Estimation of genetic variability among different soybean genotypes for yield and quality traits under the agro-climatic condition of Rawalpindi – Pakistan

Soybean is one of the most valuable oil seed crop which is good source of protein and edible oil. Pakistan is facing acute shortage of edible oil and depends on import to satiate the requirement of country every year. Therefore present study was planned to identify promising soybean genotypes for yield and quality traits. The research was conducted in the department of Plant Breeding and Genetics at Pir Mehr Ali ShahArid Agriculture University Research Farm Chakwal Road, during Kharif season 2016. Ten exotic and one local soybean genotypes were evaluated in Randomized Complete Block Design (RCBD). Observations were recorded on the basis of morphological and biochemical characters. The collected data were subjected to statistical analysis for ascertaining the significance of traits. The results showed that an exotic genotype (19-2) performed best regarding yield per unit area (182.19 g/m), followed by genotype KD. For quality character, genotypeB-1(36.11%) performed best for higher protein content and also for oil contents (20.55 %) as compared to local check and other competitive exotic genotypes. Yield per unit area was showed significantly positive correlation with number of secondary branches, biomass yield per unit area, hundred grain weight, protein content, oil content and harvest index while it showed negative correlation with days to flower completion. This study is helpful in generating detailed information on yield and quality traits of soybean that can be used in future soybean breeding programs for the development of high yielding and better quality varieties.


Introduction
Soybean (Glycine max) family leguminosea is an important oil seed crop which was introduced with sunflower in Pakistan few years before.Due to low yield per (average 1178kg ha -1 ) [1], it could not make space in the country so its production remained low.It was grown in a very small area of Pakistan, majority in the Province Sindh and Khyber Pakhton Khan [2].Soybean is a big source of protein, soya oil and soya meal, having highest protein contents (40 to 42%) as compared to others food and edible crops [3].It is leguminous crop containing nitrogen fixing bacteria which are used to increase the fertility of soil.Due to its low production and competition with wheat it is considered as insignificant crop in Pakistan [4].For the selection of any desirable genotype it is necessary to have information about yield parameters and their correlation.If the yield related traits are improved then grain yield could also be increased.To develop high yielding genotypes for plant breeder it is necessary to identify traits related to high yield

Results and discussion
Evaluation of eleven soybean genotypes for different morphological and biochemical traits revealed that highly significant differences were found among all soybean genotypes for all parameters except germination percentage (Table 1).All the genotypes showed significant amount of variability, high range of variability was recorded in germination percentage, plant population, number of primary branches, number of secondary branches, days to 50 % flowering, days to flowering completion, plant height, number of pods per plant, 100 grain weight, biomass yield per unit area, yield per unit area, harvest index, protein and oil content.This high variability indicated that soybean could be improved if selection is made on the basis of these attributes.The results regarding mean square comparison indicated that genetic diversity was found in soybean genotypes for different traits.Results for mean comparisons among different yield and quality related traits which are determined during the study as followed in (Table 2).Maximum germination percentage was recorded in genotype B-1 and KD with germination percentage (77 %).These findings were well supported with Chung et al. [8] and Boroomandan et al. [9] results that germination percentages enhance crop production.Higher plant population was recorded in genotype 35(69.23)and minimum mean value was recorded in genotype SEOTU (32.77), these results are in line with findings of [8,9].The maximum number of primary branches plant -1 was observed in NARC-2 (5.3) and minimum for KY (1.86).Similarly, secondary branches (3.93-1.43)were observed for NARC-2 and SUNGMONG with respect to maximum and minimum values respectively.Our results were in line with the results of Islam et al. [12]and Rasaily et al. [13]who evaluated different soybean genotypes on the basis of these attributes.The data range for days to 50 % flowering (31-50.3)were observed for B-1 and KY whereas days to flower completion maximum was recorded for SEOTU and minimum for B-1 (39) was observed ( The results regarding phenotypic correlation (Table 3) showed that grain yield per unit area was highly positively significantly correlated with biomass yield per unit area, hundred grain weight and was positively significantly correlated with the number of secondary branches.Positive relationship among these characters revealed that selection on the basis of these attributes can increase the soybean yield.It was also negatively significantly associated with days to 50 % flowering and days to flower completion but it has positive relationship for protein and oil content.These findings are in line with the results of Khan et al. [14].These results are contradicted with Arshad et al. [5] due to different genetic material constitution and environmental condition of soybean genotypes.

Table 2 )
[12]ese Results are in line withArshad et al. [5]who concluded that most of the genotypes flowered at the optimum days of 30-35 days after sowing.The results for days to flower completion agree with the findings of Islam et al.[12].Maximum plant height (43.90 cm) was recorded in genotype NARC-2 while minimum plant height (26.06) was recorded in genotype KD.Our results of this parameter are well supported byKhan et al.

of different yield and quality traits of 14 characters studied in 11 soybean genotypes
PP= Plant Population, NPB=Number of Primary Branches, NSB= Number of Secondary Branches per Plant, FG=50%Days50%Flowering, FC=Days to flowering completion, PH=Plant Height, NPP=Number of Pods per Plant, HGW= Hundred grain weight, BM= Biomass yield per unit area, YUA= Yield per unit area, HI =Harvest Index, PC = Protein Content, OC = Oil content.

Table 3 . Phenotypic Correlation coefficient among indicated traits in soybean genotypes
* Significant at 5% level of probability level **Highly Significant at 1% level of probability level