Maize Improvement Research Articles

Identification of bread wheat genotypes with superior grain yield and agronomic traits through evaluation under rust epiphytotic conditions in Kenya

Bread wheat (Triticum aestivum L.) cultivars adapted to specific environments and resistant to prevalent pathogens are preferred for obtaining high yield. This study aimed to identify wheat genotypes with superior grain yield (GY) and yield associated traits from 168 genotypes of International Maize and Wheat Improvement Center’s 13th Stem Rust Resistance Screening Nursery evaluated over two seasons during 2019 and 2020 under high disease pressure of both stem rust (SR) and yellow rust (YR) in a 21 × 8 α-lattice design with 3 replications in Kenya. Effects due to seasons were significant for YRAud, SRAud, 1000-kernel weight (TKW), days to heading (DH), plant height (PH) and number of spikelets spike−1 (SS), while genotypes and genotypes × season interaction effects were significant for all traits except number of kernels spike−1. Respectively, heritability values of 0.95, 0.93, 0.87, 0.86, 0.77 and 0.75 were observed for area under disease progress curve for SR (SRAud), YR (YRAud), TKW, DH, biomass (BM) and GY. Path analysis showed positive direct effects on GY via PH, SS, BM, and TKW. Biplot analysis identified 16 genotypes with superior desirable traits GY, BM and harvest index. The SR contributed the highest reduction in GY and TKW while YR contributed the most reduction in BM. These identified genotypes with superior GY combined with adequate resistance to both SR and YR are potentially valuable resources for improvement of locally adapted wheat cultivars.

Assessment of Egyptian Maize Hybrids for Their Capability of Plant Regeneration using Immature Embryo Culture

The aim of this research was to determine the regeneration capability of five maize hybrids (Syngenta hybrid, Three-way hybrid (324), Single cross hybrid P344 (Pioneer), Single cross hybrid 30N 11 (Pioneer) and Three-way hybrid (321)) using immature embryo explants with four medium protocols. The analysis of variance for in vitro culture traits of explant response indicated that callus induction, callus weight and embryogenic callus significantly responded to maize genotypes, medium protocols and their interaction. Also differences among maize hybrids were highly significant for shoot formation (%), while they were not significant for root formation (%). The four medium protocols indicated highly significant differences for root formation (%) and shoot formation (%). Three-way hybrid (324) and Single cross hybrid 30 N11(Pioneer) had the highest induction frequency of shoot formation on medium protocol D. Both maizehybrids on medium protocol D could be successfully utilized for the in vitro selection studies for maize improvement.

Multi-generation genomic prediction of maize yield using parametric and non-parametric sparse selection indices

Genomic prediction models are often calibrated using multi-generation data. Over time, as data accumulates, training data sets become increasingly heterogeneous. Differences in allele frequency and linkage disequilibrium patterns between the training and prediction genotypes may limit prediction accuracy. This leads to the question of whether all available data or a subset of it should be used to calibrate genomic prediction models. Previous research on training set optimization has focused on identifying a subset of the available data that is optimal for a given prediction set. However, this approach does not contemplate the possibility that different training sets may be optimal for different prediction genotypes. To address this problem, we recently introduced a sparse selection index (SSI) that identifies an optimal training set for each individual in a prediction set. Using additive genomic relationships, the SSI can provide increased accuracy relative to genomic-BLUP (GBLUP). Non-parametric genomic models using Gaussian kernels (KBLUP) have, in some cases, yielded higher prediction accuracies than standard additive models. Therefore, here we studied whether combining SSIs and kernel methods could further improve prediction accuracy when training genomic models using multi-generation data. Using four years of doubled haploid maize data from the International Maize and Wheat Improvement Center (CIMMYT), we found that when predicting grain yield the KBLUP outperformed the GBLUP, and that using SSI with additive relationships (GSSI) lead to 5–17% increases in accuracy, relative to the GBLUP. However, differences in prediction accuracy between the KBLUP and the kernel-based SSI were smaller and not always significant.

Heavy metals immobilization and improvement in maize (Zea mays L.) growth amended with biochar and compost

Soil with heavy metals contamination, mainly lead (Pb), cadmium (Cd), and chromium (Cr) is a progressively worldwide alarming environmental problem. Recently, biochar has been used as a soil amendment to remediate contaminated soils, but little work has been done to compare with other organic amendments like compost. We investigated biochar and compost's comparative effect on Pb, Cd, and Cr immobilization in soil, photosynthesis, and growth of maize plants. Ten kg soil was placed in pots and were spiked with Pb, Cd, and Cr at concentrations 20, 10, 20 mg kg−1. The biochar and compost treatments included 0, 0.5, 1, 2, and 4% were separately applied to the soil. The crop from pots was harvested after 60 days. The results show that the highest reduction of AB-DTPA extractable Pb, Cd, and Cr in soil was 79%, 61% and 78% with 4% biochar, followed by 61%, 43% and 60% with 4% compost compared to the control, respectively. Similarly, the highest reduction in shoot Pb, Cd, and Cr concentration was 71%, 63% and 78%with 4% biochar, followed by 50%, 50% and 71% with 4% compost than the control, respectively. The maximum increase in shoot and dry root weight, total chlorophyll contents, and gas exchange characteristics were recorded with 4% biochar, followed by 4% compost than the control. The maximum increase in soil organic matter and total nitrogen (N) was recorded at 4% biochar application while available phosphorus and potassium in the soil at 4% compost application. It is concluded that both biochar and compost decreased heavy metals availability in the soil, reducing toxicity in the plant. However, biochar was most effective in reducing heavy metals content in soil and plant compared to compost. In the future, more low-cost, eco-friendly soil remediation methods should be developed for better soil health and plant productivity.

GENETIC DIVERGENCE AMONG MAIZE (ZEA MAYS L.) INBRED LINES USING MORPHOMETRIC MARKERS

Genetic divergence study is imperative in breeding programmes in order to select distant parents. Forty maize inbred lines were assessed using morphometric markers to identify the potential inbred lines for yield and its component traits. The inbred lines were raised in α-RBD design replicated twice during kharif 2019. The morphological diversity analysis was done as per the standard statistical procedures using Mahalanobis D2-statistic. Analysis of variance revealed significant mean sum of squares due to genotypes for all the traits suggesting ample amount of genetic variability present among them. Moderate PCV, GCV and high heritability coupled with moderate genetic advance was observed for grain yield per plant, plant and cob placement height. Grain yield per plant exhibited significant positive correlation with all the traits except days to 50 per cent pollen shed and silking. Path analysis revealed high direct effects of days to 50 per cent pollen shed, harvest index, grains per row and 100 grain-weight on grain yield per plant therefore these morphometric traits would be the best selection indices to select high yielding genotypes. D2-statistics grouped 40 maize genotypes into three clusters. Cluster III has the highest cluster mean values for all the traits.Seven genotypes viz., 4186-4-05-1-1, LM-14, BAJIM-08-27, BIOM 10, LQPM24×1114-5, 9180-2, LDH 5(Vivek-21-1) were superior over the best check on the basis of mean performance and disease resistance and were diverse therefore, could be used in maize improvement program.

Responses of nitrogen efficiency and antioxidant system of summer maize to waterlogging stress under different tillage.

Waterlogging was one of the main abiotic stresses affecting maize yield and growth in the North China Plain, while ridge tillage effectually improved soil environment, enhanced crop stress resistance to waterlogging, and increased grain yield of waterlogged maize. In order to explore the responses of nitrogen (N) efficiency and antioxidant system of summer maize to waterlogging stress under different tillage, a field experiment was conducted to explore N use efficiency, leaf activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), and malondialdehyde (MDA) content of waterlogged maize Denghai 605 (DH605) and Zhengdan 958 (ZD958) under different tillage system (ridge planting and flat planting). Our results showed that ridge tillage was beneficial to ameliorate waterlogging damages on antioxidant system by increasing SOD, POD, and CAT activities, and decreasing MDA content. Moreover, ridge tillage significantly increased N efficiency of waterlogged maize. N translocation amount (NTA), N translocation efficiency (NTE), N contribution proportion (NCP), N harvest index (NHI), and N use efficiency (NUE) of waterlogging treatment under ridge planting system (W-V3+R) for DH605 was increased by 108%, 69%, 60%, 8% and 16%, while ZD958 increased by 248%, 132%, 146%, 13% and 16%, respectively, compared to those of waterlogging treatment under flat planting system (W-V3). Ultimately, ridge tillage led to a significant yield improvement by 39% and 50% for DH605 and ZD958, respectively, compared to that of W-V3. In conclusion, ridge tillage was conducive to retard leaf aging, and enhance nitrogen efficiency, thereby resulting in a yield improvement of waterlogged summer maize.

Silicon-mediated growth promotion in maize (Zea mays L.) occurs via a mechanism that does not involve activation of the plasma membrane H+-ATPase

Silicon (Si)-mediated growth promotion of various grasses is well documented. In the present study, Si-induced changes in maize shoot growth and its underlying mechanisms were studied. Maize plants were grown with various concentrations of Si (0–3 mM) in the nutrient solution. Silicon nutrition improved plant expansion growth. Silicon-supplied maize plants (0.8 and 1.2 mM) showed higher plant height and leaf area compared to no-Si amended plants. It was assumed that Si-induced expansion growth was due to positive Si effects on plasma membrane (PM) H+-ATPase. In this context, western blot analysis revealed an increase in PM H+-ATPase abundance by 77% under Si nutrition. However, in vitro measurements of enzyme activities showed no significant effect on apoplast pH, proton pumping, passive H+ efflux and enzyme kinetics such as Km, Vmax, and activation energy. Further, these results were confirmed by in vivo ratiometric analysis of apoplastic pH, which showed non-significant changes upon Si supply. In contrast, 1 mM Si altered the relative transcripts of specific PM H+-ATPase isoforms. Silicon application resulted in a significant decrease of MHA3, and this decrease in transcription seems to be compensated by an increased concentration of H+-ATPase protein. From these results, it can be concluded that changes in cell wall composition and PM H+-ATPase may be responsible for Si-mediated growth improvement in maize.

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

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

Genome-wide identification and expression analysis of the GA2ox gene family in maize (Zea mays L.) under various abiotic stress conditions

GA 2-oxidases (GA2oxs) are a class of enzymes that inhibit the biosynthesis of bioactive GAs in plants. Although GA2oxs have clear roles in the development and defence responses in Arabidopsis, rice, and wheat, their potential effects on maize remain unclear. This study identified thirteen ZmGA2ox genes in maize and further characterized them using phylogenetic, gene structure, genomic locus, expression pattern analyses and GA content determination. Phylogenetic relationship analysis clearly divided the ZmGA2ox family into three groups—seven in C19-GA2ox class I, three in C19-GA2ox class II, and three in C20-GA2ox class. Evolutionary analysis suggested that ZmGA2ox1;1 and ZmGA2ox1;2, ZmGA2ox3;1 and ZmGA2ox3;2, and ZmGA2ox7;1 and ZmGA2ox7;2 are three pairs of segmental duplicated genes. Prediction of cis-regulatory elements in promoters suggested that ZmGA2ox genes were mainly associated with growth, development, hormones, and biotic/abiotic stress. Therefore, their spatial and temporal expression patterns and responses to various stress treatments were analysed on the basis of published RNA-seq data. Moreover, the changes of ZmGA2ox expression in leaves and roots of maize seedlings was detected under salt, alkali, dehydration, and cold stresses by qRT-PCR. The ZmGA2oxs exhibited obvious expression tendencies or characteristics in various organs under different abiotic stresses. The variations in the expression of three ZmGA2ox genes in the C20-GA2ox class in maize seedling roots showed significant regularity and a clear negative correlation with bioactive GA contents under cold and drought conditions, indicating that these three genes might exert key effects on the regulation of GA synthesis and the response to drought and cold stress. Taken together, this study is useful for further dissection of the effect of ZmGA2oxs on abiotic stress responses and might provide potential targets for the genetic improvement of maize.

Genetic variations in some Egyptian Zea mexicana genotypes based on RAPD and AFLP markers

Maize-Teosinte hybrids are of significant interest to maize breeders as a resource of genetic diversity during the maize domestication process as a genetic pool for maize improvement. This study examines the genetic diversity and population structure of 16 Zea mexicana populations which are currently active in Zea breeding programs in Egypt using Random Amplified Polymorphic DNA (RAPD) and Amplified Fragment Length Polymorphism (AFLP) markers. RAPD analysis (14 primers) produced 141 bands; out of which, 102 (72.3%) were polymorphic. On the other hand, AFLP (5 primer combinations) yielded 276 peaks including 267 (96.7%) polymorphic ones with an average of 53.4 peaks per primer combination. A total of 11 unique RAPD markers were created by 6 primers and identified 8 genotypes. The five primer combinations generated 56 unique amplicons that successfully distinguished 12 out of the 16 genotypes tested. Furthermore, the number of observed alleles (Na), effective multiplex ratio (EMR), and polymorphic information content (PIC) indices showed higher values for AFLP (2.00, 53.4, and 0.21) than for RAPD (1.67, 7.3, and 0.15). Cluster analysis based on Nei and Li genetic distance and an Unweighted Pair Group Method with Arithmetic Mean (UPGMA) revealed 5 main clusters representing the 16 Zea mexicana confirming the population structure analysis obtained. High variability of the studied teosinte genotypes using RAPD and AFLP markers will provide valuable tools for Zea mexicana breeding programs in Egypt.

Identification and characterization of circRNAs in maize seedlings under deficient nitrogen.

Here, deep sequencing results of the maize transcriptome in leaves and roots were compared under high-nitrogen (HN) and low-nitrogen (LN) conditions to identify differentially expressed circRNAs (DECs). Circular RNAs (circRNAs) are covalently closed non-coding RNA with widely regulatory potency that has been identified in animals and plants. However, the understanding of circRNAs involved in responsive nitrogen deficiency remains to be elucidated. A total of 24 and 22 DECs were obtained from the leaves and roots, respectively. Ten circRNAs were validated by divergent and convergent primers, and 6 DECs showed the same expression tendency validated by reverse transcriptase-quantitative PCR. Integrating the identified differentially expressed miRNAs, 34 circRNAs could act as miRNA decoys, which might play important roles in multiple biological processes, including organonitrogen compound biosynthesis and regulation of the metabolic process. A total of 51 circRNA-parent genes located in the genome-wide association study identified loci were assessed between HN and LN conditions and were associated with root growth and development. In summary, our results provide valuable information regarding further study of maize circRNAs under nitrogen deficiency and provide new insights into screening of candidate genes as well as the improvement of maize regarding nitrogen deficiency resistance. CircRNA-miRNA-mRNA co-expression networks were constructed to explore the circRNAs that participated in biological development and nitrogen metabolism.

Rubisco substitutions predicted to enhance crop performance through carbon uptake modelling.

Improving the performance of the CO2-fixing enzyme Rubisco is among the targets for increasing crop yields. Here, Earth system model (ESM) representations of canopy C3 and C4 photosynthesis were combined with species-specific Rubisco parameters to quantify the consequences of bioengineering foreign Rubiscos into C3 and C4 crops under field conditions. The 'two big leaf' (sunlit/shaded) model for canopy photosynthesis was used together with species-specific Rubisco kinetic parameters including maximum rate (Kcat), Michaelis-Menten constant for CO2 at ambient atmospheric O2 (Kc21%O2), specificity for CO2 to O2 (Sc/o), and associated heat activation (Ha) values. Canopy-scale consequences of replacing native Rubiscos in wheat, maize, and sugar beet with foreign enzymes from 27 species were modelled using data from Ameriflux and Fluxnet databases. Variation among the included Rubisco kinetics differentially affected modelled carbon uptake rates, and Rubiscos from several species of C4 grasses showed the greatest potential of >50% carbon uptake improvement in wheat, and >25% improvement in sugar beet and maize. This study also reaffirms the need for data on fully characterized Rubiscos from more species, and for better parameterization of 'Vcmax' and temperature response of 'Jmax' in ESMs.

Response of carbon footprint to plastic film mulch application in spring maize production and mitigation strategy

Producing more food with a lower environmental cost is one of the most crucial challenges worldwide. Plastic mulching has developed as one of the most dominant practices to improve crop yields, however its impacts on greenhouse gas (GHG) emissions during the production life cycle of a crop are still unclear. The objective of this work is to quantify the impacts of plastic film on GHG emissions and to reduce GHG emissions with innovative agronomic practices. Carbon footprint per unit of area (CFa), per unit of maize grain yield (CFy), and per unit of economic output (CFe) were evaluated for three maize cultivation systems: a no mulch system, a conventional plastic mulching system (PM) and a biennial plastic mulching pattern, namely a ‘one film for 2 years' system (PM2), during 2015–2018 in a maize field located on the Loess Plateau of China. The results suggested that PM induced a 24% improvement in maize yields during the four experimental years compared to a no-mulch treatment (NM). However, PM dramatically increased the CFa by 69%, 59% of which was created by the input of the plastic film material, and 10% was created by increases in the soil N2O emissions. The yield improvements from PM could not offset the increases in CFa, and CFy and CFe were both increased by 36%. Shifting from PM to PM2 did not reduce crop yields, but it led to a 21% reduction in CFa and 23% reductions in CFy and CFe due to the reduced input amount of plastic film, decreased soil N2O emissions, and less diesel oil used for tillage. Compared to NM, CFy and CFe were only 5% higher in PM2. This study highlights the necessity of reducing the amount of plastic film input in the development of low-carbon agriculture and shifting from conventional PM cultivation to PM2 could be an efficient option for mitigating GHG emissions while sustaining high crop yields in plastic mulched fields.

Adaptation of Hybrid Maize to Greenbelt and Ironstone Plateau Agro-Ecologies of South Sudan

Maize is a major staple food and source of income for over 90% of the population in South Sudan however, average yield is very low (0.5-0.9 t/ha). Little research has been done on maize improvement in the country and farmers mainly depend on local and unimproved cultivars. Identification and release of adapted and high yielding hybrids may elevate average maize yield (t/ha) among the resource-poor farmers in the country. Improved maize hybrids from the region have not been tested under South Sudanese environments. Objectives of the study were to: (i) determine genotype by environment interactions among some regional maize genotypes; (ii) estimate genetic components and heritability for yield performances; and (iii) identify high yielding maize hybrids adapted to agroecologies of South Sudan. At least 48 maize genotypes including elite hybrids and open-pollinated varieties (OPV) adapted across sub-Saharan Africa and two local cultivars collected from local farmers in South Sudan were evaluated across five locations within greenbelt and ironstone plateau agro-ecologies over three years (2013-2015). Experiments were set up in a 12 × 4 alpha lattice design with 2 replications. Standard agronomic practices were followed and data recorded on yield traits and resistance to major diseases. Across locations and years analysis revealed significant differences among genotypes due to genotype and genotype × environment interactions (P ≤ 0.01). Significant variability (P ≤ 0.01) existed among the genotypes for yield stability across environments. The study identified hybrids SC719 (8.3 t/ha), KH500-22A (8.0 t/ha) and Longe 10H (7.9 t/ha) as the best and stable candidates.

Efficient Targeted Mutagenesis Mediated by CRISPR-Cas12a Ribonucleoprotein Complexes in Maize.

Recent advances in the development of CRISPR-Cas genome editing technologies have made it possible to perform targeted mutagenesis and precise gene replacement in crop plants. CRISPR-Cas9 and CRISPR-Cas12a are two main types of widely used genome editing systems. However, when CRISPR-Cas12a editing machinery is expressed from a transgene, some chromosomal targets encountered low editing frequency in important crops like maize and soybean. Here, we report efficient methods to directly generate genome edited lines by delivering Cas12a-gRNA ribonucleoprotein complex (RNP) to immature maize embryos through particle bombardment in an elite maize variety. Genome edited lines were obtained at ~7% frequency without any selection during regeneration via biolistic delivery of Cas12a RNP into immature embryos. Strikingly, the gene editing rate was increased to 60% on average and up to 100% in some experiments when the Cas12a RNP was co-delivered with a PMI selectable marker gene cassette and the induced callus cultures were selected with mannose. We also show that use of higher activity Cas12a mutants resulted in improved editing efficiency in more recalcitrant target sequence. The advances described here provide useful tools for genetic improvement of maize.

The genetic mechanism of heterosis utilization in maize improvement

BackgroundIn maize hybrid breeding, complementary pools of parental lines with reshuffled genetic variants are established for superior hybrid performance. To comprehensively decipher the genetics of heterosis, we present a new design of multiple linked F1 populations with 42,840 F1 maize hybrids, generated by crossing a synthetic population of 1428 maternal lines with 30 elite testers from diverse genetic backgrounds and phenotyped for agronomic traits.ResultsWe show that, although yield heterosis is correlated with the widespread, minor-effect epistatic QTLs, it may be resulted from a few major-effect additive and dominant QTLs in early developmental stages. Floral transition is probably one critical stage for heterosis formation, in which epistatic QTLs are activated by paternal contributions of alleles that counteract the recessive, deleterious maternal alleles. These deleterious alleles, while rare, epistatically repress other favorable QTLs. We demonstrate this with one example, showing that Brachytic2 represses the Ubiquitin3 locus in the maternal lines; in hybrids, the paternal allele alleviates this repression, which in turn recovers the height of the plant and enhances the weight of the ear. Finally, we propose a molecular design breeding by manipulating key genes underlying the transition from vegetative-to-reproductive growth.ConclusionThe new population design is used to dissect the genetic basis of heterosis which accelerates maize molecular design breeding by diminishing deleterious epistatic interactions.

Introgression of Maize Lethal Necrosis Resistance Quantitative Trait Loci Into Susceptible Maize Populations and Validation of the Resistance Under Field Conditions in Naivasha, Kenya.

Maize lethal necrosis (MLN), resulting from co-infection by maize chlorotic mottle virus (MCMV) and sugarcane mosaic virus (SCMV) can cause up to 100% yield losses in maize in Africa under serious disease conditions. Maize improvement through conventional backcross (BC) takes many generations but can significantly be shortened when molecular tools are utilized in the breeding process. We used a donor parent (KS23-6) to transfer quantitative trait loci (QTL) for resistance to MLN into nine adapted but MLN susceptible lines. Nurseries were established in Kiboko, Kenya during 2015–2017 seasons and BC3F2 progeny were developed using marker assisted backcrossing (MABC) approach. Six single nucleotide polymorphism (SNP) markers linked to QTL for resistance to MLN were used to genotype 2,400 BC3F2 lines using Kompetitive Allele Specific PCR (KASP) platform. We detected that two of the six QTL had major effects for resistance to MLN under artificial inoculation field conditions in 56 candidate BC3F2 lines. To confirm whether these two QTL are reproducible under different field conditions, the 56 BC3F2 lines including their parents were evaluated in replicated trials for two seasons under artificial MLN inoculations in Naivasha, Kenya in 2018. Strong association of genotype with phenotype was detected. Consequently, 19 superior BC3F2 lines with favorable alleles and showing improved levels of resistance to MLN under artificial field inoculation were identified. These elite lines represent superior genetic resources for improvement of maize hybrids for resistance to MLN. However, 20 BC3F2 lines were fixed for both KASP markers but were susceptible to MLN under field conditions, which could suggest weak linkage between the KASP markers and target genes. The validated two major QTL can be utilized to speed up the breeding process but additional loci need to be identified between the KASP markers and the resistance genes to strengthen the linkage.

Use of Wild Progenitor Teosinte in Maize (Zea mays subsp. mays) Improvement: Present Status and Future Prospects

Domestication followed by selective breeding made maize an amazing crop, however, it leads to the loss of many allelic forms of those traits which were subjected to intensive selection. Such allelic forms can be recapitulated by domesticating wild alleles to diversify the germplasm and enhance the potential of maize. Teosinte, the wild relative of maize, possesses diverse novel alleles for resistance to abiotic-biotic stresses, yield improvement as well as quality enhancement. Evaluation of teosinte derived maize lines exhibited significant diversification in several agronomical traits, ear and kernel traits, yield, and adaptation. Quantitative trait loci (QTLs)/genes, after several genetical investigations on different beneficial traits, have been mapped using different mapping populations. Gene complexes in teosinte can be a great scientific weapon for agronomical trait improvement as well as increasing the resiliency. Wild relatives being promising genetic resources have not been investigated and validated comprehensively and therefore remained underutilized. In the paper, we have discussed about wild relatives, their status of utilization and prospects in maize improvement.

Screening of suitable genotype for Bangladesh conditions based on genetic variability and path analysis in F2 white maize populations

AbstractWhite maize is the new maize (Zea mays L.) cultivar in Bangladesh. The country needs high‐yielding white maize varieties for farmers’ cultivation, but developing such variety requires appropriate inbred lines. Here, nine F2 populations of white maize were evaluated through assessment of their genetic variability, heritability, and character association for selection of promising lines based on yield and growth parameters. Analysis of genetic variability showed that there were significant variations among the various genotypes of F2 populations. High heritability coupled with large genetic advances in percentage means were obtained in plant height, cob height, number of branches per tassel, number of cobs bearing node, leaf blade area, and grain yield per plant. The analysis of path coefficient indicated positive direct contribution towards yield per plant through days to 50% tasseling, days to 50% silking, cob height, days to maturity, number of branches of the tassel, cob breadth, and number of grains per row. The results thus indicated that indirect selection based on plant height, days to maturity, cob height, leaves per plants, cob length, number of rows per cob, and number of grains per row are reliable to select the appropriate lines for yield improvement in white maize. In view of the yield and its contributing characteristics, the population of KS 510 has a high yield potential for improvement of the varietal performance of white maize.

Genetic variability, heritability, trait associations and path coefficient analysis of maize (Zea mays L.) inbreed lines

Maize (Zea mays L.) is the first most vital cereal share for the productivity, but the second in its production area coverage next to tef, in Ethiopia. However, its development and productivity are influenced by biotic and abiotic factors. The absence of tolerant maize verities and or inbreed lines also another significant problem. Therefore, the present study was targeted to assess the magnitude of genetic variability, heritability and genetic advance of traits, to verify the genotypic and phenotypic associations between essential characteristics and determine the relationship of features with grain yield and direct and indirect effects using path coefficient analysis. The experiment was conducted at Pawe Agricultural Research Center using 23 inbred lines with RCB design with 3 replications. Results revealed that significant (P<0.01) variations were observed between inbred lines in yield and yield-related traits. Moderate to the high genotypic coefficient of variation, heritability and genetic advance as the percentage of mean values were recorded for plant height, ear height and grain yield. Plant height, ear height and number of ears were observed significant to highly significant positive phenotypic and genotypic associations with grain yield. In contrast, days to 50% anthesis and silk emergence, plant and ear aspects were showed negatively significant associations with grain yield at both genotypic and phenotypic levels. The highest grain yield was recorded from A7033 (8.3 t ha-1), CML197 (6 t ha-1) and CML202 (5.5 t ha-1) and these lines could be best female parents’ foe crop maize improvement programs.