Abstract Germplasm characterization is essential to describe germplasms and establish germplasm diagnostic characteristics and estimate the extent of variation in the gene bank collection. In the current study, totally 94 maize genotypes including 92 accessions obtained from Ethiopian Biodiversity Institute and two standard checks were used and collected eight agronomic and morphological traits. The work was aimed to characterize maize germplasm based on genetic parameters such as heritability (h2) and genetic advance (GA) data analysis. The experiment was carried out during the main cropping season 2016 at Arsi-Negelle research site, Ethiopia. The field was laid down in augmented design without replications. The results indicated that highest heritability value was obtained from the number of cobs per plant (72.66%) and lowest heritability also observed for kernel rows per cob (26.02%). Moreover, the maximum expected genetic advance was obtained from 1000 grain weight (76.28), while the highest genetic advance value was recorded from ear height. Therefore, important characters, number of cobs per plant, and ear height were showed high to moderate heritability and genetic advance. It can be concluded that these characters may be used as a selection tool in future pre-breeding programs.

Keywords: maize germplasm, quantitative traits, heritability, genetic advance

The food crop Maize (Zea mays L.) is well-thought-out as one of the most vital food crop out of the main crop species on the basis of their importance in the global economy. It brings billions of dollars worldwide to the annual income in international market for many countries across a globe.¹ It is highly produced (861 million tons), wheat (655 million tons)² and it is 3rd in area under cultivation among all cereal crops. The total area used for maize production throughout the world is estimated 162 million hectares with an average production of 5195 kg ha^-1.³

It is believed that maize was first introduced to Ethiopia in the 16th or 17th century.⁴ Since then, it has gained a lot of acceptance as a food crop for humans and animals. Central Statistical Authority of Ethiopia indicated that during 2000/2001, the average yield of the country was estimated 1.4 million ha in area coverage and 2.52 million tons in production, that accounts for about 20.9% of the total area and 32.6% of the total annual grain production.⁵ To help the field of global food security gaps of the overgrowing population and to minimize load on wheat and rice crops availability, it is very important to boost the maize cultivation, for the reason that it is not only crucial for the survival of human kind as food crop and animal fodder for cattle but also has promising bright future in the form of using it as bio-fuel, which could be another source of energy. It is hopeful that the productivity of maize has been growing for the last few years, which was estimated to be 3415 kg/ha during 2008-09 and 4268 kg/ha during 2012-13, nevertheless, there is still a big gap for its further improvement programme in its production and productivity.⁶

 Ethiopia has got a lot of potential maize indigenous germplasm and traditional landraces varieties collected in the gene bank and also conserved on the hands of farmers. So, in order to offer wider genetic base population for pre-breeding programs it is mandatory to use the gene bank collection of the present day genotypes for their potentially important traits.⁷ Genetic Variations always plays a key role in for emerging or evolving of a new species survival and adaptability. Whenever there is change the population, the population will have to adapt to survive by itself; the ability of the population to cope up with the changing environment will determine their ability to live with an environmental challenge. Dissimilarity in the populations’ gene pool allows natural selection to act upon traits that allow the population to adapt to the changing environments. The more genetic diversity a population has the more likelihood the population will be able to adapt.⁸ It can be described through different system such as morphological, biochemical and molecular markers parameters. Among these parameters, the morphological characterization parameter is well-thought-out as the initial step or the base for further breeding research work.^9,10 The degree of diversity study has been considered by scientists in other crops as well, such as in Oryzasativa L., sesame ,and in maize respectively.^7,11,12 In the current work, we aimed to calculate maize germplasms for morphological characters; depending on their phenotypic and genotypic variability, heritability and expected genetic advance along with their descriptive statistical value. Therefore, this evidence will be valuable to recognize and determine the position of germplasm collection in Ethiopia and to identify the promising accessions of Maize for further improvement work via breeding.

A total of 92 maize germplasms obtained from Ethiopian Biodiversity Institute (EBI) and two standard checks were used in the study Table 1-3. The selected germplasm was grown at Arsi-Negelle farm site,1,947 m a.s.l. (meters above sea level) and astronomically located at 7^o219'N latitude and 38^o08'E longitude Oromia Region, Ethiopia, during main rainy season 2016. The design used was augmented design without replications of accession in each block except for the checks following.¹³ The Plot size was kept at 9 m long with four rows having row to row and plant to plant distance of 75 and 30 cm respectively. Fertilizers used were Urea and DAP at the rate of 200 and 150 kg, per hectare respectively. Standard cultural practices were followed from seed bed preparation, sowing, data recording and harvesting during the entire crop season. From each plot, 20 samples were chosen randomly to score eight morphological characters such as the number of days taken to 50%flowering in days, plant height in centimeter, cob height in centimeter, number of cobs/plant in numbers, number of days taken to 50% maturity in numbers, length of cob in centimeter, number of kernels/cob and 1000-grain weight measured in gram. Hence, data on eight morphological characters were subjected to the analysis of variance (ANOVA) using Statistical Analysis System (SAS) version 9.0software. Estimation of genetic variability like genotypic coefficient of variability, phenotypic coefficient of variability, broad sense heritability, and genetic advance as percent of the mean was computed based on Singh et al.¹⁴ calculated by using the following formulas:

1.  PCV=$\sqrt{PV}$ Phenotypic Variance x 100/ Grand Mean
2. GCV= $\sqrt{GV}$ Genotypic Variance x 100/ Grand Mean
3. Heritability% (h2) = (GV)$÷$ (PV) x 100
4. Genetic advance (GA)= $\sqrt{PV}$ x h2 x k

Where k is the differential selection and value for k is 2.06 (in broad sense) advance percentage of mean= Genetic advance x 100/Grand Mean.

Descriptive statistics were calculated in order to elucidate the basic traits of the data in this research study. They offer us simple pictures about the sample and the measures and they form the basis of virtually every quantitative analysis of the data, such as mean, minimum, maximum, standard deviation, coefficient of variation and variance for each quantitative character was computed among the genotypes is given in Table 2.The form of variability existed among genotypes were unlike for different morphological characters. The maximum variability in the trait was observed in 1000grain weight (2782.36) followed by number of days taken to maturity (175.91), and number of days taken to flowering (175.91). On the other hand, the statistical analysis of the quantitative variables measured on accessions in Table 1. The result showed that coefficient of variation was found between the range of 6.80 and 34.62%. Hence, the variables such as days taken to 50 % of flowering, plant height, ear height, number of cobs per plant, ear length and 1000 grain weight were recorded a high coefficient of variation (˃10%). Conversely, numbers of days taken to maturity, and kernel rows per cob were found in the range low coefficient of variation (˂10%).

The approximate calculation of genotypic variance, phenotypic variance, genotypic coefficient of variation and phenotypic coefficient of variation, heritability and genetic advance for 8 different variables of the maize accessions are presented in Table 3. The value of phenotypic coefficient of variation was higher than the coefficient of genotypic variance for all the characters studied revealing that the apparent variation is not totally due to the genotypes, but also the influence of environmental factors are involved.

 The highest phenotypic coefficient of variation was recorded form ear height (48.92) followed by number of cobs per plant (35.60) and plant height (23.38). Likewise, the highest coefficient of genotypic variance was observed in ear height (30.91) secondly by number of cobs per plant (25.87) and thirdly by1000 grain weight (10.88). On the other hand, on an average from very high to moderate phenotypic coefficient of variation and genotypic coefficient were obtained for ear height, number of cobs/plant, plant height and 1000 grain weight providing sufficient variability and thus offers scope for genetic improvement through selection for the best or novel traits. According to Singh P ¹⁵ and Abirami S ¹⁶ reported high PCV and GCV values for grain yield per plant and ear height in maize. Moderate PCV values of ear girth, ear length, 1000-grain weight and number of grain rows per cob were reported by Singh P.¹⁵ The estimates of the genotypic coefficient of variation reflect the total amount of genotypic variability existed in the maize germplasms which could likely to be transmitted from parents to the progeny is due to the trait heritability.

The statistical computation of heritability in a broad sense revealed that number cobs per plant trait recorded the highest value of (72.66 %) and moderate for ear height (63.20 %), 1000 grain weight (56.15 %), number of days taken to 50% of flowering is (53.97). The higher estimates results of heritability depicted that selection on the basis of phenotypic performance of genotypes would also be more efficient for further improvement of these promising characters of maize genotypes.¹⁷ Conversely, a low heritability result was recorded for ear length (35.49 %) and plant height (33.33 %), kernel rows per cob (26.02 %). Similar studies have also reported lowest broad sense heritability estimate of 32.29% for days from planting to harvesting and highest value of 99.99% for ear weight with sheath and ear weight without a sheath. Low to high heritability values were obtained by in their research study on nine traits in maize genotypes.^18,19

The highest estimate results of genetic advance as percent of mean (63.68) was computed and obtained for ear height followed by number of cobs/ plant (53.29), and 1000 grain weight (22.42). This indicates that selection would be highly promising for continuous improvement of such novel traits. There was also similar findings were reported by Alake et al.¹⁹ who have recorded highest genetic advance as percent of mean for kernel row per ear (39.49) followed by grain yield/hectare (33.98) and ear length (16.54). Shelling percentage had the lowest result GA (% mean) of 6.42, followed by number of leaves/plant and days to 50% male flowering with 8.09 and 8.36 respectively.

Genetic variations existing in a population of a given crop plays a key role in improvement of that particular crop by using the latest technologies of plant breeding. This study was aimed at identifying and screening genetic diversity in 94 maize germplasms using agro-morphological traits. Hence, in conclusion, the highest estimated results of genotypic, and phenotypic coefficient of variation, heritability and genetic advance were observed for cob height and number of cobs/plant and suggesting sufficient genetic variability. Moreover, it also provides opportunities for maize genetic improvement through selection which is a basic research for further breeding work.

The author highly acknowledged Ethiopian Biodiversity Institute for providing maize germplasm and facilitating necessary support for field experiment.

Authors declare no conflicts of interest.

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