Single Cross Maize Hybrids Research Articles

Performance of Single Cross Maize Hybrids for Summer Planting in Western Nepal

In addition to being a major source of food, feed, and fodder, maize is one of the important cereals for the livelihood of hill farmers in Nepal. Low maize productivity in the western hills of Nepal has traditionally been associated with the absence of high yielding varieties. The purpose of this study was to find single cross maize hybrids that would be highly productive and adaptable for summer planting in western hills of Nepal. An alpha lattice design with three replications was used to evaluate one hundred single cross hybrids, including checks at NMRP, Rampur; DoAR, Surkhet; and DoAR, Doti during the summer season of 2019. In the evaluated maize hybrids, all measured traits showed significant genetic variation, indicating the presence of substantial genetic diversity among tested hybrids and significant genotype by environmental interaction highlighting the variable performance across locations. RML-145/RL-105, RML-97-1/RML-98, RML-145/RML-146, RML-138/RML-2, and RML-97-2/RL-105 was among the top 17 hybrids with grain yields of 8-9 t ha1. Significant correlations of grain yield with plant height, ear height, test weight, cob length, and cob diameter suggest that these are the important traits while selecting the hybrids for yield. The study also employed 20 SSR markers to explore genetic diversity of 25 inbred lines which were used for developing top yielding hybrids, grouped these inbred lines into five distinct cluster showed moderate genetic diversity, and higher yield performance of hybrids associated with diverse background of parental lines. The genotype by environment interactions highlights the importance of multilocation testing to ensure consistent or location specific performance across varied conditions. The results suggest the possibility of exploring high yielding, adaptive, and location specific hybrids that can help to enhance maize productivity of western Nepal and narrow down the yield gap.

Elucidating the genetic potential of hybrids derived from elite maize (Zea mays L.) inbreds for economic traits under North-Western Himalayan condition

Abstract This study was conducted to evaluate the combining ability of newly acquired maize inbred lines over the environments. Twenty-eight crosses developed by crossing eight elite inbreds in a half-diallel mating design were evaluated during kharif, 2019 for 12 agro-morphological traits in RBD with two replications at two different environments reflecting diverse agro-climatic and ecological conditions of North-Western Himalayas (SAREC, Kangra and HAREC, Bajaura). Analysis of variance showed that there was sufficient amount of genetic variability in the material studied. In accordance to Bartlett’s test, error variance was homogeneous only for six traits. Estimates of σ2SCA were higher as compared to σ2GCA both within and across environments for all the traits, except days to 75 per cent brown husk at Kangra, representing prevalence of non-additive gene action for these traits. The inbred line B73 at Bajaura, and LM14 at Kangra were found to be good general combiner for most traits. The inbreds with good GCA can be used as potential parents for the development of high yielding single cross maize hybrids. The hybrid combinations namely, B73 × BAJIM1811 and BAJIM1522 × BAJIM1811 were identified as potentially superior ones at Kangra and Bajaura environments. The identified promising hybrids need further assessment for their superiority in performance across the locations and over years. Keywords: General combining ability, specific combining ability, gene action and maize.

Evaluation of the Performance of Single Cross Maize Hybrids and Their Parents in the Spring and Autumn Seasons

Evaluation of the Performance of Single Cross Maize Hybrids and Their Parents in the Spring and Autumn Seasons

Seasonal Occurrence of Fall Armyworm (Spodoptera frugiperda J.E. Smith) in Maize: The Role of Sowing Dates

Fall armyworm is a destructive insect pest in maize farming and has expanded widely throughout various agroecological zones, which threatens food security. An experiment was carried out at the Winter Nursery (ICAR-IIMR, Hyderabad) field to study the occurrence of fall armyworm on maize single cross hybrid DHM 117 across different sowing dates during kharif and rabi seasons of 2021-22. Weekly observations were made on a whole-plot basis to record the number of plants damaged, the number of larvae, and egg masses per plant. Among the six sowing dates, the crop sown on 2nd August 2021, had a relatively lower mean percent of infestation range (4.02% - 80.37%), a minimum larval count per plant range (0.01 - 0.24), and the least number of egg masses per plant range (0.00 - 0.11). The findings will be helpful in the construction of forecasting models, facilitating the formulation of eco-friendly management tactics to manage fall armyworms in maize.

Genomic prediction in multi-environment trials in maize using statistical and machine learning methods

In the context of multi-environment trials (MET), genomic prediction is proposed as a tool that allows the prediction of the phenotype of single cross hybrids that were not tested in field trials. This approach saves time and costs compared to traditional breeding methods. Thus, this study aimed to evaluate the genomic prediction of single cross maize hybrids not tested in MET, grain yield and female flowering time. We also aimed to propose an application of machine learning methodologies in MET in the prediction of hybrids and compare their performance with Genomic best linear unbiased prediction (GBLUP) with non-additive effects. Our results highlight that both methodologies are efficient and can be used in maize breeding programs to accurately predict the performance of hybrids in specific environments. The best methodology is case-dependent, specifically, to explore the potential of GBLUP, it is important to perform accurate modeling of the variance components to optimize the prediction of new hybrids. On the other hand, machine learning methodologies can capture non-additive effects without making any assumptions at the outset of the model. Overall, predicting the performance of new hybrids that were not evaluated in any field trials was more challenging than predicting hybrids in sparse test designs.

Genomic prediction of yield performance among single-cross maize hybrids using a partial diallel cross design

Genomic prediction (GP) in plant breeding has the potential to predict and identify the best-performing hybrids based on the genotypes of their parental lines. In a GP experiment, 34 elite inbred lines were selected to make 285 single-cross hybrids in a partial-diallel cross design. These lines represented a mini-core collection of Chinese maize germplasm and comprised 18 inbred lines from the Stiff Stalk heterotic group and 16 inbred lines from the Non-Stiff Stalk heterotic group. The parents were genotyped by sequencing and the 285 hybrids were phenotyped for nine yield and yield-related traits at two locations in the summer sowing area (SUS) and three locations in the spring sowing area (SPS) in the main maize-producing regions of China. Multiple GP models were employed to assess the accuracy of trait prediction in the hybrids. By ten-fold cross-validation, the prediction accuracies of yield performance of the hybrids estimated by the genomic best linear unbiased prediction (GBLUP) model in SUS and SPS were 0.51 and 0.46, respectively. The prediction accuracies of the remaining yield-related traits estimated with GBLUP ranged from 0.49 to 0.86 and from 0.53 to 0.89 in SUS and SPS, respectively. When additive, dominance, epistasis effects, genotype-by-environment interaction, and multi-trait effects were incorporated into the prediction model, the prediction accuracy of hybrid yield performance was improved. The ratio of training to testing population and size of training population optimal for yield prediction were determined. Multiple prediction models can improve prediction accuracy in hybrid breeding.

Changes in grain-filling characteristics of single-cross maize hybrids released in China from 1964 to 2014

Grain filling is the determined physiological process for the yield obtainment of cereal crops. The grain filling characteristics of 50 maize brand hybrids released from 1964 to 2014 in China were assayed across multi-environments. We found that the grain filling duration (54.46%) and rate (43.40%) at the effective grain filling phase greatly contributed to the final performance of hundred-kernel weight (HKW). Meanwhile, along with the significant increase in hundred-kernel weight (HKW), the accumulated growing degree days (GDDs) for actual grain filling period duration (AFPD) for the selected brand hybrids released between 1960s to 2010s in China had a decadal increase of 23.41°C d. However, there was a decadal increase of only 19.76°C d for GDDs of the days from sowing to physiological maturity (DPM), which was also demonstrated by the continuous decrease in the ratio between the days from sowing to silking (DS) and DPM (i.e., from 53.24% in 1960s to 49.78% in the 2010s). However, there were no significant changes in grain filling rate along with the release years of selected hybrids. Moreover, the stability of grain filling characteristics across environments also significantly increased along with the hybrid released years. We also found that the exotic hybrids showed the longer grain filling duration at the effective grain filling phase and more stability of grain filling characteristics than those of Chinese local hybrids. According to the results of this study, it was speculated that the relatively longer grain filling duration, shorter DS, the higher grain filling rate, and steady grain filling characteristics would contribute to yield improvement of maize hybrids in the future.

Inbreeding and Genetic Erosion from a Finite Model of a Synthetic Formed with Single Crosses.

When a seed produced by a single-cross (SC) maize hybrid is sown, the resulting grain yield is usually lower than that of the hybrid due to the inbreeding generated. However, if a seed from a mixture of s hybrids were sown instead, the synthetic variety thus formed (SynSC) would have a lower inbreeding coefficient (FSynSC) and a higher grain yield. The grain yield s, the finite number of representatives of each parent SC (m) and the inbreeding coefficient of the parent lines of the SCs (F) are related to the FSynSC. In addition, randomness and the finite size of m can cause the loss of genes and genotypes and increase the FSynSC. The objectives of this study were to derive formulas for (1) expressing FSynSC in terms of m, F, and s, and (2) calculating the probability of the occurrence of gene and genotype loss. It was found that for the probability of no genotype being missing from the progeny representing a parent to be at least 0.95, it is necessary that m ≥ 15. It was also found that a sample size of 7 is sufficient for FSynSC to stabilize, more visibly as F is larger, and for the probability of the occurrence of erosion to be practically zero.

Estimates of Combining Ability and Association among Morpho-Agronomic Traits of Single Cross Maize (Zea mays L.) Hybrids

Screening genotypes have a crucial role to increase the efficiency of selections in plant breeding program. Therefore, this study was emphasized to determine combining ability and the association between traits among themselves and yield. The experiment was conducted at Haramaya University Research Station (Raare) for two years (2018 and 2019) using 4x7 alpha-lattice design with three replications. Pooled analysis of variance revealed highly significant (p≤0.01) variations among crosses for grain yield and related traits. According to the result of combining ability analysis, parental line L3 was identified as a good general combiner for grain yield, ear diameter, 1000-kernel weight, and days to maturity. Similarly; L1, L2, and L8 proved as the best general combiner for number of kernels per row. Crosses L1×L6, L3×L5, L4×L6, L4×L8, and L5×L7 were found good specific combiners for 1000-kernel weight. Furthermore, the cross L5×L6 was the best specific combiner for ear diameter, whereas L4×L7 for both number of kernels per row and 1000-kernel weight. Likewise, the crosses L1×L5, L3×L8, L6×L7, and L7×L8 were identified as the best specific combiner towards earliness. Moreover, thousand kernel weight showed significant positive correlation with grain yield, conversely, days to anthesis, days to silking, ear aspect, and Puccinia sorghi exhibited significant negative correlation with grain yield at genotypic and phenotypic levels. Ear length, 1000-kernel weight, number of kernel rows per ear, and Turcicum leaf blight had positive direct effect on grain yield at genotypic and phenotypic level. In general, the result presented in the study might be useful for further breeding process to improve the productivity of maize.

Evaluation of single cross maize hybrids during the spring season in Khairahani, Chitwan, Nepal

The experiment was conducted at Khairahani-5, Chitwan, Nepal from 28th February to 20th June 2021. Twenty single cross maize hybrids were evaluated for quantitative and qualitative traits. The experiment was conducted in a randomized complete block design (RCBD) with three replications. Data were recorded on flowering traits, physiological and disease traits, agro-morphological traits, and yield and yield contributing traits. Analysis of variance showed significant differences in all traits except for root lodging, the number of plants per hectare, leaf senescence, and plant aspect. The result indicated that HGABS2-15-2-1B/RL174 had the shortest days to anthesis and silking. The genotype RML138/RML140 was found to have double cob. The longest cob was found in RML76/RML146 (17.3 cm), while the highest cob diameter was found in the Shrestha (5.1cm). The maximum number of grains per row was obtained from RML57/RL174, while the highest thousand-grain weight was obtained in RAMPUR HYBRID-10. Shrestha variety produced highest grain yield (9.954tha-1) followed by RML191/RML18 (9.41tha-1), CAH1715 (9.356tha-1) and RML4/RL111 (9.021tha-1). The traits with the highest broad-sense heritability were the number of rows per ear (79%), days to fifty percent silking (75%), days to fifty percent anthesis (72%), thousand-grain weight (70%), and grain yield (68%). Correlation studies suggested that the number of ears per hectare, cob length, and thousand-grain weight showed a positive and significant correlation with grain yield. Therefore, RML191/RML18, CAH1715, and RML4/RL111 showed better performance in terms of grain yield.

Genomic insights into historical improvement of heterotic groups during modern hybrid maize breeding.

Single-cross maize hybrids display superior heterosis and are produced from crossing two parental inbred lines belonging to genetically different heterotic groups. Here we assembled 1,604 historically utilized maize inbred lines belonging to various female heterotic groups (FHGs) and male heterotic groups (MHGs), and conducted phenotyping and genomic sequencing analyses. We found that the FHGs and MHGs have undergone both convergent and divergent changes for different sets of agronomic traits. Using genome-wide selection scans and association analyses, we identified a large number of candidate genes that contributed to the improvement of agronomic traits of the FHGs and MHGs. Moreover, we observed increased genetic differentiation between the FHGs and MHGs across the breeding eras, and we found a positive correlation between increasing heterozygosity levels in the differentiated genes and heterosis in hybrids. Furthermore, we validated the function of two selected genes and a differentiated gene. This study provides insights into the genomic basis of modern hybrid maize breeding.

Agronomic Evaluations of Single Cross Maize (Zea mays L.) Hybrids under Zone 3 of Karnataka

Agronomic Evaluations of Single Cross Maize (Zea mays L.) Hybrids under Zone 3 of Karnataka

Genotype X Environment Interaction Studies in Single Cross Maize Hybrids for Quality Traits under Different Environments

Sixty eight genotypes of maize (48 hybrids, 16 parents and 4 checks were evaluated under three different environments to test their stability. Variance due to genotypes, environments and genotype x environment interactions were found significant for oil content, starch content and protein content. Regression approach by Eberhart and Russel 1966 used to investigate the nature of G x E interaction and for identifying genotypes possessing general and specific adaption. None of the hybrids had stability for all quality traits. For Grain Starch content hybrid EI-1155-1 x EI-2416, for oil content hybrid EI-670-2 x EI-2403 and for Protein content hybrids EI-2187 x EI-2403, EI-536-3 x EI-2403, EI-2176 x EI-561-2,EI-2173 x EI561-7 had higher mean values, non significant deviation from regression and regression coefficient around unity (bi=1) indicating the stable performance in different environment and wider adaptability.

Yield Stability Analysis in Maize Hybrids of Southwest China under Genotype by Environment Interaction Using GGE Biplot

Selecting superior genotypes across different environments is vital for varietal release, crop planting, and commercial use. Therefore, the objectives of this research were to appraise the performance of hybrids approved in recent years in diverse environments, and recommend high-yielding and stable genotypes for wider adaptation. Fourteen single cross maize hybrid genotypes (G), including a check, were implemented across ten environments (E) in two crop seasons (2020 and 2021). The combined analysis of variance revealed that G, E, and their interactive (GEI) significantly (p < 0.01) affected the grain yield. Moreover, the mean grain yield ranged from 9333 kg ha−1 for HH-2 (2021) to 13,195 kg ha−1 for LD-18 (2020). The “which won where” GGE biplot revealed the existence of mega environments with their own best hybrids (LD-18 and LD-29 in 2020; LD-18, LD-19, and YY-1506 in 2021). The “mean vs. stable” GGE biplot suggested that LD-18 and ZY-811, with highest/middle productive and high stability across 10 environments, were closest to the ideal genotype. Furthermore, the “discriminating power vs. representativeness” GGE biplot showed that Xuanwei, Yanshan, Gengma, and Shiling were the most the ideal test environments for hybrid selecting, based on their discriminative ability and representativeness. Therefore, the GGE biplot analysis allowed for an efficient selection of high-yielding and stable maize hybrids to guide ecological planting and commercial use.

Comparison of Maize Genotypes Using Drought-Tolerance Indices and Graphical Analysis under Normal and Humidity Stress Conditions.

This study aimed to identify drought-tolerant genotypes and to evaluate and compare the response of genotypes under normal conditions and humidity stress. The experiment was conducted in a Randomized Complete Block Design (RCBD) on 12 commercial single cross hybrids of maize (Zea mays L.) with three replications in two separate experiments under normal and stress conditions. GT biplot was used to compare genotypes under normal conditions and humidity stress. Based on the polygon diagrams’ graphical analysis, KSC206, KSC704, KSC705 and KSC706 genotypes were identified as desirable hybrids. The ranking diagram of genotypes based on ideal genotype also showed that the KSC704 genotype had high desirability in all evaluated traits in normal and stress conditions. TOL, MP, HARM, GMP, SSI and STI indices were used to identify drought-tolerant genotypes, and the genotypes were ranked based on this index. Based on this, KSC260, SC302 and KSC400 hybrids were selected as resistant hybrids. Based on the correlation analysis between drought-tolerance indices, a positive correlation was observed between MP, GMP, HARM and STI indices. Based on the analysis of the PCA on the indices, the first and second principal components were given the titles of grain yield tolerance component under humidity stress conditions and grain yield stability component under normal humidity conditions, respectively. KSC704 was superior to other hybrids in terms of grain yield under normal conditions and stress, and the KSC260 hybrid was identified as a tolerant hybrid in terms of all studied traits under drought stress.

Phule Maharshi-A Single Cross Maize Hybrid for Maharashtra

Phule Maharshi (QMH-1025), a single cross maize hybrid from public sector in Maharashtra is developed from the cross between QMI-1403 x QMI-1401 by hybridization technique. It is high yielding, orange yellow, semi-flint type, midlate maturing, resistant to Maydis leaf blight, Fusarium stalk rot, and moderately resistant to Turcicum leaf blight, Banded leaf & sheath blight and Charcoal rot. It is also resistant to Stem borer (Chilo partellus Sw.) in field condition. It is superior for crude protein and fibre, starch, Mn and Ca over the check Rajarshi and suitable for Kharif and Rabi season. In various states and varietal trials, the maize hybrid QMH1025 consistently recorded best performance. During Kharif season, QMH-1025 recorded 7605 Kg ha-1 grain yield, which was 37.27 percent higher than Rajarshi ( 5540 Kg ha-1) and 24.20 percent higher than the national check Bio.9637( 6123 Kg ha-1). In Rabi season, it recorded 8761 Kg ha-1 grain yield which was 19.60 percent and 29.45 percent higher than the checks Rajarshi (7326 Kg ha-1) and Bio.9637 (6768 Kg ha-1), respectively. Overall QMH-1025 recorded 27.20 percent higher yield ( 8183 Kg ha-1) over the check Rajarshi (6433 Kg ha-1) and 26.95 percent over the national check Bio.9637 (6446 Kg ha-1) in Kharif and Rabi season. The maize hybrid is released under the name ‘Phule Maharshi’ for Kharif and Rabi season for Maharashtra State in 2016.

Mega-environment analysis of maize breeding data from Brazil

The development and recommendation of single cross maize hybrids (SH) to be used in extensive land areas (mega-environments), and in different crop seasons requires many experiments under numerous environmental conditions. The question we asked is if the data from these multi-environment experiments are sufficient to identify the best hybrid combinations. The aim of this study was to critically analyze the phenotype data of experiments of yield, established by a large seed producing company, under a high level of imbalance. Data from evaluation of 2770 SH were used from experiments conducted over four years, involving the first and second crop seasons, in 50 locations of different years and regions of Brazil. Different types of analysis were carried out and genetic and non-genetic components were estimated, with emphasis on the different interactions of the SH with the environments. Results showed that the coincidence of common hybrids in these experiments is normally small. The estimates of the correlations between of the hybrids coinciding in the environments two by two is of low magnitude. The hybrid × crop season interaction was always expressive; however, the interactions of hybrids and other environmental variables were also important. Under these conditions, alternatives were discussed for making with the information obtained from the experiments, can be more efficient on the process to obtain new hybrids by companies.

Optimum Row Ratio for Seed Production of Single Cross Maize Hybrid, Karimnagar Makka-1 for Enhanced Yield and Profitability

This study undertaken during rabi season of 2017 and 2018 at Agricultural Research Station, Karimnagar, Telangana to study the effect of planting row ratios of female: male for seed production of Maize hybrid Karimnagar makka-1. The flowering showed that male inbred has taken 60 days after sowing (DAS) to 50% pollen shedding as against 64 days in both 4:1 and 5:1 row ratios and female showed 50% silking at 63 DAS compared to 66 days in both 4:1 and 5:1 row ratios. The 5:1 row ratio recorded significantly more cob length (18.3 cm). Kernel number (29.5), 100-seed weight (39.3g), grain weight per cob (107.6g), seed yield of (2597 Kg/ha) and net returns (Rs. 3,93,632/ha) compared to 4:1 row ratio (17.9 cm, 27.3, 36.6 g, 99 g, 2094 Kg/ha and Rs. 3,05,132 / ha respectively) indicating 19.3 and 22.5% increased yield and net returns over 4:1 row ratio which in turn resulted significantly higher yield over 3:1 row ratio

Heterosis in relation to genetic divergence in short duration maize (Zea mays L.)

Thirteen lines and three testers were used to produce 39 single cross maize hybrids by line Ítester mating design. The genetic divergence among thirteen lines and three tester of maize were estimated by using Mahalanobis D2 statistic for twelve characters. The genotypes were grouped into five clusters. Cluster I comprised 12 parental genotypes (L1, L2, L3, L4, L5; L6, L7, L8, L9, L11; L12, L13), while Cluster II (T3), III (T1), IV (L10) and V (T2) were mono-genotypic, suggesting more variability in genetic makeup of the genotypes included in these clusters. The correlation coefficients and linear regressions were used to know the effects of parental genetic distance in determining heterosis and per se performance of the hybrids. Parental genetic distance exhibited significant negative association and significant linear regression along with very low coefficient of determination with better parent heterosis (BPH) and non-significant with per se performance of the hybrids. The present investigation, therefore, the parental genetic distance has significant role in determining heterosis and hybrid performance in kharif maize.

SNP-based assessment of genetic purity and diversity in maize hybrid breeding.

Assessment of genetic purity of parental inbred lines and their resultant F1 hybrids is an essential quality control check in maize hybrid breeding, variety release and seed production. In this study, genetic purity, parent-offspring relationship and diversity among the inbred lines were assessed using 92 single-nucleotide polymorphism (SNP) markers. A total of 188 maize genotypes, comprising of 26 inbred lines, four doubled haploid (DH) lines and 158 single-cross maize hybrids were investigated in this study using Kompetitive Allele Specific Polymerase Chain Reaction (KASP) genotyping assays. The bi-allelic data was analyzed for genetic purity and diversity parameters using GenAlex software. The SNP markers were highly polymorphic and 90% had polymorphic information content (PIC) values of > 0.3. Pairwise genetic distances among the lines ranged from 0.05 to 0.56, indicating a high level of dissimilarity among the inbred lines. A maximum genetic distance of (0.56) was observed between inbred lines CKDHL0089 and CML443 while the lowest (0.05) was between I-42 and I-40. The majority (67%) of the inbred lines studied were genetically pure with residual heterozygosity of <5%, while only 33% had heterozygosity levels of >5%. Inbred lines, which were not pure, require purification through further inbreeding. Cluster analysis partitioned the lines into three distinct genetic clusters with the potential to contribute new beneficial alleles to the maize breeding program. Out of the 68 hybrids (43%) that passed the parent-offspring test, seven hybrids namely; SCHP29, SCHP95, SCHP94, SCHP134, SCHP44, SCHP114 and SCHP126, were selected as potential candidates for further evaluation and release due to their outstanding yield performance.