Genetic Diversity Analysis of Ethiopian Elite Chickpea ( Cicer arietinum L . ) Varieties Based on Agronomic Characters

This research aim to assess morphological diversity of the elite chickpea (Cicer arietinum L.) varieties in Ethiopia. Nineteen elite varieties of chickpea in Ethiopia were used to analyze the means and components of variability (genetic, phenotypic and environmental), and interrelationships (genetic and phenotypic) for yield and various other yield components. Such nineteen varieties were planted by the technique of Randomized Complete Block Design (RCBD) and three replications were used. Each genotype was sown in four rows with 4.8 m 2 (1 m x 4.8 m) plots area, with 40 cm and 1 m spacing between plots and blocks, respectively. In each plot, one hundred and sixty seeds were planted, using 10 cm spacing between plants These nineteen elite varieties of chickpea were evaluated for the traits of hundred seed weight, biological yield, grain yield, plant height, days to 50% flowering, number of primary branches, number of secondary branches, number of pods per plant, number of seeds per plant, harvest index and days to 90% maturity. Genetic variations were evident among released chickpea cultivars as confirmed by high phenotypic and genotypic variations for quantitative and qualitative traits. Analysis of variance revealed significant differences among the genotypes for all the characters except hundred seeds weight, days of 50% flowering and grain yield. Strong and positive significant correlation was observed between grain yield, biological yield, number of seeds per plant, number of pods per plant and number of primary branches; showing that their improvement led to yield improvement in chickpea. The result suggested from the mean values of number of seeds per plant, number of pods per plant and days of maturity that chickpea genotypes ICCV-14808, Mariye and ICCV92069 may be used as parents in further breeding program to develop high yielding cultivars. Principal component analysis revealed that quantitative traits contributed a lot to chickpea genetic variability.

grain, self-pollinating legume crop, and it is a basic component of the human diet in many countries (FAOSTAT, 2009).The leading chickpea growing countries in the world are India, Pakistan, Mexico, Turkey, Ethiopia and Myanmar (Keneni et al., 2011).The crop most probably originated from the area of present day Southeastern Turkey and the adjoining areas of Syria (Harlan, 1992).India and Ethiopia have been proposed as secondary centers for diversity of cultivated chickpea (Harlan, 1992).However, Zeven and de Wet (1982) suggested that chickpea has different secondary centers of diversity located in at least four regions: the Near East Region (Comprising the Fertile Crescent); Hindustani Region (basically the current India and East Pakistan); Central Asian Region (with Afghanistan, Western Pakistan, Iran and the southern part of the former USSR); and the Mediterranean Region (including Lebanon and Palestine) (Talebi et al., 2008).Plant genetic resources and the genetic diversity present in them provide an assurance for future genetic progress and an insurance against unforeseen threats to agricultural production (Hari et al., 2008).The studies of genetic diversity of plants are very important for developing high yielding varieties and for maintaining the productivity of such varieties in the plant breeding strategies.The screening and selection for crop improvement would be based more likely on availability of promising genotypes; which solemnly depends on the availability for better agronomic traits coupled with disease resistance, earliness and high yield (Keneni et al., 2011).
Chickpea is the cheapest and readily available source of protein, fats and carbohydrates (Choudhary et al., 2012).Unfortunately, despite its nutritional values and economic importance, chickpea production is very low per hectare in the country (Ethiopia) (Bejiga et al., 1996).This is primarily due to poor genetic makeup of the available cultivars.Genetic variability is a prerequisite for any breeding program, which provides opportunity to a plant breeder for selection of high yielding genotypes.One way to estimate the genetic diversity is based on morphological traits which are the classical methods to distinguish variations based on the observation of the external morphological differences in different geographical regions (Ghaffari et al., 2014, Vienne et al., 2003;Hari et al., 2008).It is the earliest genetic marker used for assessment of variation and still has great importance.Moreover, morphological characters are simple to score and economical to use.In the studies of Ethiopian chickpea morphological characters, the landraces showed considerable variability within and between chickpea populations (Bejiga et al., 1996;Feven, 2002;Melese, 2005).However information on the associations between yield and its various components provide the basis for the selection of improved varieties.The objective of this study is to assess morphological diversity of the elite chickpea varieties of Ethiopia, using quantitative characters of the chickpea varieties.

Studying site
The experiment was conducted in Ethiopia at Debre Zeit Agricultural Research Center (DZARC), which is located in East Shoa zone of Oromia regional state; 47 km in the direction of South East of capital Addis Ababa.The geographic location of DZARC is 8°44'N latitude and 38°58'E longitude, with an elevation of 1860 m.a.s.l.The research center receives an annual rainfall that ranges from 452.8 to 934.2 (ml), with annual mean of 691.5 ml.The temperature of this location ranges from 10.76°C to 27.83°C, with mean annual temperature of 19.32°C.The dominant soil types of DZARC are Vertisols, Mollisols and Alfisols (DZARC, 2009;Melese, 2005).

Experimental materials
Nineteen elite chickpea genotypes were grown at DZARC.All the agronomic practices were carried out throughout crop growing season.The description of the nineteen genotypes along with their origin/source is given in (Table 1).

Experimental design and layout
A Randomized Complete Block Design (RCBD) with three replications was used.Each genotype was sown in four rows of 4.8 m 2 (1 m x 4.8 m) plots area and 0.4 m and 1 m spacing between plots and blocks, respectively.In each plot, one hundred and sixty seeds were planted by using 0.1m spacing between plants.Ten individual plants were tagged randomly from each genotype per plot and used for morphological data recording and the following qualitative and quantitative agronomic characters or morphological traits were recorded, using IBPGR descriptors (IBPGR, 1993).Data were recorded for each variety on a number of days to 50% flowering (DTF) and was recorded at the time when at least 50% plants showed the appearance of first flower.Days taken to maturity (DTM) were calculated from the date of planting to the date when 90% plot turned brown and ready for harvest.Maturity data were recorded for hundred seed weight (HSW), grain yield (GY), plant height (PHT), Number of pods per plant (NPP), Number of seeds per plant (NSP), number of primary branches per plant (NPB), number of secondary branches per plant, biological yield (BYD), and harvest index (HI).For data on plant bases, the mean of ten plants which were randomly selected from the two central rows for the plot bases and the two interior rows were used for data collection.

Statistical procedures
Analysis of Variance (ANOVA) was studied using according to Gomez and Gomez (1984) using SAS (1999) for calculating genotypic, phenotypic and environmental variation components and Least Significant Difference (LSD) test was used for pair wise comparison of means.ANOVA was computed for all quantitative traits to detect the variability present among the nineteen elite chickpea varieties.The analysis of variances was carried out following the standard procedure which is applicable to randomized block design as suggested by Gomez and Gomez (1984), using SAS (1999) statistical computer software.The variation of each morphological trait such as quantitative traits was estimated using simple statistical measures: mean, range, genotypic and phenotypic variances and coefficient of variations.The phenotypic and genotypic variation and coefficient of variations were calculated following the formula suggested by Singh and Ocampo (1977).From the analysis, phenotypic variance, genotypic variance, phenotypic coefficient of variation (PCV), and genotypic coefficient of variation (GCV) were calculated: Where, PCV= phenotypic coefficient of variation and ̅ = Population mean.
Where, GCV= genotypic coefficient of variation and ̅ = Population mean.
However, these genotypes had significantly greater hundred seed weight than all other genotypes.ICCV-93512 and ICCV-14808 genotypes take relatively longer days to mature than all other genotypes, except for Dubie which mature early than the other genotypes.Similarly, genotypes like ICCV-92006, FLIP89-84C, Mariye, ICCL82104 and ICCV-92069 relatively showed high grain yield per plant than all other genotypes.In addition, no significant variation was observed in the flowering days among all the varieties tested.Furthermore, the results suggested the presence of sufficient variability among genotypes for days to maturity, primary and secondary branches per plant, plant height, 100-seed weight, and grain yield per plant.This result is consistent with Rehman et al. (1996) who reported similar results for chickpea genotypes in biological yield, grain yield number of seeds per plant and harvest index.Feven (2002) and Melese (2005) also reported highly significant difference among populations for most of the traits such as days to maturity, grain yield per plant, biological yield per plant and harvesting index; indicating the scope for selection of various morphogenetic traits from these highly diversified genotypes.The report is supported by other authors who reported the presence of genotypic variability in chickpea; such as Kumar et al. (1999), Nimbalkar (2000), Wahid and Ahmad (1999) who observed significant variation for a number of seeds per pod and per plant, seeds per plant, hundred seed weight and yield per plant, respectively.Several chickpea investigations recorded significant genotypic differences among the crop collections studied by them (Chander et al., 2001;Abdalla et al., 2003;Zerihun et al., 2018).

Genotypic and phenotypic coefficient of variation
Mean, range and coefficient of variation of agronomic traits have been widely used to determine the variations available in the population.Moreover, the values of genotypic and phenotypic coefficient of variations, >20%, 10 to 20% and <10% are considered to be higher, intermediate and lower respectively (Getachew et al., 2015).The effectiveness of selection in any crop depends on the extent and nature of phenotypic and genotypic variability present in different agronomic traits found in the population (Arora, 1991;Keneni et al., 2011).For this study, lower coefficients of variation (1.20 to 6.27%) were found for number of primary branches per plant, days to maturity and number of secondary branches per plant; and the results are consistent with the findings of Muhammad et al. (2005).Moderate variations (10.95-19.85)were observed for days to 50% flowering, plant height, hundred seeds weight and harvesting index's per plant and higher (26.69 to 38.23) for grain yield per plant, number of pods per plant, number of seeds per plant and biological yield per plant (Table 4).Similar results were reported by Deressa et al. (2013) and Muhammad et al. (2005).The genotypic coefficients of variation were also found lower for biological yield (6.10%) and moderate for number of primary branches (18.10%); while higher coefficient of variations were observed for days to flowering, plant height, days to maturity, number of secondary branches, hundred seed weight, number of pods per plant, harvest index, number of seeds per plant and grain yield per plant.Moderate genotypic coefficients of variation were observed for days to maturity and number of primary branches (12.73% and 16.90%, respectively).Higher genotypic coefficients of variation were observed for the remaining characters (>20%) (Table 4).Overall, no lower genetic coefficient of variability was recorded in this study.The recorded ranges for the quantitative traits indicated the presence of variation among chickpea genotypes.In this study, the range of quantitative traits for biological yield, number of pods per plant, grain yield, number of seeds per plant and hundred seeds weight showed the existence of considerable variation.However, days to maturity, number of primary and secondary branches had relatively low range that is indicated to be relatively low as compared to the other quantitative traits and the same result were also reported by Muhammad et al. (2005), and Pundir et al. (1991).Rao and Kumar (2000) and Singh et al. (1990) reported low variability for days to maturity, while moderately high phenotypic coefficients of variability was noted by Arora (1991) for primary branches per  plant and 100-seed weight.Khan and Sharma (1999) reported high genetic coefficient of variation for secondary branches per plant.Rehman et al. (1996) and Wahid and Ahmed (1999) reported high estimate of genetic coefficient of variability for plant height and seeds per pod.Getachew et al. (2015) reported high genetic coefficients of variability for seeds per plant and seed yield per plant.High genotypic coefficient of variation indicated the availability of high genetic variation for selection and improvement; while the lower value indicated that selection is not effective for particular character because of the narrow genetic variability (Singh et al., 2003;Upadhaya et al., 2008;Mullualem et al., 2017;Shiferaw et al., 2017).

Correlation coefficients of quantitative traits
The associations among traits are useful for selection of genotypes possessing groups of desired characters.Grain yield per plant had highly significant and positive correlations with biological yield, days to 50% flowering, number of seeds per plant and number of pods per plant, and number of primary branches per plant.The yield components exhibited varying trends of association among themselves (Table 5).In contrast, days to 50% flowering showed negative and insignificant phenotypic correlations with primary branches, secondary branches, number of seeds per plant and hundred seeds weight.Days to 50% flowering showed positive but insignificant correlation with plant height and number of pods per plant.

Conclusions
The phenotypic and genotypic coefficients of variation range for quantitative traits and analysis of variance confirmed the existence of variability among released chickpea varieties.Similarly, coefficient of variation for quantitative morphological traits indicated the availability of variation within the same.In the present study, most of the traits had medium to high variation, implying that there is genetic variability among nineteen released chickpea varieties.The highly strong and positive significant correlation recorded between grain yield and biological yield, days to flowering, number of seeds per plant and number of pods per plant.The positive significant correlation with number of primary branches per plant indicated that the yield components exhibited varying trends of association among themselves and the improvements of one trait will affect yield improvement of chickpea.Therefore, the morphological diversity analysis has shown that there is a considerable genetic diversity among the Ethiopian released chickpea varieties, which can be used for further improvement of the released varieties.

Table 1 .
Details of chickpea (Cicer arietinum L.) varieties used for diversity analysis.

Table 2 .
Mean square for quantitative morphological traits of chickpea cultivars analysis of variance (ANOVA).

Table 3 .
Means of different chickpea genotypes for the yield and various quantitative traits.Means sharing the same letters are non-significant at the 0.05 and NS: non-significant (p > 0.05) probability levels, respectively according to Least Significant Difference (LSD) and CV = Coefficient of variation.HSW, 100 Seed weight; BYD, Biological yield; GY, Grain yield; PHT, Plant height; DTF, Days to 50% flowering; NPB, Number of primary branches; NSB, Number of secondary branches; NSP, Number of seeds per plant; NPP, Number of pods per plant; HI, Harvest index; DTM, Days to 90% maturity.

Table 4 .
Mean, range, phenotypic variance, genotypic variance and environmental variance, phenotypic coefficient of variation and genotypic coefficient of variation of quantitative traits of the chickpea genotypes.

Table 5 .
Principal component analysis of quantitative traits of chickpea genotypes.