abiotic constraints that impede maize production in Africa. Therefore, development of maize varieties that are tolerant to low N stress conditions and stable across environments is needed. Assessment of genetic purity of inbred lines and their F1 hybrids is among the quality control measures in hybrid breeding, seed production, variety release as well as intellectual property protection (IP). The objectives of this research were, therefore: a) to assess the grain yield performance, genetic parameter estimates, correlations and conduct path coefficient analysis for grain yield and related traits under low N and optimum conditions, b) to assess the magnitude of genotype by environmental interaction (GEI) and hybrid yield stability under low N and optimum conditions and c) to assess the genetic purity of maize parental lines and their F1 hybrids. To achieve these objectives, 170 single cross maize hybrids were evaluated across low N and optimum environments at three locations in South Africa (SA) during 2017/18 summer season viz. Potchefstroom, Vaalharts and Cedara. The experimental setup comprised of five-production conditions across these three locations. The collected data was subjected to analyses using Genstat software 18th edition, SPSS version 25 and SAS version 9.3. For genetic purity analysis, 158 single-cross maize hybrids along with 30 elite parental inbred lines were genotyped using 92 SNPs markers and the molecular data was analysed using GenAlex software.
Results revealed that variance due to environment, genotype and GEI were highly significant (P 5% hence not pure. Cluster analysis effectively discriminated the parental lines into three distinct genetic clusters. Parent-offspring test conducted on 158 hybrids resulted to the elimination of 38% of the hybrids due to genetic contamination of their parental inbred lines. Of the 68 hybrids that passed the parent-offspring test, seven hybrids, including SCHP29, SCHP95, SCHP94, SCHP134, SCHP44, SCHP114 and SCHP126, were selected as potential candidates for further evaluation and possible release in South Africa due to their outstanding yield performance
Determining heterotic orientation of South African maize inbred lines towards USA temperate and CIMMYT- tropical testers and genetic analyses under contrasting environments.
No full textDoctoral Degree. University of KwaZulu-Natal, Pietermaritzburg.Drought and low soil fertility are major abiotic stresses limiting maize productivity in South Africa.
Developing drought and low nitrogen-tolerant varieties is part of a long-term solution to improved
maize productivity under climate change. The employment of well-defined heterotic groups has
been the prime cause of success of most hybrid breeding programs in the private sector. The
public maize program in South Africa utilises seven heterotic groups. These require many different
testers, and the resultant many cross combinations require a lot of resources for extensive field
testing. Reducing the number of heterotic groups is essential for improving breeding efficiency.
The objectives of this study were to classify the South Africa maize inbred lines into fewer heterotic
groups based on their orientation towards temperate and tropical testers, and to identify superior
genotypes under stress and non-stress environments. A sample of 42 lines drawn from the seven
heterotic groups was genotyped with 56110 SNP DNA markers. The lines were also crossed to
two inbred line testers representing the heterotic groups A and B for tropical CIMMYT and
temperate USA Corn Belt. The resultant hybrids were evaluated in an (0, 1) α-lattice design under
stress and non-stress conditions during the 2014/15 and 2015/16 summer seasons. Data were
collected on grain yield and secondary traits. Using the specific combining ability and SNP-marker
data, the seven heterotic groups could be reorganised into two major clusters. This information
would be useful in designing superior hybrids. Correlation between genetic distance with grain
yield and specific combining ability was negligible, making it prudent to perform multi-location
trials to identify superior genotypes. The lines FO215W, I-42, I-16 and K64 displayed good
general combining ability for grain yield. The most superior hybrids were FO215W x CML444 and
I-42 x CML444, which combined high productivity with stability. However, performance of hybrids
generally differed under stress and non-stress conditions. Overall, results showed success in
simplifying the heterotic grouping of the public maize germplasm in South Africa and the possibility
of improving heterosis and obtaining high yields under low input and water limited environments
by exploiting temperate × tropical hybrid combinations
Evaluation of early maturing maize (zea mays L.) hybrids for multiple-stress tolerance.
No full textMasters Degree. University of KwaZulu-Natal, Pietermaritzburg.Maize (Zea mays L.) is the most important cereal in Africa, but a number of constraints including biotic, abiotic and socio-economic factors affect its production. The abiotic factors such as drought, low nitrogen (N) and heat contribute to the low grain yield production, which creates a challenge that needs to be addressed by researchers. Thus, development and use of early maturing maize hybrids could help in stabilizing maize production. Early maturing maize hybrids help in reducing the growing period to escape some of the abiotic stresses that contains variability for high yield potential and adaptive traits. This study, therefore, was aimed at breeding and identifying early maturing maize hybrids cultivars that are tolerant to drought and low N stresses. Fifty early maturing maize hybrids including six commercial checks were evaluated under stress and non-stress environments during the 2016/17 maize growing season in South Africa. The objectives were (i) to estimate variance components, correlation and path coefficients among grain yield and secondary traits in early maturing maize hybrids across stress and non-stress environments and (ii) to evaluate genotype by environment interaction effects and stability for grain yield performance in early maturing maize hybrids across stress and non-stress environments.
To estimate the variance components, correlation and path coefficients among grain yield and secondary traits in early maturing maize hybrids across stress and non-stress environments, quantitative traits data including grain yield and its secondary components were recorded. Statistical analyses revealed that the effect of genotype, environment and genotype by environment interaction were significant (P<0.01) for all the traits. Hybrids CZH16084, CZH16064 and CZH16095 under managed drought, low N and optimum environments, respectively, were identified as the outstanding genotypes for grain yield and recommended for further testing, release and registration. High magnitude of phenotypic and genotypic coefficient of variation as well as high heritability were recorded for each single environment for anthesis days, silking days, ear height and plant height, suggesting that those traits interacted with the environment. Grain yield was positively correlated with anthesis days and ear height, field weight, grain moisture at Potchefstroom while at Lutzville and Cedara had negative correlation with those traits, suggesting that the genotypes differed significantly for most of the phenotypic traits. Path coefficient analyses revealed that anthesis days and anthesis-silking interval had positive direct effects while silking days, plant height and ear per plant had a negative direct effect on grain yield in all the environments. These traits are recommended for effective selection to the improvement of maize grain yield.
To evaluate genotype by environment interaction effects and stability for grain yield performance in early maturing maize hybrids across stress and non-stress environments, data collected from all environments which were Lutzville (managed drought), Potchefstroom (optimum), Cedara (optimum) and Cedara (low nitrogen) during the 2016/17 summer planting season, were subjected to ANOVA and GGE biplot analyses. Analysis of variance for individual environments showed that the genotype mean squares were significant at P<0.01. The ANOVA across environments showed that the genotype, environment and genotype by environment interaction mean squares were significant at P<0.01 for grain yield. From the GGE biplot analysis, the two principal components (PC1 and PC2) contributed 64.8% of the total variability due to genotypes plus genotype by environment interaction, with PC1 and PC2 accounting for 35.97% and 28.83%, respectively. The use of GGE biplot analyses provided a clear basis for determining the stability and performance of the 50 early maize hybrids and ranked them according to order. The best performing genotypes were G13 (CZH15448), G46 (CZH15574), G15 (local check 2), G33 (CZH16094), G7 (CZH16083), G20 (CZH16090) and G4 (CZH16089). The following hybrids were adapted to specific environments as follows: G26 (CZH16070), G34 (CZH16074), G9 (CZH15499) and G18(CZH16071) at Cedara (optimum) conditions; G46 (CZH15574), G40 (CZH16069) and G12 (CZH16080) excluding the checks G23 (local check 1) and G14 (SC301) at Potchefstroom (optimum); G22 (CZH16093), G6 (CZH15575), G49 (CZH16068) and G17 (CZH15600) excluding the check G15 (local check 2) at Cedara (low N) and G33 (CZH16094), G37 (CZH15184), G41 (CZH16082), G28 (CZH16076) and G8 (CZH16065) at Lutzville (managed drought). The GGE biplot analysis also identified nine stable and high yielding genotypes, which included G6 (CZH15575), G46 (CZH15574), G22 (CZH16093), G49 (CZH16068), G12 (CZH16080), G17 (CZH15600), G28 (CZH16076), G47 (CZH15452), and G8 (CZH16065). These genotypes will contribute to high maize yields and stable grain production in specific and across environments and are therefore, recommended for further testing and release
Genotype x environment interaction, yield stability and adaption responses of 25 single-cross maize (Zea mays L.) hybrids grown in Michigan
No full textThesis (Ph. D.)--Michigan State University. Department of Crop and Soil Science, 1987Includes bibliographical references (pages 130-140
Genetic Differentiation of ARC Soybean [Glycine Max (L.) Merrill] Accessions Based on Agronomic and Nutritional Quality Traits
No full textGenetic Differentiation of ARC Soybean [Glycine Max (L.) Merrill] Accessions Based on Agronomic and Nutritional Quality Traits
No full textSoybean is one of the most important leguminous crops grown globally for food and feed. The study of genetic diversity is invaluable for efficient utilization, conservation and management of germplasm collections. The study aims at assessing genetic diversity present among the soybean genotypes using phenotypic markers. The restriction maximum likelihood revealed highly significant differences among the genotypes for eight quantitative traits. The principal component analysis revealed three most important PCs contributing 63.19%, 25.43% and 8.88% to the total variation of 97.5%, respectively. Seed yield was highly significant and highly correlated with seed number per plant, pod weight per plant, pod number per plant, and hundred seed weight but negatively correlated with seed number per pod. The hierarchical clustering revealed three major clusters with further sub-clusters. The accessions 2015/06/12, 69 S 10, PR 154-14, R 5-4-2 M, Hawkeye (USSR), and PR 145-2 were the most diverse. There were significant differences among the accessions based on nutritional quality traits such as oil, protein and stearic acid across the locations. The protein content varied from 29.1% to 35.6%, oil content varied from 10.6% to 20.7% whereas oleic acid and ash varied between 6.8% and 30.8%, and 4.3% and 8.2%, respectively. There was vast genetic diversity among the soybean genotypes. The presence of genetic diversity will aid breeders in selections and hybridization programmes for crop improvement
Seed yield and associated trait improvements in sunflower cultivars over four decades of breeding in South Africa
No full textTechnology and Customers’ Experiences in Fashion Physical Stores: The Case of Sweden
No full textTitle: Technology and Consumers’ Experiences in Fashion Physical Stores: The Case of Sweden Level: Master Thesis in Business Administration Author: Meron Kebede Abebaw; Willard Kingstone Matukuta Supervisor: Agneta Sundström, PhD Examiner: Maria Fregidou-Malama, PhD Date: May, 2018 Aim: The aim of this study is to analyze whether in-store digital technology in fashion retailers are used to change the customers’ shopping experience and behavior. Method: This study chooses qualitative research and used both primary and secondary data collection as method. Results and conclusions: This study have reached to conclude that: with the current advances in technology, physical stores can use in-store technology to give customers a new experience; physical stores perceive that using in-store digital technology will change customers shopping experience. Also, marketing mix inputs and technology affect customers’ behavior. Suggestions for future research: For future research, how smart fitting rooms may influence the customer experience in the physical store will be important to study. Researchers can also consider understanding customer responses to in-store technology. Finally, a customer’s perspective to both suggestions should improve the knowledge on whether digital solutions are preferred in in-store shopping or not. Contributions of the thesis: This thesis contributes to the current state of theories on in-store technology by showing atmosphere has effect on customers’ experiences and behavior in addition to the marketing mix. On the managerial perspective, analyzing the installation of this technology will enable to identify its effect on customers’ experiences and behavior. In addition, on the societal perspective, the behavior of customers will help in motivating younger generation to utilize this in-store technology
Contribution of temperate germplasm to the performance of maize hybrids under stress and non-stress environments in South Africa
No full textIncreases in genetic gains are crucial to maize breeding programmes. The objectives of this study were to identify higher-yielding and stable maize hybrids across stress and non-stress environments, to identify representative test environments for testing and selection of superior maize genotypes, and to determine the contribution of temperate maize germplasm in the performance of new tropical hybrids. Respectively 42 and 72 newly developed single-cross hybrids together with check hybrids were evaluated separately for grain yield performance across stress and non-stress environments, at four locations (Potchefstroom, Cedara, Vaalharts/Taung and Makhathini) in South Africa, in the 2014/15 and 2015/16 growing seasons (seasons 1 and 2, respectively). Additive main effects and multiplicative interaction (AMMI) and genotype + genotype × environment interaction (GGE) biplots were employed. In season 1, the hybrids MO17HtHtN × CML444 and I-39 × CML444 were the most stable and high-yielding genotypes after the ideal commercial check. In season 2, the hybrids FO215W × CML444, I-42 × CML444 and U71Y × CML444 were stable and high-yielding, with FO215W × CML444 being the most ideal. These stable hybrids would be the best suited for wide adaptation across non-stress and stress environments. Hybrids containing tropical CIMMYT testers were more stable than those derived from temperate Corn Belt material. The locations Potchefstroom and Vaalharts were the most suitable environments for evaluating the performance of these genotypes across the diverse environments
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