Three-way Cross Research Articles

Stability Analysis in Six-row Barley Genotypes for Grain Yield in Multi-environmental Trails Using Eberhart and Russel (1966)

The current study aimed to determine the phenotypic stability for grain yield per plant under three distinct environmental conditions using fifteen parental lines and three testers with 45 crosses (30 single crosses and 15 three-way crosses) of six-row barley in three replications using Randomized Block Design. Eberhart and Russell (1966) developed the modal to examine stability. The mean sum of squares due to genotype and environment wassquares due to genotype and environment were found to be significant for grain yield per plant, which showed the differential effect of environment on genotypes. For grain yield per plant, it was also observed that the mean sum square resulting from the climate + (G x E) interaction, E (linear), and G x E (linear) was significant. With a non-significant deviation from regression (S2di=0) and regression coefficient near unity (bi=1), the genotypes BG 959, BG 105 x RD 2508, PL 751 x RD 2508, DWRB 137 x RD 3005, and RD 2035 x F1 exhibited higher grain yield than the population mean. These genotypes were the most stable and desirable under variable environmental conditions. These genotypes could be used as donors in regular breeding programs to improve barley grain yield.

Combining ability of Egyptian cotton (Gossypium barbadense L.) reveals genetic potential for improved yield and fiber quality

BackgroundAs the most widely cultivated fiber crop, cotton production depends on hybridization to unlock the yield potential of current varieties. A deep understanding of genetic dissection is crucial for the cultivation of enhanced hybrid plants with desired traits, such as high yield and fine fiber quality. In this study, the general combining ability (GCA) and specific combining ability (SCA) of yield and fiber quality of nine cotton parents (six lines and three testers) and eighteen F1 crosses produced using a line × tester mating design were analyzed.ResultsThe results revealed significant effects of genotypes, parents, crosses, and interactions between parents and crosses for most of the studied traits. Moreover, the effects of both additive and non-additive gene actions played a notably significant role in the inheritance of most of the yield and fiber quality attributes. The F1 hybrids of (Giza 90 × Aust) × Giza 86, Uzbekistan 1 × Giza 97, and Giza 96 × Giza 97 demonstrated superior performance due to their favorable integration of high yield attributes and premium fiber quality characteristics. Path analysis revealed that lint yield has the highest positive direct effect on seed cotton yield, while lint percentage showed the highest negative direct effect on seed cotton yield. Principal component analysis identified specific parents and hybrids associated with higher cotton yield, fiber quality, and other agronomic traits.ConclusionThis study provides insights into identifying potential single- and three-way cross hybrids with superior cotton yield and fiber quality characteristics, laying a foundation for future research on improving fiber quality in cotton.

Development of novel egg type chicken variety with improved productivity for rural backyards of India

Rural poultry farming with improved high producing chicken varieties is transforming the rural livelihoods. The present study was aimed at developing a high egg producing variety suitable for backyard poultry farming. A total of 602 female birds representing five crossbreds, i.e. Kadaknath × IWH (KH), PD-3 × IWH (DH), PD-2 × IWH (VH), PD-1 × IWH (CH) and PD-3 × KH (DKH) were evaluated for their performance up to 72 weeks under farm conditions. The traits evaluated were body weights at 8, 16, 20, 40, 52, 64 and 72 weeks age at sexual maturity (ASM), egg production and egg weight at 40, 52, 64 and 72 weeks and egg quality traits. Analysis of variance was used to assess the effect of genotypes on different traits and heterosis was estimated to check the superiority of the crosses over the parent lines. Genotype had significant influence on all the traits. Morphologically, only DKH crossbred had multi-coloured plumage, while all other crosses had white plumage with brown patches. DKH cross produced about 239.2±2.96 eggs annually and also witnessed the highest heterotic gains for all the body weight traits. Also, heterosis for ASM was very low for DKH cross and hence, in desired direction. Based on present findings, the three-way DKH cross owing to its multi-coloured plumage and good performance can be further studied for its potential as a high-producing layer variety in rural backyards.

Genotype and phenotype diversity of the F2 population three-way cross soybean (Glycine max [L.] Merrill) results

Increasing soybean production through plant crossing helps to supply soybean needs. Three-way crossing of three parents, Grobogan, Anjasmoro, and Dega 1 is expected to increase soybean productivity. Interbreeding is an effort to form a basic population to increase genetic diversity. Based on this, this study aims to determine the diversity of genotypes and phenotypes of the F2 population resulting from a cross between three soybean parents [Glycine max (L.) Merrill]. This research was conducted on Tanjung Selamat Village, Sunggal District, Deli Serdang Regency land. Observations were made by observing all plant populations in the field. Characters observed include plant height, flowering age, number of primary branches, and harvest age. The results showed that the diversity of genotypes and phenotypes of the F2 population varied, this was based on the highest standard deviation value in the F2 population compared to the 3 parent soybean plants. The plant height character has a high diversity value based on the KKG and KKF values.

Increasing sunflower production in Uganda through seed importation and developing local sunflower hybrids

There is great potential for growing sunflower in Uganda. For the last decade, the farmers of Uganda have picked interest in the growing of sunflower. This is because of availability of ready market from the oil millers. However, production is constrained by limited available high yielding sunflower hybrids. Much of the seed is imported from International Seed Companies. Single cross hybrids and three-way cross hybrids were evaluated to check which types gives better yield, oil content and other desirable traits. Preliminary results showed that a number of three-way cross hybrids yielded better than the imported hybrids. We are therefore contemplating towards emphasis on scaling out three-way cross compared to single cross hybrids which is generally grown worldwide.

Heterosis from eucalypt single and multi-cross hybrids

Hybridizing is one of the most important ways to genetically improve eucalypts; especially to tropical species. Because of the high efficiency of asexual using hybrid heterosis, the current planting eucalypt varieties in most tropical areas in the world are hybrids. It’s well known that crossing different eucalypt species in different ways can create hybrids with different characters. But, it’s unclear what kind of species matings tend to create more heterosis. Here we systematically made and tested hybrids of: pure species by pure species (single cross), pure species by hybrids (three-way cross), hybrids by hybrids (double cross). The tropical eucalypt species we used as parents include: Eucalyptus urophylla, E. grandis, E. pellita, E. tereticornis and hybrids between them. The field testing results found: the overall performance of tree volume was: single cross > three way cross > intraspecies cross > double cross. Their 4-year advantages over intraspecies cross were: 29.9%, 8.0% and -12.5%. The coefficient of variation of the 4 types were: 55.3%, 61.2%, 64.0% and 67.1%. As for the survival rate, 4-year result was: double cross (72.6%) > three way cross (71.6%) > single cross (70.8%) > intraspecies cross (54.0%). This shows that the interspecies hybrids had similar environmental adaption, and they were all significantly higher than that of intraspecies cross. The single and multi-cross hybrids had similar coefficient of variation on survival rate. Combining with the results on family and individual tree level heterosis frequency and magnitude, we found that single-cross has more heterosis on volume growth while muti-cross has more heterosis on adaption. Genetic parameter analysis showed that single-cross hybrids have both high additive and high dominant heritability. But the heritability value on different species combinations can be very different. Three way-cross hybrids had the highest additive heritability, but very low dominant heritability. The double-cross hybrids had high dominant heritability, but very low additive heritability.

Skipping irrigation at pre- and post-anthesis stages influences grain yield and starch contents of bread wheat derived from synthetic or landraces

This study aims to evaluate the role of genetic diversity originated from three-way crosses of landraces and synthetic bread wheat derivatives attempted with elite cultivars to identify the genotypes having better grain yield as well as better starch contents under flowering stage drought stress. In total, 50 genotypes comprised of 47 derivatives of landraces and synthetics, and three standard varieties were grown in the fields of CIMMYT, Obregon following alpha lattice design with two replications. Drought stress was imposed by stopping the irrigation before anthesis and post-anthesis stages. Different traits related to physiological adaptations, earliness, grain yield and starch contents were decreased under drought stress except amylose which increased significantly. Canopy temperature depression was not significantly affected by drought stress. Further, we identified strong correlation of grain yield with plant height, normalized difference in vegetation index, plant maturity, spike length, grain number and thousand grain weight but negative with canopy temperature depression. Non-significant correlation of amylose and amylopectin was recorded with grain yield. Results revealed that genetic diversity derived from landraces and synthetic bread wheat can improve grain yield and starch contents but simultaneous improvement of both is elusive.

Performance of some Three-Way Cross Hybrids and Their Parents of Maize in the Middle Region of Iraq

There is increasingly demand of maize as a staple food in poultry industry in Iraq, where the average production of yield 4.5 tons, which is still faint as compared to neighbor countries. 30 of Three-Way Cross Hybrids of Maize along with five parental inbred lines were evaluated in four replications during the 2017 fall season at the research station of Agriculture College/Al-Jadrya, Baghdad to evaluate their performances and estimate the heterosis for grain yield (GY), and related traits. Most of the studied three-way cross hybrids out-yielded their parental inbred lines for the studied traits. TW8 and TW10 were identified as the excellent hybrids with average yield 219 and 214 gm/plant respectively with positive heterosis reached 72 and 62% respectively.

Development of inter-specific hybrids between Solanum melongena L. and Solanum sisymbriifolium Lam. through embryo rescue

In present investigation, inter-specific hybridization between two species was carried out using a three-way cross with the aim to study the response of heterotic hybrids for cross-compatibility and to improve the fertility traits of interspecific cross such as pollen viability and density for further introgression of agronomically important traits. The present investigation highlights genotypic variation of for cross-compatibility between S. melongena hybrids and Solanum sisymbriifolium. Among three hybrids, H3 x Solanum sisymbriifolium (4%) and H4 x Solanum sisymbriifolium (1.5%) showed compatibility for fruit set and developed immature seeds only. The embryo rescue from 25 day-old fruits and in vitro culture on ½ MS medium supplemented with 2mg/L–1BAP showed germination. H5 x S. sisymbriifolium showed 49.4% embryo germination and produced four complete plantlets. Furthermore, all plants were morphologically variable for the presence or absence of spines, flower clustering, slightly curved/straight stigma tip, and flower color. The regenerated plantlets were intermediate to cultivated and wild parents for the quantitative traits. Two SSR markers viz., emg01A17, emh11001 and emb01E03 also confirmed the hybridity of three-way cross plants. Among four interspecific plants, one established high pollen viability (78.5%), while others were partial-fertile (62.8%) and all carried low pollen density (69-299 pollen/ 1cm2) at anthesis. Inbreeding and backcrossing of these plants to both cultivated and wild parents remained unsuccessful. This is the first report of developing a partially-fertile three-way cross between S. melongena and S. sisymbrifollium via embryo rescue.

Comparison of Growth Performance and Plasma Metabolomics between Two Sire-Breeds of Pigs in China.

The Yorkshire pigs, renowned for their remarkable growth rate, low feed conversion ratio (FCR), and high meat production, emerge as a novel preference for paternal breeding. In this study, we found that purebred paternal Yorkshire pigs (PY) surpass the purebred Duroc breed in terms of growth rate. Specifically, purebred PY attain a weight of 100 kg at an earlier age compared to purebred Duroc (Male, 145.07 vs. 162.91; Female, 145.91 vs. 167.57; p-value < 0.01). Furthermore, different hybrid combinations suggest that offspring involving purebred PY exhibit superior growth performance. Compared with purebred Duroc, the offspring of purebred PY have an earlier age in days (173.23 vs. 183.54; p-value < 0.05) at the same slaughter weight. The changes of plasma metabolites of 60-day-old purebred boars in the two sire-breeds showed that 1335 metabolites in plasma were detected. Compared with Duroc, 28 metabolites were down-regulated and 49 metabolites were up-regulated in PY. Principal component analysis (PCA) discerned notable dissimilarities in plasma metabolites between the two sire-breeds of pigs. The levels of glycerol 3-phosphate choline, cytidine, guanine, and arachidonic acid increased significantly (p-value < 0.05), exerting an impact on their growth and development. According to our results, PY could be a new paternal option as a terminal sire in three-way cross system.

ASSEMBLY OF SOYBEAN GENOTYPES DEVELOPED THROUGH THREE-WAY CROSS

A three-way cross is an artificial cross performed to assemble superior cultivars for increased soybean production. The presented study aims to evaluate the percentage of success in the single cross and three-way cross of soybean genotypes to enhance the genetic variability in the base population of the genetic material. The genetic material comprises three soybean cultivars, i.e., Grobogan, Anjasmoro, and Dega-1. The three-way cross design operation made various crosses. Parameters observed were plant morphology, percentage of cross success and seed formation in pods, number of seeds in pod, and the total seed weight. The results showed a relatively high (57.14%) success rate for the cross Grobogan × Anjasmoro, producing numerous one-seeded and two-seeded pods and 30 seeds per plant with a total weight of 5.4 g. However, the success rate in three-way cross (F1 descent [Grobogan × Anjasmoro] × Dega-1) was medium (35.37%). The results of crossing the three genotypes of parents will greatly determine soybean variability.

The phenotype of the three-way cross soybean (Glycine max [L.] merrill) results

The high demand for soybeans can be met by increasing soybean production through crossbreeding. Crossbreeding of soybean varieties using the three-way cross method from three parents, namely Grobogan, Anjasmoro, and Dega 1, can be a solution to the problem. Increasing genetic diversity through cross breeding is one of the efforts to form a primary population. Therefore, this study aimed to determine the agronomic character of the F1.1 generation of soybean plants resulting from a cross between three parents. This study was carried out in a land located in Emplasmen Kwala Mencirim Village, Sei Bingai District, Langkat Regency. The observations were carried out by observing all the plants planted in the field. This study showed that the height of the F1.1 plants resulted from a cross of three parents varied, and the mean number of primary branches produced was 2.72. The mean seed weight of the F1.1 is 17.62 g.

GENETIC CHARACTERISTICS OF F2 POPULATIONS OBTAINED THROUGH DOUBLE AND THREE-WAY CROSSES IN CAYENNE PEPPERS

The enhancement in cayenne pepper (Capsicum frutescens L.) productivity is intently needed due to the ever-increasing demand, considered a vital vegetable commodity with complete nutrition and high economic value in Indonesia. Conventional plant breeding is one of the strategies to produce superior cultivars with increased yield. Thus, the latest research aimed to identify genetic diversity and gene inheritance patterns for selecting high-yielding F2 populations of cayenne pepper made through double and three-way crosses. The said research employed an augmented design combined with a randomized complete block design as an environmental design. The research factors consisted of non-repeating cayenne pepper (Capsicum frutescens L.) lines with a limited number of seeds originating from 10 parental populations. The resulting 100 and 52 F22 individual populations, obtained from double and three-way crosses, respectively, were evaluated in comparison with four control cultivars, i.e., Bara, Dewata, Ungara, and Katokkon. The non-repeated rows, divided into five blocks, included the control cultivars planted repeatedly in each block. The results indicated that almost all traits have high genetic diversity and heritability and have potential use as selection criteria. The traits plant habitus (0.135), stem diameter (0.202), number of productive branches (0.359), and fruit weight (0.171) have a direct utmost influence on yield compared with other traits; thus, these promising traits can serve as selection criteria along with yield.

Performances of three-way cross hybrids over their respective single crosses and related heterosis of maize (Zea mays L.) hybrids evaluated in Ethiopia

Less attention had been given to the performances of three-way crosses and its comparative advantages of these hybrids over single crosses. This study was carried out to evaluate the performances of three-way crosses in comparison to single crosses for yield and related agronomic traits and to estimate the magnitude of heterosis. The trial was laid out in a simple alpha lattice design of 10 × 6 for lines, 6 × 5 for single crosses (SC), and 9 × 5 for three way-crosses and planted in adjacent plots in the 2019 cropping season in three locations namely Ambo, Abala-Farcha and Melkassa. Single cross hybrids showed a highly significant (P<1%) variation for grain yield, plant height, ear height, and ear length at three locations. These single cross hybrids had showed also a highly significant genotype by environment interaction (P < 1%) for grain yield, plant height, ear height and kernel per ear. Regarding three-way crosses, there was a significant variation (P<5%) on grain yield in Ambo and Melkassa but on ear height and rows per ear in Abala-Faracho. The genotype × environment interaction was significantly varied for grain yield, ear height and ear length. In the comparison, 80% crosses in Ambo, 73% in Abala-Faracho and 67% in Melkassa showed that three-way crosses were better in their performance than that of their respective single crosses. On the other hand, the single crosses that out-performed their respective three-way crosses were higher in Melkassa than Abala-Faracho and the least were reported from Ambo. Similarly, the maximum better and mid-parent heterosis was from single cross 1(769%) in Ambo and single cross 7 (104%) in Melkassa whereas TWC 14 (52%) and TWC 24 (78%) were the highest better and mid-parent heterosis, respectively in Ambo, TWC1 (56%), and TWC30 (25%) were the highest BPH, and MPH, respectively in Melkassa.

Mapping a leaf rust resistance gene LrOft in durum wheat Ofanto and its suppressor SuLrOft in common wheat.

Epidemics of leaf rust (caused by the fungal pathogen Puccinia triticina Erikss., Pt) raise concerns regarding sustainability of wheat production. Deployment of resistant cultivars is the most effective and economic strategy for combating this disease. Ofanto is a durum wheat cultivar that exhibits high resistance to Pt race PHT throughout its entire growing period. In the present study, we identified a leaf rust resistance gene in Ofanto and temporarily designated it as LrOft. LrOft was mapped to a 2.5 cM genetic interval in chromosome arm 6BL between Indel markers 6B6941 and 6B50L24. During introgression of LrOft from Ofanto to common wheat it was observed that F1 plants of Ofanto crossed with Shi4185 exhibited leaf rust resistance whereas the F1 of Ofanto crossed with ND4503 was susceptible. In order to map the presumed suppressor locus, a Shi4185/ND4503//Ofanto three-way pentaploid population was generated and SuLrOft was mapped on chromosome arm 2AS. SuLrOft was mapped within a 2.6 cM genetic interval flanked by 2AS50L14 and 2AS50L6. Fine mapping using 2,268 plants of the three-way cross narrowed the suppressor locus to a 68.2-kbp physical interval according to IWGSC RefSeq v1.1. Sequence analysis of genes in the physical interval revealed that TraesCS2A02G110800 encoding an RPP-13-like protein with an NB-ARC domain was a potential candidate for SuLrOft.

Individualizing treatment choices for patients with type 2 diabetes according to patient preference

Many patients with Type 2 diabetes will require additional glucose lowering treatment to achieve optimal glucose control. Ensuring treatment adherence is therefore crucial in order to reduce the long-term risks of complications. A study recently published in Nature Medicine, known as the TriMaster study is the first study to evaluate the effectiveness of allowing people with type 2 diabetes to choose their own second/third line medication to manage hyperglycaemia. This approach was thought to balance the potential efficacy with potential side effects profiles of the selected drugs. The study led by academics from the University of Exeter was a randomized double-blind, three-way cross over trial where patients received three different second- or third-line once-daily type 2 diabetes glucose-lowering drugs (pioglitazone 30 mg, sitagliptin 100 mg and canagliflozin 100 mg). As part of a prespecified secondary endpoint, patients' drug preference were examined after they had tried all three drugs. In total, 448 participants were treated with all three drugs which overall showed similar glucose lowering outcomes. In terms of preference, 115 patients (25%) preferred pioglitazone, 158 patients (35%) sitagliptin and 175 patients (38%) canagliflozin. The drug preferred by individual patients was associated with a lower HbA1c (mean: 4.6; 95% CI: 3.9, 5.3) mmol mol−1 lower versus nonpreferred) and was associated with fewer side effects (mean: 0.50; 95% CI: 0.35, 0.64) fewer side effects versus nonpreferred). This study showed that allocating therapy based on patients individually preferred drugs, rather than allocating all patients the overall most preferred drug (canagliflozin), would result in more patients achieving the lowest HbA1c for them (70% versus 30%) and the fewest side effects (67% versus 50%). Given the comparable glucose lowering ability of different drugs, allowing patients to try suitable medications before they choose long-term therapy according to their treatment preference could be a practical alternative to individualised treatment strategy for type 2 diabetes that would facilitate long-term treatment compliance.

Predicting the impact of genotype-by-genotype interaction on the purebred–crossbred genetic correlation from phenotype and genotype marker data of parental lines

BackgroundThe genetic correlation between purebred (PB) and crossbred (CB) performances ({r}_{pc}) partially determines the response in CB when selection is on PB performance in the parental lines. An earlier study has derived expressions for an upper and lower bound of {r}_{pc}, using the variance components of the parental purebred lines, including e.g. the additive genetic variance in the sire line for the trait expressed in one of the dam lines. How to estimate these variance components is not obvious, because animals from one parental line do not have phenotypes for the trait expressed in the other line. Thus, the aim of this study was to propose and compare three methods for approximating the required variance components. The first two methods are based on (co)variances of genomic estimated breeding values (GEBV) in the line of interest, either accounting for shrinkage (VCGEBV-S) or not (VCGEBV). The third method uses restricted maximum likelihood (REML) estimates directly from univariate and bivariate analyses (VCREML) by ignoring that the variance components should refer to the line of interest, rather than to the line in which the trait is expressed. We validated these methods by comparing the resulting predicted bounds of {r}_{pc} with the {r}_{pc} estimated from PB and CB data for five traits in a three-way cross in pigs.ResultsWith both VCGEBV and VCREML, the estimated {r}_{pc} (plus or minus one standard error) was between the upper and lower bounds in 14 out of 15 cases. However, the range between the bounds was much smaller with VCREML (0.15–0.22) than with VCGEBV (0.44–0.57). With VCGEBV-S, the estimated {r}_{pc} was between the upper and lower bounds in only six out of 15 cases, with the bounds ranging from 0.21 to 0.44.ConclusionsWe conclude that using REML estimates of variance components within and between parental lines to predict the bounds of {r}_{pc} resulted in better predictions than methods based on GEBV. Thus, we recommend that the studies that estimate {r}_{pc} with genotype data also report estimated genetic variance components within and between the parental lines.

Gut microbial diversity among Yorkshire, Landrace and Duroc boars and its impact on semen quality

The gut microbiota plays an important role in pig health and performance, particularly in host growth and fecundity. In present study, the characteristics and diversity of gut microbiota in fine purebred boars from three-way crossbred “Duroc×Landrace×Yorkshire” pigs were investigated using 16 S rRNA gene sequencing. The results showed that the three breeds of boars shared similar gut microbiota, yet there remain slight differences at the family/genus level. At the family level, Ruminococcaceae, Streptococcaceae and Lactobacillaceae have the highest abundance in Landrace, while Rikenellaceae and f_p_251_o5 have the highest abundance in Duroc. The abundance of Prevotellaceae, Lachnospiraceae and Spirochaetaceae in intestinal of Yorkshire were higher than that of Landrace and Duroc. In addition, ten and six biomarkers were identified in the microbiota across breeds and months of age, respectively. Moreover, we evaluated the effect of gut microbiota on boar semen quality, revealing that Duroc had the strongest sperm vitality, significantly associated with the genus Rikenellaceae_PC9_gut_group. In addition, the spermatogenesis ability and sperm production improved gradually along with increase of age. In conclusion, this study provides a reference for understanding the gut microbiota composition of purebred boars used for three-way crosses and their impact on semen performance.

Genome-wide association and transcriptome studies reveal the segregation mechanism of mantle markings in three-way cross hybrid abalone

Trait separation which often appears in shellfish progeny, has been commercially used in shellfish breeding projects. A three-way cross hybrid abalone was produced with heterosis in growth performance and thermal tolerance, and with segregation in mantle marking. However, the inheritance mechanism of mantle marking is unclear. In this study, mantle marking was demonstrated to be a qualitative trait, following simple Mendelian inheritance, through inheritance pattern analysis of the presence of black markings on the mantle in five families of three-way cross of hybrid abalone. Thermal tolerance of abalone was assessed by the Arrhenius breakpoint temperature (ABT) of cardiac performance and a correlation between mantle marking and thermal tolerance of abalone was verified. A genome-wide association study (GWAS) for mantle marking was conducted using 603,067 high-quality single nucleotide polymorphisms (SNPs) derived from 57 individuals with mantle markings (Y group) and 58 individuals without mantle markings (N group). A total of 493 SNPs that were significantly (p &amp;lt; 2.32E–07) associated with mantle markings were mainly distributed on chromosome 15. In the potential significantly associated region, 80 genes, including pigmentation-related genes PTPRT, PTPRC, PNCA, and CALM4 were annotated. Transcriptome analysis of the two groups showed that the expression levels of these genes (PTPRT, DDT-b, ATOX1, SLC6A3, and GSTO1) were significantly different, and they may play important roles in the formation of mantle markings in the three-way cross hybrid abalone. Overall, our data provide valuable information for deciphering the phenotype differences of mantle marking in three-way cross hybrid abalone and help in the molecular marker-assisted breeding in abalone.

Genetic Potential of New Maize Inbred Lines in Single-Cross Hybrid Combinations under Low-Nitrogen Stress and Optimal Conditions

Maize (Zea mays, L.) productivity in sub-Saharan Africa (SSA) remains low, despite breeding efforts spanning across decades. Currently, three-way cross hybrids (TWCH) dominate SSA; however, there is the potential to increase yields by using single-cross hybrids. In this study, five new and four elite CIMMYT lines were inter-mated in a half diallel mating scheme to estimate the combining ability of the lines and to determine the stability of their corresponding 36 single-cross hybrids for grain yield under low-nitrogen stress and optimum growing conditions in Zimbabwe and Zambia. The results revealed that the new inbred line CL121290 showed the highest GCA effects under optimum conditions (1.4 tha−1; p &lt; 0.001) and across sites (0.93 tha−1; p &lt; 0.001). The single-cross hybrids G12 (CML311 × DJL173527) and G16 (DJL173887 × CL1211559) were highly stable and were observed as ideal crosses within both the low-nitrogen and optimal environments. However, G18 (CML311 × DJL173887), which was depicted as ideal genotype under the two management conditions, was an unstable genotype. Hybrid G31 (CML311 × CML312) had the least grain yield under low-nitrogen, optimum and across environments. The hybrid G11 (DJL173527 × CL121290) was the highest yielding genotype amongst the new single-cross hybrids and across environments but was unstable and can be recommended for high potential in environments. Overall, the data demonstrated the potential of single-cross hybrids to supplement TWCH in boosting maize productivity under optimal and nitrogen-stress environments in SSA as well as under other areas with similar climatic conditions in the world.