Assessment of Genotype by Environment interactions and Grain Yield Performance of Extra-Early Maize (Zea Mays L.) Hybrids

Maize (Zea mays L.) is one of the most important cereal crops of Ghana in terms of production and consumption. Currently, it is produced in all the agro-ecological zones of the country. In Ghana, Genotype by Environment interactions (GxE) effects on maize grain yield is usually significant due to the diverse environmental conditions at growing sites. A proper understanding of the effects of GxE on variety evaluation and cultivar recommendations is vital. The study was conducted in 2011 at three locations in Ghana to (i) determine the presence of GxE of 100 extra-early maize genotypes and (ii) To use the GGE biplot methodology to determine grain yield performance and stability of the genotypes evaluated across three environments. The effects of genotype and environment were significant (P < 0.01) for grain yield. However, GxE was not significant for the same trait. TZEEI 8 x TZEEI 51, TZEEI 5 x TZEEI 53, TZEEI 21 x TZEEI 39, TZEEI 27 x TZEEI 36 and TZEEI 4 x TZEEI 6 were identified as high yielding and most stable hybrids. Therefore, these hybrids have the potential for production across the test locations as well as others within the same agro-ecological zones. On the contrary, DODZI, TZEEI 23 x TZEEI 6, TZEEI 19 x TZEEI 24, TZEEI 11 x TZEEI 24 and TZEEI 20 x TZEEI 39 were not only low yielding but also among the least stable genotypes. Keywords: Zea mays, single-cross, stability, multiple environments, Gx

Gains in genetic enhancement of early maturing maize hybrids developed during three breeding periods under striga-infested and striga-free environments

Open Access Journal; Published online: 13 Aug 2020Striga hermonthica is a major maize production constraint in West and Central Africa (WCA). Fifty-four early maturing maize hybrids of three breeding periods: 2008–2011, 2012–2013, 2014–2015, were evaluated under Striga-infested and non-infested environments in WCA. The study aimed at assessing genetic improvement in grain yield of the hybrids, identifying traits associated with yield gain during the breeding periods, and grain yield and stability of the hybrids in Striga infested and non-infested environments. Annual increase in grain yield of 101 kg ha−1 (4.82 %) and 61 kg ha−1 (1.24%) were recorded in Striga-infested and non-infested environments, respectively. The gains in grain yield from period 1 to period 3 under Striga-infested environments were associated with reduced anthesis-silking interval, reduced Striga damage, number of emerged Striga plants, improved ear aspect, and increased ears per plant. Ear aspect, ears per plant, and Striga damage at 8 and 10 weeks after planting (WAP) were significantly correlated with yield in Striga-infested environments, whereas ears per plant and plant and ear aspects had significant correlations with yield in non-infested environments. Hybrids TZdEI 352 × TZEI 355, TZdEI 378 × TZdEI 173, and TZdEI 173 × TZdEI 352 were outstanding in grain yield and stability in Striga-infested environments, whereas TZEI 326 × TZdEI 352, TZEI 495 × ENT 13, and TZdEI 268 × TZdEI 131 were superior in non-stress environments. These hybrids should be further tested extensively and commercialized. Significant genetic gains have been made in breeding for resistance to Striga hermonthica in early maturing maize hybrids

Combining ability of extra-early maize inbreds derived from a cross between maize and Zea diploperennis and hybrid performance under contrasting environments

Open Access JournalKnowledge of the genetic mechanisms conditioning drought tolerance in maize is crucial to the success of hybrid breeding programs aimed at developing high-yielding cultivars under drought. The objectives of this study were to determine the combining ability of extra-early inbreds, compute the heritability of measured traits, assess the performance of inbreds in hybrid combinations and investigate the associations among traits under drought and optimal conditions. A total of 252 hybrids generated by crossing 63 inbreds to four testers, along with four commercial hybrid checks, were evaluated for 2 years under drought and rainfed conditions. General combining ability (GCA) and specific combining ability (SCA) for the traits were significant. A total of 57.1% and 53.4% of the genotypic sum of squares were attributable to GCA effects for grain yield under managed drought and rainfed conditions, respectively. Hybrids TZdEEI 91 × TZEEI 21 and TZdEEI 55 × TZEEI 13 out-yielded the best checks under drought and optimal conditions by 49.13% and 39.05%, respectively. The most promising hybrids with consistently high grain yield under drought and rainfed conditions, were TZdEEI 54 × TZEEI 13, TZdEEI 91 × TZEEI 21 and TZdEEI 55 × TZEEI 21 and should be further evaluated for possible commercial production in sub-Saharan Africa

Enhancing genetic gains in grain yield and efficiency of testing sites of early-maturing maize hybrids under contrasting environments

The major challenges of maize production and productivity in Sub-Saharan Africa (SSA) include Striga hermonthica infestation, recurrent drought, and low soil nitrogen (low N). This study assessed the following: (i) accelerated genetic advancements in grain yield and other measured traits of early-maturing maize hybrids, (ii) ideal test environments for selecting early-maturing multiple-stress tolerant hybrids, and (iii) high-yielding and stable hybrids across multiple-stress and non-stress environments. Fifty-four hybrids developed during three periods of genetic enhancement (2008–2010, 2011–2013, and 2014–2016) were evaluated in Nigeria, The Republic of Benin, and Ghana under multiple stressors (Striga infestation, managed drought, and Low N) and non-stress environments from 2017 to 2019. Under multiple-stress and non-stress environments, annual genetic gains from selection in grain yield of 84.72 kg ha−1 (4.05%) and 61 kg ha−1 (1.56%), respectively, were recorded. Three mega-environments were identified across 14 stress environments. Abuja was identified as an ideal test environment for selecting superior hybrids. The hybrid TZdEI 352 × TZEI 355 developed during period 3 was the most outstanding under multiple-stress and non-stress environments. On-farm testing of this hybrid is required to verify its superior performance for commercialization in SSA. Considerable progress has been made in the genetic improvement of early-maturing maize hybrids for tolerance of multiple stressors and high yield. The identified core testing sites of this study could be used to enhance the testing and selection of promising hybrids

Genetic diversity and population structure of early-maturing tropical maize inbred lines using SNP markers

Open Access Journal; Published online: 9 April 2019Information on genetic diversity and population structure are very important in any breeding programme for the improvement of traits of interest and the development of outstanding products for commercialization. In the present study, we assessed the genetic diversity of 94 early-maturing white and yellow tropical maize inbred lines using single nucleotide polymorphism (SNP) markers. The larger number of SNP markers used in this study allowed a clearer inference of the population structure of the 94 inbred lines. Cluster analysis resolved the inbred lines into different clusters based on their pedigree, selection history and endosperm colour. However, three heterotic groups were revealed by population structure analysis, but additional field evaluation could be more informative to confirm the heterotic groups identified. Nevertheless, wide genetic variability existed among the inbred lines making them unique with the potential to contribute new beneficial alleles to maize breeding programmes in the tropics, especially in the West and Central Africa (WCA) sub-region

Genetic enhancement of early and extra-early maturing maize for tolerance to low-soil nitrogen in sub-Saharan Africa

Open Access ArticleTo increase and improve food crop production and crop management for sustainable agricultural development, the Maize Improvement Program (MIP) of the International Institute of Tropical Agriculture (IITA) has, in partnership with national and international organizations, focused attention on the genetic improvement of maize (Zea mays L.) for tolerance/resistance to abiotic and biotic stresses constraining maize grain production. One of the abiotic stresses into which new technologies have been established for crop protection and sustainable natural resource management is low soil nitrogen (N). Nitrogen, an important plant nutrient required for growth and productivity, is not readily available and little quantity or none is applied by farmers for maize production. Because of long periods of bush fallow, the absence of N was not noticeable at the initial stages of maize production in West and Central Africa (WCA). However, with the fallow period gradually reducing and totally disappearing, it has become imperative for external supply of N in maize production. Taking a cue from the International Maize and Wheat Improvement Centre (CIMMYT), IITA has been breeding low-N tolerant maize and several low-N-tolerant maize varieties and hybrids are now available to farmers. Reviewed in this manuscript are the efforts used to develop low-N tolerant early and extra-early maturing maize by the MIP of IITA. The review covers the objectives, methodology, and output of the research, including the genetics of tolerance, ongoing conventional and molecular approaches, and the gaps that new research could fill

Trait profile of maize varieties preferred by farmers and value chain actors in northern Ghana

Open Access Article; Published online: 06 Jul 2021Plant breeders’ knowledge of precise traits preferred by variety users would accelerate varietal turnover and widen adoption of newly developed maize varieties in Ghana. The objective of this research was to provide empirical evidence of trait preferences of farmers and other actors in the maize value chain in northern Ghana, based on which research strategies for maize improvement could be formulated. Participatory rural appraisal was conducted in 2016 to determine key traits preferred by maize value chain actors across the three regions in northern Ghana. A total of 279 maize value chain actors were interviewed. Different scoring and ranking techniques were used to assess the maize traits preferred by the different actors. Participatory variety selection trials were also conducted in the Tolon, West Gonja, Binduri, and Sissala East districts in northern Ghana from 2014 to 2016. The mother-baby trial approach was used to evaluate eight hybrids with 3000 farmers. Data on yield and agronomic performance of the hybrids and farmer’s selection criteria were collected. Data analyses were performed using GenStat Edition 16 and SPSS Edition 20 statistical packages. The participatory rural appraisal method identified farmers, input dealers, traders, and processors as the primary maize value chain actors in the study areas. Trait preferences of the different actors overlapped and revolved around grain quality including nutritional value, and stress tolerance and grain yield. Results of the participatory variety selection study revealed that across districts, farmers preferred high-yielding varieties with multiple cobs per plant, white grain endosperm color, and bigger and fully filled cobs. For the first time, our holistic assessment of the trait preferences of key actors of the maize value chain in northern Ghana revealed a comprehensive list of traits, which could be used by breeders to develop varieties that may be preferred by all value chain actors in northern Ghana

Estimating genetic gains for tolerance to stress combinations in tropical maize hybrids

Open Access Journal; Published online: 08 Dec 2022Maize is a strategic food crop in sub-Saharan Africa. However, most maize growing tropical savannas particularly in West and Central African experience the occurrence of frequent droughts and Striga infestation, resulting in 30–100% yield losses. This production zones need maize cultivars that combine tolerance to the two stresses. IITA in collaboration with national partners has thus employed a sequential selection scheme to incorporate both drought tolerance and Striga resistance in topical maize hybrids using reliable screening protocols. The main objective of the present study was therefore to use grain yield and other agronomic traits recorded in regional collaborative hybrid trials conducted for 8 years under manged stressful and non-stressful conditions and across rainfed field environments to estimate genetic gains in grain yields using mixed model analyses. The results showed significant (p < 0.05) annual yield gains of 11.89 kg ha−1 under manged drought stress (MDS) and 86.60 kg ha−1 under Striga infestation (STRIN) with concomitant yield increases of 62.65 kg ha−1 under full irrigation (WW), 102.44 kg ha−1 under Striga non-infested (STRNO) conditions and 53.11 kg ha−1 across rainfed field environments. Grain yield displayed significant but not strong genetic correlation of 0.41 ± 0.07 between MDS and STRIN, indicating that gene expression was not consistent across the two stress conditions. Furthermore, grain yield recorded in MET had significant moderate genetic correlations of 0.58 ± 0.06 and 0.44 ± 0.07It with MDS and STRIN, respectively. These results emphasize the need to screen inbred linens under both stress conditions to further enhance the rate of genetic gain in grain yield in hybrids for areas where the two stresses co-occur. Nonetheless, this study demonstrated that the sequential selection scheme has been successful in generating hybrids with dependable yields that can reduce chronic food deficits in rural communities experiencing simultaneous presence of drought and S. hermonthica infestation in their production fields

Consistent patterns of common species across tropical tree communities

Trees structure the Earth’s most biodiverse ecosystem, tropical forests. The vast number of tree species presents a formidable challenge to understanding these forests, including their response to environmental change, as very little is known about most tropical tree species. A focus on the common species may circumvent this challenge. Here we investigate abundance patterns of common tree species using inventory data on 1,003,805 trees with trunk diameters of at least 10 cm across 1,568 locations1,2,3,4,5,6 in closed-canopy, structurally intact old-growth tropical forests in Africa, Amazonia and Southeast Asia. We estimate that 2.2%, 2.2% and 2.3% of species comprise 50% of the tropical trees in these regions, respectively. Extrapolating across all closed-canopy tropical forests, we estimate that just 1,053 species comprise half of Earth’s 800 billion tropical trees with trunk diameters of at least 10 cm. Despite differing biogeographic, climatic and anthropogenic histories7, we find notably consistent patterns of common species and species abundance distributions across the continents. This suggests that fundamental mechanisms of tree community assembly may apply to all tropical forests. Resampling analyses show that the most common species are likely to belong to a manageable list of known species, enabling targeted efforts to understand their ecology. Although they do not detract from the importance of rare species, our results open new opportunities to understand the world’s most diverse forests, including modelling their response to environmental change, by focusing on the common species that constitute the majority of their trees

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries