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The rising demand for maize (Zea mays L.) in West and Central Africa (WCA) requires the availability of economical, adaptable, and high-yielding hybrids in the sub-region. The screening of maize hybrids in multi-environment trials (METs) is necessary for proper varietal selection. The aim of our study was to evaluate three-way maize hybrids for stability of performance across varied agro-ecologies. Forty-five three-way maize hybrids, along with 11 commercial hybrid checks, were evaluated in Zaria (Northern Guinea Savanna), Kisi (Southern Guinea Savanna), Eruwa (Derived Savanna), and Ibadan (Rainforest transition) in Nigeria in 2015. Data on grain yield were subjected to analysis of variance (ANOVA). Genotype and genotype × environment interaction (GGE) biplot analysis was employed to explore the genotype × environment interaction (GEI). Combined ANOVA showed that variation attributable to locations, genotypes, and GEI was significant (p ≤ 0.01). Hybrid G22 had 6% to 11% yield advantage over the commercial hybrids SC719 and OBA SUPER 1, whereas hybrids G45, G44, and G42 had 18% to 22% higher yield than the commercial hybrid OBA SUPER 2. GGE biplot identified three location groups, with G46, G22, and G2 being the most adapted hybrids in their respective sectors. GGE biplot analysis adjudged G45, G14, and G13 to be the best combiners of high yield and stability across the test locations. The identified hybrids have the potential to increase maize production and meet the rising local demand for maize in WCA. [ABSTRACT FROM AUTHOR]

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The development of higher yielding maize (Zea mays L.) hybrids adapted to low input small-holder farming systems in sub-Saharan Africa is required. Three-way hybrids (i.e. F1 tester crossed to inbred line) can be produced at lower cost for smallholder farmers, but to achieve this it is crucial for CIMMYT-Zimbabwe maize breeding program to identify new high yielding single cross testers with high combining ability to support the development of new high yielding hybrids for this region. Data collected on the performance of F1 and three-way hybrids from a total of 25 multi-environment trials (METs) located in South Africa (three trials), Zambia (four trials) and Zimbabwe (eighteen trials) grown across two seasons during the period from 2015–2018 to: (i) identify new single cross testers for CIMMYT HG-B maize germplasm; (ii) identify stable and high yielding three-way hybrids. Analyses were conducted using a two-stage approach. Clustering based on yield data, grouped sites into three environment types (ET); low (LY) < 3 t ha−1, medium (MY) 3–6 t ha−1 and high (HY) 6–13 t ha−1 yielding groups. Additive genetic effects of both inbred parents and selected F1 crosses used as parents were more important than non-additive genetic effects for grain yield across ETs. Strong genotype x environment interactions on yield and other traits were observed. It was concluded that F1 hybrids (entry 75, 85, 72 and 28) demonstrated high yield across all environment types, and it is recommended that these be also evaluated as potential three-way hybrids. Single crosses CZL15085/CML566 and CZL15085/CZL13102 from heterotic group B to be used as testers for ET 1 and ET 2 respectively.

Copyright of Journal of Natural & Agricultural Sciences / Revista de Ciencias Naturales & Agropecuarias is the property of ECORFAN-Mexico S.C. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Monitoring genetic gains within breeding programs is a critical component for continuous improvement. While several national breeding programs in Africa have assessed genetic gain using era studies, this study is the first to use two decades of historical data to estimate genetic trends within a national breeding program. The objective of this study was to assess genetic trends within the final two stages of Zimbabwe's Department of Research & Specialist Services maize breeding pipeline between 2002 and 2021. Data from 107 intermediate and 162 advanced variety trials, comprising of 716 and 398 entries, respectively, was analyzed. Trials were conducted under optimal, managed drought stress, low nitrogen stress, low pH, random stress, and disease pressure (maize streak virus (MSV), grey leaf spot (GLS), and turcicum leaf blight under artificial inoculation. There were positive and significant genetic gains for grain yield across management conditions (28-35 kg ha-1 yr-1), under high-yield potential environments (17-61 kg ha-1 yr-1), and under low-yield potential environments (0-16 kg ha-1 yr-1). No significant changes were observed in plant and ear height over the study period. Stalk and root lodging, as well as susceptibility to MSV and GLS, significantly decreased over the study period. New breeding technologies need to be incorporated into the program to further increase the rate of genetic gain in the maize breeding programs and to effectively meet future needs. [ABSTRACT FROM AUTHOR]

Site regression model (SREG) is utilized by plant breeders for the analysis of multi-environment trials (MET) to examine the relationships among test environments and genotypes (G) and genotype-by-environment interaction (GE). In its regular form, singular-value decomposition (SVD) is applied on residual matrix from one-way analysis of variance (ANOVA) to partition G plus GE effects. However, ANOVA and SVD are sensitive to atypical observations, which are common in MET. To overcome this problem, three robust models are proposed to obtain valid results even in the presence of outliers. Their efficacy was evaluated by simulation and compared with standard SREG. Different scenarios were considered to identify the appropriate strategies to deal with outliers in real situations. Two real datasets are also presented to highlight the usefulness of the proposed methods in agricultural data. Our results indicate that the use of the proposed alternatives enables to effectively analyze MET data in the presence of outliers and maintain good performance without them as well. [ABSTRACT FROM AUTHOR]

Genotype assessment across various environments is a basic condition for developing stable and superior genotypes for sustainable maize production in the South-East of the DR Congo. Therefore, this research’s objectives were to identify the performance of newly developed provitamin A maize genotypes in various environments, and to recommend high-performing and stable genotypes for broader adaptation. Eight provitamin A maize genotypes, including one commercial variety, were planted at three sites during two consecutive cropping seasons (2020/2021 and 2021/2022) forming six environments. All genotypes in six environments were planted in a randomized complete block design containing three replications. Two stability analysis approaches, GGE biplot and Eberhart and Russell method are widely used to identify high yielding and stable genotypes. The combined analysis of variance revealed that G and E as well as their interaction (GEI) have significantly affected the emergence rate, cob’s insertion height, days to anthesis and silking, cob length, cob grain weight and grain yield. Average grain yield varied from 8.30 t/ha for PVAH-7L to 9.41 t/ha for PVAH-1L. The Eberhart and Russell method and the CV identified PVAH-1L, PVAH-4L, PVAH-7L and PVAH-6L as the most stable genotypes, but could not reliably identify the high yielding genotypes. On the other hand, the GGE biplot reliably and graphically showed the stable and high-yielding genotypes (PVAH-1L > PVAH-6L) as well as the low-yielding genotypes (PVAH-7 > PVAH-4L). In additional, the GGE biplot showed that L’shi21 was the best test environment for selecting high performing and stable provitamin A maize genotype. The results of this study indicate that PVAH-1L and PVAH-6L are the stable, high-yielding provitamin A maize genotypes in the South-East of the Democratic Republic of the Congo and should be disseminated in this region. [ABSTRACT FROM AUTHOR]

The objective of this work was to evaluate the alterations of antioxidant enzyme reserves and antioxidant enzymes during germination under water deficit in maize hybrids and to associate with seed vigor, determining the mechanisms related to tolerance for this stress. Two three-way maize hybrids were characterized by their vigor at different levels of water deficit induced by polyethylene glycol 6000. Next, the seeds were hydrated at different osmotic potentials (0.0, -0.3, and -0.9 MPa) and removed at different times to assess the levels of the total soluble protein, total soluble sugars, proline, starch, and antioxidant enzymes, such as superoxide dismutase, catalase and ascorbate peroxidase. The analysis of variance, Tukey test at 5% and principal component analysis (PCA) were used. The vigorous hybrid (HT1) was more efficient than the low vigor hybrid seeds (HT2) in mobilizing the total soluble protein during the initial stages of germination and the total soluble sugars before and after root protrusion under water deficit in addition to increasing the catalase activity at the different osmotic potentials that were assessed.

Copyright of African Crop Science Journal is the property of African Crop Science Journal and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)