Genetic variability of soybean accessions for yield and yield attributing traits through using multivariate analysis

Soybean (Glycine max L. Merril) is the second most important food legume of Nepal, grown either as sole or intercrop with maize or in paddy bund. It has immense potential to increase the area and production due to its yield stability and wider adaptation trait. Its importance increases due to the burgeoning of the poultry and cattle’s farming. Genetic variability is under threat not only in the field but also in the national commodity programs that are meant to be safe heavens. It is the basic requirement for a successful breeding programme. Collection and evaluation of accessions of any crop is a pre-requisite for any programme, which provides a greater scope for exploiting genetic variability. Considering the truths, soybean cultivars were collected from IITA, Nigeria, NAGRC gene bank and local collections studied in depth for morphological characterization using multivariate analyses. An investigation was carried out in the forms of regeneration and observation screening nurseries to assess the variability quantitative traits at Rampur environment and over the years 2012 to 2013. Screening nurseries was carried out in rod row design. Yield and yield contributing traits were analyzed to understand the extent of variability for yield and yield attributing traits. The present study revealed the presence of high levels of variations for nine different morphological traits including yield attributes and seed yield among the soybean accessions. A total of forty diverse accessions of local landraces and exotic lines were evaluated in the subtropical rainfed system of Rampur in the year 2012.Some of high yielding accessions of soybean were 272W, Cobb, G-758, and Puja. Likewise a total of hundred one accessions were evaluated for grain yield and yield parameters during 2013. The research results revealed that high yielding soybean accessions were G-18428, TGX 1990-67F, G-757, V9 (B/pur-9, TGX1990-5F. Under cluster analysis using all the seven morphological traits grouped the 40 accessions into five major groups at the genetic distance of 202.63. It was also found that, among the five clusters, cluster I was the largest and consisted of 32 accessions and the second largest group was the clusters II and IV, and each consisted of three accessions. Likely cluster analysis using all the seven morphological traits grouped the 101 accessions collected from National Agricultural Genetic Resources Centre (Gene Bank) and exotic lines from IITA, Nigeria into five major groups at the genetic distance of 267.82. Among the five clusters, cluster I was the largest and consisted of eighty four accessions and the second largest group was the clusters II consisted of fourteen accessions. The accessions from cluster I and cluster II could be used for hybridization program with the soybean accessions of clusters III, IV and V in order to develop high yielding soybean varieties for further improvement. The first seven principal components were extracted which accounted for about 100% variability among the 104 soybean accessions for all morphological characters. There was rich diversity found in seed coat color of the soybean local landraces. Flower color and pattern of flower were also found diverse among the collected accessions. This study indicated the presence of high levels of genetic variability among the soybean accessions in terms of evaluated characters Keywords— soybean, accessions, genetic variability, cluster analysis, principal component analyses (PCA). International journal of Horticulture, Agriculture and Food science(IJHAF) Vol-4, Issue-3, May-Jun, 2020 https://dx.doi.org/10.22161/ijhaf.4.3.5 ISSN: 2456-8635 www.aipublications.com Page | 109 Open Access


INTRODUCTION
Soybean (Glycine max L. Merril) is the second most important food legumes of Nepal, have a diverse adaptability to varied agro-ecological zones with an altitude ranging from 200-2000 m asl either as sole or intercrop with maize in upland or on paddy bund in low land conditions. It alone shared about 23757 ha area and 28237 MT productions out of total legumes (MOAD, 2013).Soybean is a crop which can provide complete protein, containing eight amino acids essential for human. That means it can play a major role in enriching nutritional standard of foods in developing countries, where human beings are facing protein deficiencies (Samia, 2013).The genetic diversity can be analyzed by morphological, biochemical traits, and molecular marker polymorphisms, analysis of gene marker data enables estimation of the mating system and monitoring of genetic changes caused by factors affecting the reproductive biology of a species. As we know, phenotypic traits are controlled by polygenes and affected by environment, but large numbers of accessions can adapt to environments. The phenotypic data has more polymorphism in genetic diversity and reveal genetic variation indirectly. On the contrary, the molecular data reveal genetic variation directly, but fewer markers have less polymorphism. It is very difficult to obtain molecular data for a large number of accessions that has enough polymorphism to show the genetic diversity of germplasm. So, the morphological traits are the suitable and practical tools for studying the genetic diversity on large numbers of accessions. Agromorphological variation in shape of plants has always been an important means of (i) distinguishing individuals; (ii) controlling source seed production; and (iii) identifying the negative traits those effects on yield, the genetic diversity centers of annual wild soybean and the soybean lines resistance to pod shatter, drought, pests or disease (Truong et al.,2005;Malik et al.,2006Malik et al., , 2007. The soybean germplasm show a wide range of phenotypic variation in terms of flower color, days to maturity, plant height, number of pod per plant, seed number per pod, and seed yield. Pod shape is one of the important descriptors for evaluating soybean genetic resources (IPGRI, 1998). Truong et al., 2005 tested the applicability of elliptic Fourier method for evaluating genetic diversity of pod shape in soybean accessions and concluded that principal component scores based on elliptic Fourier descriptors yield seemed to be useful in quantitative parameters not only for evaluating soybean pod shape in a soybean breeding program but also for describing pod shape for evaluating soybean germplasm. For an effective breeding program for crop variety development, the analysis of genetic diversity is one of the useful tools and plays a vital role in identification of superior lines. Moreover, better knowledge on genetic variability could help to achieve long-term selection gain. In the present study, genetic variability of the available soybeans accessions was investigated through using morphological traits. The objective of this study is to understand the genetic variability of soybean germplasm derived from IITA, IVRDC and local landraces. This information will be very useful for rational management and allow breeders to better understand the evolutionary relationships among accessions and to develop strategies to integrate useful variability into their breeding programs.

Experimental Design and Setting the Experiment:
The experiments regeneration nursery, observation screening nursery were laid out in rod-row design with non-replicates. Seeds were sown at the spacing of 50 cm between rows and 10-15 cm between plant to plant in a row. Each entry was grown in 2 rows in screening nurseries keeping plant-to-plant distance of 8-10 cm in rows.

Intercultural Operations:
Urea, Diammonium Phosphate(DAP) and Murat of potash (MOP) were used as basal dose during final land preparation at 9, 87 and 33 kgha −1 , respectively to supplement the recommended dose of chemical fertilizers @ 20:40:20 N: P2O5: K2O kg/ha after final land preparation. Intercultural operations like weeding, thinning, application of pesticide, and so forth were done as recommended and when necessitated for proper growth and development of plants in each plot. Harvesting was done depending upon the maturity of the plants in each plot.

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Seeds per pod (number) Total number of seeds in a pod 100-seed wt (g) One hundred seeds randomly counted and then weighed Seed yield per plant (g) Weighing the total number of seeds produced in a plant Seed yield (kg per ha) Weighing the seeds produced in a plot and then converted into kg per ha

III. RESULTS AND DISCUSSION 3.1 Genetic variability of soybean screening nurseries
A total of forty diverse accessions of local landraces and exotic lines were evaluated in the subtropical rainfed climate of Rampur chitwan in summer season of the year 2012. Variation was observed in agro-morphological traits like days to flower, days to maturity, plant height, seeds/pod, number of pods/plant, grain yield and hundred seed weight varied among accessions ( Table 2). Days from sowing to flowering varied from 62 days in G8514 and G-757 to 39 days in TH227.Days from sowing to 90% maturity varied from 139 days in Gorkha local to 111 days in TH227.Number of pods per plant varied from 97 pods in Salyan-2 to 20 pods in Tandi collection # 1. Plant height ranged from 88 cm in PI200525 to 31 cm in Collection # 1 Mangal Bazar. Number of seeds per 10 pods ranged from 25 seeds in Gorkha local 1, Tandi collection no.1 and V-5 to only 13 seeds in TK-5. Hundred seed weight varied from 25.5 g of Tandi collection # 2 to 5.2 g of TH227. Some of high yielding accessions of soybean were 272W (2195 kg/ha), Cobb (1588kg/ha), G-758(1415 kg/ha) and Puja (1282 kg/ha). Early maturing accessions were TK-5, TH-227, V-3 and V-5(111 days).
Likewise a total of hundred one accessions including two checks (Puja and Cobb) were evaluated for grain yield and yield parameters during 2013. Early plant stand, days to flowering, days to maturity, plant height, seeds/pod, number of pods/plant, grain yield and two hundred seed weight varied among accessions (Table 5). Days from sowing to maturity varied from 108 days in the accessions CM9112, SJ-4, Co169, IPBSY1178, G-758, PI94159, Salyan-2, C2019 to 134 days in TGX1989-41F, V8 and V10. Plant height ranged from 10 cm in C2015 to 176 cm in C2017. Highest number of pods per plant was found in C2022 (263 pods) and lowest number of pods was found in TH227 (34 pods only). Hundred seed weight varied from 4 g of C2021, C2023, C2020 to 24 g of C2026. Table 5  They found variability among genotypes for most studied characters. In the study large variation was found in days to maturity, pods per plant, plant height and grain yield. This data indicated that there is genetic and physical variability in soybean accessions and it is one of the best options to select the best lines for pre-breeding and hybridization program. The results are supported with the findings of Rasaily et al.
(1986), which performed considerable genotypic variability for seed yield. Funnah and Mak (1978) also conducted field trials and found that some varieties yielded over 2000 kgha-1. Dadson (1976) also evaluated different cultivars of soybean and revealed highest seed yields of 2.0 -2.46, 1.18 -1.88, 1.29 -1.59 and 1.21 -1.24 t h-1 were given by cultivars Davis, Hardee, Improved Pelican and Williams, respectively. Ghatge and Kadu (1993) found the similar results and observed high variability for seed yield.

Cluster Analysis
Cluster analysis using all the seven morphological traits grouped the 40 accessions into five major groups at the genetic distance of 202.63 (Table 2, 3 , Figure 1). It was also found that, among the five clusters, cluster I was the largest and consisted of 32 accessions (14 local landraces and 18 exotic lines). Under the cluster I characterized as the early flowering, early maturity and lower yield. This cluster represented 80 % of the total accessions i.e. Coll#3 Mangal bazar, Dhankuta , G-7959, Coll # 1 Mangalbazar, G-8754, SJ-4, IPBSY178, PI94159, Salyan-2, TGX311-23D, 7521-  ), AGS-367, G-757, PI200525, PI368055, TK-5, TGX1925-1F,  Gorkha Local-1, Coll#5 Sikre, Tandi Collection #1, TH227, V-1,V-2,V-3,V-5,V-6,V-8, Tandi Collection #2 and the second largest group was the clusters II and IV, and each consisted of three accessions. These two clusters II and IV represented 7.5% each. These groups had characterized as the moderate maturity and highest yielder. The smallest group was clusters III and V, and each cluster contained only one accessions. The dendrogram based on the quantitative traits of forty soybean accessions was constructed as presented in figure 1. Distances among different Cluster centroids of soybean accessions are presented in Table 3 & 4.
Distances among different Cluster centroids of soybean accessions are presented in Table 8 3

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to maturity, pods per plant, seeds per pod, grain yield and hundred seed wt. and negatively contributed with plant height. PC4 accounted for 11.8% of the variation and positively correlated with days to flower, days to maturity and seeds per pod. PC5 accounted for 10.9% of the total variation and was correlated positively with the days to flower, seeds per pod(0.118) and grain yield(0.421) while remaining variables contributed negatively correlated. PC6 accounted for 6.6% of the total variation and was correlated positively with the days to flower, pods per plant, grain yield and hundred seed weight while days to maturity, plant height, and seeds per pod contributed negatively. PC7 accounted for 5.5% of the total variation and was correlated positively with the days to flower, pods per plant, plant height and seeds per pod, while days to maturity, grain yield (-0.614) and hundred seed weight contributed negatively( Table 10).

Seed Coat Color
There was high diversity found in seed coat color of the soybean local landraces collected from seven districts namely Baitadi, Dadeldhura, Doti, Jumla, Kailali, Kalikot and Muguof mid and far western region of Nepal (Annex ii). The seed coat color was keenly documented after harvest of the crop. Out of thirty threeaccessions, thirteen of them had black seed coat color; two had buff, one grey, three imperfect black, two reddish brown, eight yellow and remaining four had yellowish white seed coat color.

Flower color and phenotypic traits
Flower color and pattern of flower were also found diverse among the collected accessions. Out of the thirty three local landraces, twenty one had white flower color, four had purple throats, and three had purple flower. Some of the five landraces had trailing type, typical little leaves like wild type along with purple flower colors (Annex ii).

IV. CONCLUSIONS
In plant breeding, generation of new genotypes from the existing ones with improvement in plant traits is the main objective. The present study revealed the presence of high levels of variations for nine different morphological traits including yield attributes and seed yield among the soybean accessions. A total of forty diverse accessions of local landraces and exotic lines were evaluated in the subtropical rainfed climate of Rampur chitwan in summer season of the year 2012. Variation was observed in agro-morphological traits. Some of high yielding accessions of soybean were 272W,Cobb, G-758, and Puja. Likewise a total of hundred oneaccessions were evaluated for grain yield and yield parameters during 2013. The research results revealed that high yielding soybean accessionswereG-18428, TGX 1990-67F, G-757, V9 (B/pur-9, TGX1990-5F, Co 157, Chatewan-9, TGX1990-93F, V7 (B/ pur-7), C2020and G-8514. However mean yield performances of soybean accessions over the years affirmed soybean cultivars G-757, G-758, G-8586, V8 (B/pur-8), 272 W were the better performer than the check Cobb. Under cluster analysis using all the seven morphological traits grouped the 40 accessions into five major groups at the genetic distance of 202.63. It was also found that, among the five clusters, cluster I was the largest and consisted of 32 accessions and the second largest group was the clusters II and IV, and each consisted of three accessions. The smallest group was clusters III and V, and each cluster contained only one accessions. Likely cluster analysis using all the seven morphological traits grouped the 101 accessions collected from National Agricultural Genetic Resources Centre (Gene Bank) and exotic lines from IITA, Nigeria into five major groups at the genetic distance of 267.82. Among the five clusters, cluster I was the largest and consisted of eighty four accessions and the second largest group was the clusters II consisted of fourteen accessions. The smallest group was clusters III, IV and V, and each cluster contained 1, 2, 1 accessions respectively. To obtain greater heterosis, accessions having distant clusters could be used as parents for hybridization program. The accessions from cluster I and cluster II could beused for hybridization program with the soybean accessions of clusters III, IV and V in order to develop high yielding soybean varieties for further improvement. The first seven principal components were extracted which accounted for about 100% variability among the 104 soybean accessions for all morphological characters. There was high diversity found in seed coat color of the soybean local landraces. Out of thirty three accessions, thirteen of them had black seed coat color; two had buff, one grey, three imperfect black, two reddish brown, eight yellow and remaining four had yellowish white seed coat color. Flower color and pattern of flower were also found diverse among the collected accessions. Out of the thirty three local landraces, twenty one had white flower color, four had purple throats, and three had purple flower. Some of the five         ,TGX 1990-79F, TGX1835-10E, TGX1904-6F,  TGX1987-10F, TGX1987-14F, TGX1988-3F, TGX1988-5F,TGX1989-20F, TGX1989-21F, TGX1989-41F, TGX1989-45F, TGX1990-101F,  TGX 1990-38F, TGX1990-47F, TGX1990-57F, TGX1990-94F,  TGX1990-97F, TGX1991-10F, TGX311, TH-227,TK