Quality Protein Maize Hybrids Research Articles

Genetic Evaluation of Heterosis and Combining Ability of Quality Protein Maize (Zea mays L.) Hybrids under Terminal Heat Stress Conditions

Background: The development of quality protein maize (QPM) hybrids tolerant to terminal stress environments has been an essential strategy for reducing the associated loss in grain yield. A study by Badu-Apraku et al., (2019) employed line × tester analysis in QPM breeding, highlighting its efficacy in selecting QPM hybrids. While QPM varieties resistant to disease, drought and environmental stresses have been developed conventionally, the adoption of improved QPM genotypes in farmers’ field is restricted mainly due to lack of proper team effort among maize breeders, farmers, agricultural extension workers and other relevant stakeholders. Methods: In line × tester mating design, six lines and three testers were crossed under heat stress environment and 18 F1s along with parental lines were evaluated along with check varietal during summer season, 2023, P.G research farm, CUTM, Paralakhemudi, Odisha. The objective of the current study was to evaluate parental lines and its crosses based on combining ability and heterosis. Result: ANOVA revealed significant to revealed significant differences for all the traits between parents, lines, testers and lines vs testers, except for cob height, chlorophyll content and canopy temperature. 𝛔2GCA/𝛔2SCA values for parents/hybrids recorded lower than unity for all the trait studied suggesting preponderance of non-additive gene action. Parental lines CML149, CML143 and CML330 are the best general combiners for early flowering, grain yield per plant and antioxidant status. Among eighteen crosses, two hybrids CML149 × CML330 and CML143 × CML193 recorded significant SCA effects for early flowering, grain yield per plant and antioxidant levels. Hybrids CML149 × CML330 (33.31%) and CML143 × CML193 (28.31%) noted significant standard heterosis for grain yield per plant over commercial check, HQPM-1. Hybrids CML149 × CML330 and CML143 × CML193 were resilient to terminal heat stress as they didn’t exhibit signs of leaf firing, tassel blast, root lodging and loss of yield.

Hybrid performance and grain yield stability for advanced provitamin A and quality protein maize hybrids evaluated in Ethiopia

Hybrid performance and grain yield stability for advanced provitamin A and quality protein maize hybrids evaluated in Ethiopia

Testcross performance and combining ability of early-medium maturing quality protein maize inbred lines in Eastern and Southern Africa

Limited commercial quality protein maize (QPM) varieties with low grain yield potential are currently grown in Eastern and Southern Africa (ESA). This study was conducted to (i) assess the performance of single-cross QPM hybrids that were developed from elite inbred lines using line-by-tester mating design and (ii) estimate the general (GCA) and specific (SCA) combining ability of the QPM inbred lines for grain yield, agronomic and protein quality traits. One hundred and six testcrosses and four checks were evaluated across six environments in ESA during 2015 and 2016. Significant variations (P ≤ 0.01) were observed among environments, genotypes and genotype by environment interaction (GEI) for most traits evaluated. Hybrids H80 and H104 were the highest-yielding, most desirable, and stable QPM hybrids. Combining ability analysis showed both additive and non-additive gene effects to be important in the inheritance of grain yield. Additive effects were more important for agronomic and protein quality traits. Inbred lines L19 and L20 depicted desirable GCA effects for grain yield. Various other inbred lines with favorable GCA effects for agronomic traits, endosperm modification, and protein quality traits were identified. These inbred lines could be utilized for breeding desirable QPM cultivars. The QPM hybrids identified in this study could be commercialized after on-farm verification to replace the low-yielding QPM hybrids grown in ESA.

Genotype × environment interaction and grain yield stability of quality protein maize hybrids under stress and non-stress environments

Genotype × environment interaction and grain yield stability of quality protein maize hybrids under stress and non-stress environments

Selection of extra-early white quality protein maize (Zea mays L.) inbred lines for drought and low soil nitrogen resilient hybrid production

In West and Central Africa (WCA), drought and low soil nitrogen (low N) impede increased maize (Zea mays L.) productivity and production. Due to climate change, the two stresses usually occur together, leading to food, nutritional, and economic insecurity in the sub-region. There is, therefore, the need for the development and availability of high-yielding extra-early maturing white Quality Protein Maize (QPM) synthetics and hybrids with resilience to the prevailing stresses through the identification of superior climate smart (extra-early maturing) QPM inbreds under stress (drought and low soil N) conditions. The study was conducted to identify stress-resilient QPM inbred lines for hybrid production and assess the association between grain yield and other studied characters. During the 2012 minor and major rainy seasons, 96 extra-early white QPM inbreds and four (4) normal endosperm maize inbred checks were assessed in multi-location trials under stress and optimal conditions in Nigeria. The experiments were laid out in a 10 × 10 simple lattice design with two replications. Data were recorded on grain yield and other agronomic traits. Significant variations (p < 0.01) were detected among the inbred lines for measured characters, indicating adequate genetic variability among the inbreds to allow for selection and improvement of grain yield and other measured traits. Grain yield was interrelated with all the traits used in the selection index. Moderate to high estimates of heritability were observed for most of the measured traits under stress conditions, indicating that the traits could be easily transmitted to the progenies. Fifty-seven out of the 96 QPM inbreds evaluated exhibited varying degrees of resilience to drought and low N. The QPM inbreds with desired traits may be used as genetic resources for the incorporation of tolerance genes into QPM populations in the tropics, as well as for the development of drought and low N resilient synthetics and hybrids in WCA.

Heterosis of quality protein maize inbred lines for agronomic traits and association with genetic distances based on SSR and phenotypic markers

Due to high cost, limited labour, and longer time required in hybrid development, identifying promising hybrids at an early stage without large-scale yield trials is crucial. Therefore this study estimated heterosis of quality protein maize hybrids for grain yield (GY) and other agronomic traits and investigated relationship of genetic and phenotypic distances (GD, PD) of inbreds with hybrid performance (HP) and mid-and-better parent heterosis (MPH, BPH). Forty-five hybrids generated by half-diallel with 10 inbreds were evaluated for GY and other agronomic traits at three locations. The yield trials were conducted for two years (2017 and 2018 cropping seasons). The GD and PD were 0.45 and 0.40 based on SSR and phenotypic data, respectively, this shows moderate genetic variation existed among inbreds. GY had highest MPH (77.55%) and BPH (53.96%) with hybrid TZEEQI-9 × TZEEQI-16 having highest MPH (382.8%) and BPH (331.7%), across locations. Positive and significant association existed between SSR-GD with HP, MPH and BPH for ear length, kernels/row and 100-seed weight (r = 0.31** to 0.41**), this suggests these traits can be predicted from SSR-based GD of parents. These traits could be used for indirect selection for yield improvement. However, negative correlation was obtained between SSR-GD with HP, MPH and BPH for anthesis and silking (r = −0.29 to −0.03), this indicates the dominance for earliness to flowering and silking than their parental lines. The two distance measures can be used to differentiate between maize inbreds and assigned them to different heterotic groups and Breeders can therefore prioritize crosses with high heterosis and desirable phenotypic traits, saving time, resources, and field space.

The combining ability of extra-early maturing quality protein maize (Zea mays) inbred lines and the performance of their hybrids in Striga-infested and low-nitrogen environments

Maize production in sub-Saharan Africa (SSA) faces challenges due to the damage caused by the parasitic weed, Striga hermonthica (Del.) Benths and low soil nitrogen. To address these constraints and improve food security and nutrition, this study assessed the combining ability of 47 inbred lines and four testers, grouped them into heterotic groups, identified effective testers, and determined the stability of the lines in hybrid combinations under contrasting research conditions. The study was conducted at Mokwa and Abuja during the 2019 and 2020 growing seasons. One hundred and ninety-six hybrids comprising 188 testcrosses, 6 hybrids derived by intermating the four testers, and two commercial checks were evaluated using a 14 × 14 lattice design with two replicates. Results revealed that under Striga infestation, the best quality protein maize (QPM) hybrid, TZEEQI 468 × TZEEQI 321, outyielded the best check, TZEEQI 342 × TZEEQI 7, by 24%. Under low-N, QPM hybrid, TZEEQI 515 × TZEEQI 321 outyielded the best check, TZEEQI 507 × TZEEQI 7 by 11% while under optimal conditions the best QPM hybrid, TZEEQI 506 × TZEEQI 321 outyielded the best check, TZEEQI 342 × TZEEQI 7 by 2%. General combining ability (GCA) and specific combining ability (SCA) significantly influenced grain yield and other measured traits across the test environments. These indicated the importance of both additive and non-additive genetic variances in trait inheritance. GCA was more important than SCA for grain yield and most traits in contrasting environments. Four inbred lines had significant and positive GCA effects for grain yield under Striga-infested conditions, while three lines had similar GCA effects under low-nitrogen conditions. These lines demonstrated outstanding potential for developing Striga-resistant and low-nitrogen-tolerant hybrids. The study identified four heterotic groups using the heterotic grouping method based on the general combining ability of multiple traits (HGCMAT). Inbred lines TZEEQI 490 and TZEEQI 460 were identified as testers. The QPM hybrid TZEEQI 515 × TZEEQI 321 exhibited outstanding yield and stability across contrasting environments, highlighting the need for extensive on-farm trials to confirm its superiority and potential for commercialization in SSA.

Performance and Yield Stability of Quality Protein Maize (Zea mays L.) Hybrids under Rainfed Condition

Abstract Quality protein maize (QPM) commercialization can combat the food and nutritional insecurity that is common in some developing nations of the world. Evaluation of QPM hybrids under varying rainfed environments provide valuable evidence for the selection of the most productive genotypes for the target environment. The present study was conducted at three locations to assess the agronomic performance and the grain yield stability of 11 QPM and 2 commercial hybrids (checks) over two years. There were significant (p ≥ 0.01) differences among the environments in the expression of all measured traits while genotype as well as genotype × environment interaction also differed significantly for all the traits except for husk cover and Anthesis-silking interval. The tested QPM hybrids outperformed the local and reference checks by 17.28% and 29.47% respectively. The biplot explained 85.3% of the total variation in yield, with 65.4% attributed to principal component 1 and 19.9% to principal component 2. Three vertex hybrids, EWQH-25, EWQH-21 and Local Check, were identified as the most responsive in the environments within which they fall. Hybrid EWQH-21 produced the highest yield across all environments but was unstable. Therefore, hybrids EWQH-22, EWQH-9, and EWQH-13, with similar yield values and more stable performances were recognized as ideal across environments. Lapai 2017 (E2) proves to be both representative and discriminative, making it the ideal test environment for selecting hybrids with broad adaptability. The study concludes that EWQH-9, EWQH-13, and EWQH-22 be recommended for cultivation across the environments while EWQH-21 be recommended for the specific area of adaptation.

Predicting zinc‐enhanced maize hybrid performance under stress conditions

AbstractThe low yield potential of most biofortified maize is a barrier to its full adoption and reduces its potential to curb various macro‐ and micronutrient deficiencies highly prevalent in low‐income regions of the world, such as sub‐Saharan Africa (SSA). By crossing biofortified inbred lines with different nutritional attributes such as zinc (Zn), provitamin A and protein quality, breeders are attempting to develop agronomically superior and stable multi‐nutrient maize of different genetic backgrounds. A key question, however, is the relationship between the biofortified inbred lines per se and hybrid performance under stress and non‐stress conditions. In this study, inbred line per se and testcross performance were evaluated for grain yield and secondary traits of Zn‐enhanced normal, provitamin A and quality protein maize (QPM) hybrids and estimated heterosis under combined heat and drought (HMDS) and well‐watered (WW) conditions. Responses of all secondary traits, except for the number of days to mid‐anthesis, significantly differed for HMDS and WW conditions. The contribution of heterosis to grain yield was highly significant under both management levels, although higher mid and high‐parent heterosis was observed under WW than HMDS conditions. However, the findings suggest that inbred line performance was the best determinant of hybrid performance under HMDS. Strong correlations were observed between grain yield and secondary traits for both parents and hybrids, and between secondary traits of inbred lines and hybrids under both management levels, indicating that hybrid performance can be predicted based on intrinsic inbred line performance. Phenotypic correlation between grain yield of inbred lines and hybrids was higher under HMDS than WW conditions. This study demonstrated that under HMDS conditions, performance of Zn‐enhanced hybrids could be predicted based on the performance of their corresponding inbred lines. However, the parental inbred lines should be systematically selected for desirable secondary traits correlated with HMDS tolerance during inbred line development.

Effect of nutrient management and plant density on productivity of QPM hybrids of maize (Zea mays)

A field experiment was conducted during the rany season of 2014 and 2015 at the Rajasthan College of Agriculture, Maharana Pratap University of Agriculture and Technology, Udaipur, Rajasthan to study the effect of nutrient-management approaches on the performance of quality protein maize hybrids at varying plant densities. The results showed that ‘HQPM 1’ produced significantly higher yield attributes and yield over Pratap QPM hybrid– 1. Significantly higher yield parameters of QPM hybrids were observed in normal density (60 cm × 20 cm) over high density (50 cm × 20 cm) however, the yield was significantly higher with high density than the normal density. Nutrient application through soil-test-crop response (STCR) approach resulted in significantly higher yield parameters and yield over site-specific nutrient management (SSNM), recommended dose of fertilizers (RDF) and green seeker approaches during both the years. Thus, growing of ‘HQPM 1’ with 1,00,000 plants/ha and STCR approach followed by SSNM approach may be adopted for higher yield.

Improvement in nutritional quality of traditional unleavened flat bread using Quality Protein Maize.

Maize grains are consumed majorly in the form of unleavened flat bread (chapatti) in the South East Asian region. The landraces are better accepted for their chapatti-making attributes such as grain color and good organoleptic properties. However, these cultivars are low in essential amino acids, particularly lysine and tryptophan content. Hence, an investigation was performed to identify maize genotypes with high nutritional value coupled with good chapatti-making qualities. Seven genotypes, comprising two Quality Protein Maize (QPM) hybrids, two normal maize hybrids, and three normal white maize landraces were assessed for their physical characteristics, proximate composition, and chapatti-making quality. Landrace 593 showed the highest protein and ash content. Flours obtained from different genotypes were significantly different (p ≤ 0.001) in terms of protein content, color value, textural, as well as mineral content. PMH 10 and IQMH 203 exhibited the highest and lowest hydration index, respectively. Two QPM hybrids showed significantly higher lysine and tryptophan content as compared to other genotypes. QPM hybrids were identified as the promising material with improved nutritional quality with respect to chapatti making. In combination with mustard greens, maize chapatti constitutes an important traditional delicacy in north India. The enhanced nutritional quality of QPM chapattis is an added advantage. We show the differentiation of chapattis made from QPM and normal maize using a rapid protocol developed previously. This is expected to enable the development and quality control of commercial enterprises based on high protein quality QPM.

Breeding quality protein maize (Zea mays): Genetic and analytical perspective

Maize is one of the prominent cereal crops locally as well as internationally for both biological and industrial processing. The nutritional value of maize grains is graded to be poor due to limiting essential amino acids mainly lysine and tryptophan. A series of events beginning by the discovery of the opaque-2 mutation until the development of enhanced protein quality cultivars paved the way for the role of amino acid modifiers genes and proteins. Quality Protein Maize (QPM) is the improved variant of the normal maize with enhanced protein quality. Protein body (PB) formation and the association of the molecular structure of the starch and PB has been a study of concern. Various changes in biochemical pathways leading to the changed zein and non-zein proportions have been studied using transgenic technology which forms an important component of maize protein. Maintaining the quality parameter of QPM inbreds, hybrids and populations so developed is a scientific concern to the speedy and precise determination of quality parameters and further maintaining these parameters using standard breeding methods. The role of biochemist and biochemical techniques are of great significance in maize quality protein research since high throughput and precise nutrient profiling of breeding lines, populations, inbred lines and hybrids support a sound QPM development programme. Various advanced techniques have been developed so far, for the protein isolation till detection and quantification of protein.Among these, the most advanced is the Ultra Performance Liquid Chromatography(UPLC) technique which is highly accurate and can be used efficiently for amino acid profiling of the maize germplasm, breeding lines and hybrids to support the decision making the process in QPM breeding programme. Thus, this review gives us an overview of the breeding methods and biochemical techniques utilized in the development of QPM in the current year 2019 and beyond.

Stability Analysis of Quality Protein Maize Hybrids Qualitative and Quantitative Traits under Heat Stress across Different Environments of Prayagraj District in Central India

Maize, also known as corn (Zea mays .L), is one of the world's most important cereal crops. Maize is the only food cereal crop that can be produced throughout the year and requires a moderate environment to thrive. This study claims to determine whether such a statement is accurate and to examine stability in terms of gene action. The study was carried out in three research sites representative different places in CRF, SHUATS, Prayagraj City at an elevation of 98 meters above sea level at 25.87ON latitude and 81.54 OE longitude. and all the locations has sub-tropical climate with extremes of summer and winter. During winter season especially in month of December and January, temperature drops down to as low as 1-20 C, while during summer the temperature reaches up to 450C (NICMEIT 2022). This experiment was undertaken under Randomized Block Design with three replications for assessing their stability. The mean squares due to genotypes, parents, hybrids, and parent vs. hybrids were very significant for all eighteen quantitative and qualitative characters under study, according to the analysis of variance for diallel analysis (model I method II). A stability study was carried out to determine the grain yield of 45 maize hybrids under three environments (E1, E2 and E3), using Eberhart and Russel model. The analysis of variance for combining ability revealed the mean squares due to general combing ability (GCA) and specific combing ability (SCA) were highly significant for all characters studied. Inbred lines P4, P5 and P2 showed significant to highly significant positive GCA effects on grain yield per plant and its attributes, indicating that both parents were good general combiners for this trait. Four hybrids (P5 X P7, P5 X P6, P4 X P8 and P4 X P5) exhibited significant to highly significant SCA effects for grain yield per plant. The estimates of standard heterosis over the best check (HQPM-5) for grain yield per plant revealed five top cross combinations (P5 X P7, P5 X P6, P4 X P8, P5 X P9 and P4 X P5), exhibiting highly significant positive standard heterosis regarding their high and stable performance across environments. The single cross hybrids over all the environments P5 X P6, P5 X P7 and P4 X P5 were found promising for the majority of characters studied, with high mean performance across environments. Based on a regression coefficient close to unity (βi ≈1) and a non-significant deviation from regression (s2di), indicating their adaptability across all environments investigated, best performing hybrids were identified according to three different environments in E1, E2 and E3 were P1 X P6, P2 X P4, P2 X P6, P2 X P8, P3 X P5, P4 X P5, P4 X P7, P4 X P10, P5 X P6, P5 X P7, P6 X P8, P7 X P8, P7 X P9, regression coefficient near to unity (βi ≈1) and non-significant deviation from regression (s2di) there by indicating its adaptability over all environments, thus indicating stable performance in different environments for most of the characters.

Grain quality and yield potential of hybrids from quality and non-quality protein maize inbred lines

Identification of maize hybrids with enhanced quality trait(s) is important for addressing malnutrition among the increasing human population. The objective of this study was to assess quality trait performance of quality protein maize (QPM) and non-QPM lines crossed with QPM and non-QPM testers. A total of 130 hybrid progenies (48 QPM x QPM, 64 QPM x non-QPM and 18 non-QPM x non-QPM) were generated from QPM and non-QPM lines and testers. Two QPM and three non-QPM checks were included and these 135 hybrids were evaluated in field experiments across six locations. The QPM x QPM hybrid group had a protein quality index (QI) and tryptophan content value of 0.99 and 0.078 respectively, compared to the 0.55 and 0.048, and 0.5 and 0.045, of the QPM x non-QPM and non-QPM x non-QPM group, respectively. This indicated a loss of the tryptophan and QI advantage caused by the opaque2 gene in QPM in the QPM x non-QPM crosses. Therefore, to retain nutritional value, QPM should not be allowed to cross with non-QPM maize. The average protein content of the QPM x QPM group (7.9%) was significantly lower than that of the QPM x non-QPM (8.74%) and non-QPM x non-QPM groups (9.03%). Some QPM hybrids did have excellent yield and nutritional value and can be promoted for commercial release.

Standard Heterosis Estimation for Quality Protein Maize Hybrids Over Best Released and Commercialized Hybrids

Maize plays an indispensable role in meeting high food demand. It is globally one of the most widely adopted and cultivated crops. Hybrid development from fixed inbred lines is one of the tactics to boost maize production. The national average maize yield in Ethiopia is low and thus, selection of promising germplasm, knowledge of combining ability, and heterotic grouping are prerequisites to develop high-yielding maize varieties. Forty-two Quality Protein Maize (QPM) single crosses (21 inbred lines each crossed with two testers) along with three popular standard hybrid checks were evaluated in two replications using alpha lattice design during the 2017 cropping season at Ambo, Arsi-Negele, and Kulumsa. The objective of this study was to estimate standard heterosis for grain yield (GY), and other agronomic and morphological characters. Significant difference among crosses was observed for 19 traits at Ambo, 14 traits at Arsi-Negele, and 19 traits at Kulumsa in the hybrid trial. For GY, at Ambo, almost all crosses showed negative heterosis against the best check (AMH853). At Arsi-Negele 14 crosses had positive standard heterosis, from these only three crosses: L8xT1 (50.8%), L8xT2 (46.6%), and L7xT1 (33.9%) showed significant difference against Jibat but at Kulumsa, the difference for standard heterosis was positive but non-significant only by two crosses: (L7xT1 (6.6%) and L19xT1 (4.7%). Based on mean grain yield and standard heterosis, L8xT2, L7xT1, L8xT1, L19xT1, L6xT2, and L18xT1 are promising. The study of the results highlighted that the breeding program was successful in generating superior QPM hybrids. Based on the finding we suggest that it is better to use the parents of theses hybrids as potential source materials in the breeding program through to form different crosses formation.

Genetic analysis of maize genotypes possessing novel combination of opaque2 and opaque16 genes affecting higher accumulation of lysine and tryptophan in kernels

Traditional maize protein is nutritionally poor due to low levels of lysine (0.150–0.250%) and tryptophan (0.030–0.040%). The recessive opaque2 (o2) gene that enhances lysine (0.300–0.400%) and tryptophan (0.070–0.100%) is used in developing quality protein maize hybrids. Mutant opaque16 (o16) in the presence of o2 further enhances lysine and tryptophan. Here we analyzed a set of seven diverse maize inbreds possessing o2 and o16 for their potential to develop heterotic hybrids. Characterization of inbreds using 75 SSRs revealed 177 alleles with wide variation in dissimilarity coefficient (0.34–0.80). Phylogenetic analysis grouped the o2o2/o16o16-based inbreds into three clusters. Inbreds were further crossed in a half-diallel mating design, resulting in 21 experimental hybrids were evaluated at two locations. Experimental o2o2/o16o16-based hybrids possessed significantly higher lysine (0.506%) and tryptophan (0.126%) compared to commercial o2-based QPM hybrids (lysine: 0.346%, tryptophan: 0.086%). Combining ability for grain yield identified several promising inbreds and hybrids. Grain yield was significantly correlated with genetic distance (r = 0.57**) and SCA effect (r = 0.67**). Selected hybrids with >7500 kg/ha grain yield, >0.500% lysine and >0.120% tryptophan possess great potential in providing both food- and nutritional-security. The improved hybrids with a novel combination of o2 and o16 provide sustainable and cost-effective solution to alleviate protein energy malnutrition.

Performance Evaluation and Identification of Highland Quality Protein Maize Hybrids in Ethiopia

Background: Maize plays an indispensable role in meeting high food demand. It is globally one of the most widely adopted and cultivated crops. Hybrid development from fixed inbred lines is one of the strategies for the improvement of maize production. The national average maize yield is low in East Africa; thus, the selection of promising germplasm has a great role to meet the high food demand of growing the population. Forty-two Quality Protein Maize (QPM) crosses (21 inbred lines each crossed with two testers) along with three popular standard hybrids checks were evaluated in two replications using alpha lattice during the 2017 cropping season at Ambo, Arsi-Negele, and Kulumsa. The objective of this study was to evaluate and select the best new QPM hybrids for grain yield, and other agronomic and morphological characteristics.
 Results: Significant difference among crosses was observed for 19 traits at Ambo, 14 traits at Arsi-Negele, and 19 traits at Kulumsa. Out of 28 traits studied, six of them did not show genotype by location interaction but they showed a significant genotypic effect. These traits were: Days to Silking (DS), Number of Ears per plant (EPP), Ear Length (EL), Kernels Per Row (KPR), Ear Diameter (ED), and Thousand Seed Weight (TSW). Based on the mean performance in the combined analysis, from 42 new QPM crosse, six of them (L8xT2, L7xT1, L8xT1, L19xT1, L6xT2, and L18xT1) were scored higher grain yield compared with the mean of the three standard checks and best conventional maize (CM) check (AMH853). L8xT2, L7xT1, L8xT1 crosses showed a higher grain yield advantage over the best check (AMH853) by 20.87, 14.13, and 13.63%, respectively.
 Conclusion: The study implicated the existence of a difference between the newly developed hybrids and the standard check varieties. In general, the study enabled us to identify promising crosses that could be forwarded for further use in maize breeding programs in future work.

Mid-parent and Better Parent Heterosis Study on Highland Quality Protein Maize Hybrids in Ethiopia

Determination of heterosis in maize hybrids is necessary for the identification of superior F1 hybrids for breeding programs. Therefore, this study was conducted to estimate the amount of mid parent (MPH) and better parent heterosis (BPH) for grain yield, yield-related, agronomic, and morphological traits. Hybrid development from fixed inbred lines is one of the strategies for the improvement of maize production. The national average maize yield in Ethiopia is low and thus, selection of promising germplasm, knowledge of combining ability, and heterotic grouping are prerequisites to developing high-yielding maize varieties. Forty-two Quality Protein Maize (QPM) crosses (21 inbred lines each crossed with two testers) along with three popular standard hybrids were evaluated in two replications using alpha lattice during the 2017 cropping season at Ambo and, Arsi-Negele. Parental line trials consisting of 21 lines, two testers, and one conventional maize (CM) parent check (FS67) were established in two replications laid out using RCBD side by side with the hybrid trials at Ambo and Arsi-Negele. At Ambo, almost all crosses showed positive and significant BPH except three crosses (L1xT1, L4xT1, and L13xT1). The maximum BPH (276.2%) was obtained from L17xT2. Similarly, at Arsi-Negele, most of the crosses had positive and significant BPH except for five crosses for BPH which are showing negative heterosis. The highest BPH was obtained from L10xT2 at Arsi-Negele. Generally, the high yielding crosses had reasonable BPH. Based on the result promising crosses and lines were identified. Some of the crosses showed good performance in terms of heterosis against the mid parent and better parent: L17xT2 (329.88% MPH, 276.18% BPH), L3xT2(320.05% MPH, 273.91%BPH), and L19xT2(2802.57% MPH, 247.31% BPH) at Ambo, whereas at Arsi-Negele L10xT2 (128.38% MPH, 111.27%BPH) and L11xT2(115.33% MPH, 98.00% BPH) showed the higher heterosis compared with the mid parent and better parent. Crosses that showed best yield performance were: L8xT2, L7xT1, L8xT1, L19xT1, L6xT2, and L18xT1. These crosses should be reconsidered for further evaluation and possible release.

Genotype–genotype × environment (GGE) biplot analysis of extra-early maturing quality protein maize hybrids for grain yield

Genotype–genotype × environment (GGE) biplot analysis of extra-early maturing quality protein maize hybrids for grain yield

Heritability and Associations among Grain Yield and Quality Traits in Quality Protein Maize (QPM) and Non-QPM Hybrids.

Maize (Zea mays L.) is the main staple cereal food crop cultivated in southern Africa. Interactions between grain yield and biochemical traits can be useful to plant breeders in making informed decisions on the traits to be considered in breeding programs for high grain yield and enhanced quality. The objectives of this study were to estimate the heritability of grain yield and its related traits, as well as quality traits, and determine the association between quality protein maize (QPM) with non-QPM crosses. Grain yield, and agronomic and quality trait data were obtained from 13 field trials in two countries, for two consecutive seasons. Significant genotypic and phenotypic correlations were recorded for grain yield with protein content (rG = 0.38; rP = 0.25), and tryptophan with oil content (rG = 0.58; rP = 0.25), and negative rG and rP correlations were found for protein with tryptophan content and grain yield with tryptophan content. Path analysis identified ear aspect, ears per plant, and starch as the major traits contributing to grain yield. It is recommended that ear aspect should be considered a key secondary trait in breeding for QPM hybrids. The negative association between grain yield and tryptophan, and between protein and tryptophan, will make it difficult to develop hybrids with high grain yield and high tryptophan content. Hence, it is recommended that gene pyramiding should be considered for these traits.