Faba bean (vicia Faba L.) Germplasm Collection and its diversity in Oman

Faba bean (Vicia faba L.) is one of the popular pulse crops grown for traditional consumption, not only in Oman but also in Arabian Peninsula and other countries. In Oman, the famers living in and around high altitude mountain areas mostly grow it. This paper highlights features of variation in seed color and diversity in seed traits found in collected accessions from the joint collecting missions of 2008-2010 between the staff of College of Agriculture, Sultan Qaboos University and the Ministry of Agriculture & Fisheries throughout all the governorates of the Sultanate of Oman. 41 seed samples/accessions were collected from 38 sites. Of these, the highest number of accessions was collected from Batinah South governorate (38) represented mostly by the mountains of Rustaq, followed by the mountains of Interior/Al-Dakhliyah (8), and Dhahira & Buraimi (4). Only one accession was collected from mountains of the Eastern/ Al-Sharqiyah governorates. The seed accessions were found diverse with respect to all seed characters studied, i.e. seed length (cm) and width (cm) and 1000-seed weight (g) besides seed color. The faba bean accessions were classified into 9 genetically diverse clusters based on the Principal Component Analysis, which indicated that the contribution of seed width and 100-seed weight to the total variation existing in indigenous germplasm collected from all the governorates of Oman. It was found from the critical analysis of seed colors that 38 accessions were homogenous (pure) with one color and three were heterogeneous with combinations of colors.


INTRODUCTION
Faba bean (Vicia faba L) is a major legume crop after dry beans, peas and chickpeas (Kumari and Van Leur, 2011). It is used as both food and fodder because of its high lysine-rich proteins, vitamins, minerals and carbohydrates (Crepton et al., 2010). Faba bean has gained greater global attention in recent years because of its ability to gr wide range of soil and climatic conditions for sustainable agriculture in several marginal areas (Nadal Gasim et al., 2015). The Sultanate of Oman is one of the arid countries in the Arabian Peninsula with 85473.10 ha of cultivated agricultural land of which fruits occupy 36.11% followed by perennial and annual fodder crops (39.40%), vegetables (19.72%) and field crops (4.77%) (MAF, 2017). Of the minimum field crop area, the area under faba bean (Vicia faba insignificant and not documented. However, it essential crop during winter between L) is a major legume crop in the world (Kumari and Van Leur, 2011). It is used as both food and fodder because of its high rich proteins, vitamins, minerals and 2010). Faba bean has gained greater global attention in recent years because of its ability to grow over wide range of soil and climatic conditions for sustainable (Nadal et al., 2003 and The Sultanate of Oman is one of the arid countries in the Arabian Peninsula with 85473.10 ha of cultivated agricultural land of which fruits occupy 36.11% followed by perennial and annual fodder crops (39.40%), vegetables (19.72%) Of the minimum field crop Vicia faba L.) is very insignificant and not documented. However, it forms an Plant Genetics Resources Center, The Research Council, November and April among only with few interested farmers in the plains and mountainous areas of N primarily for its edible seeds (beans). Faba bean has been divided into distinct groups based on seed size as small seeded (0.2 to 0.8 g per seed), medium and large seeded ones (1.0 to 2.6 g per seed) which have significance from marketing 2001; Kaur et al., 2014). A range of faba bean ecotypes are grown in Oman under varied ecological conditions for their food and fodder value besides interest in the crop among farming community. Of late, the local indigenous germpl of various crop species like faba bean is slowly facing the serious problem of getting extinct. This is mostly attributed to gradual introduction of high yielding crops of commercial value and shift in land use patterns to either growing high profit yielding crops like vegetables under green houses, hydroponics, etc or to urbanization. The germplasm collections and their conservation would safeguard the rare accessions from their extinct. Worldwide more than 43,500 faba bean accessions are conserved in about 37 global collections of which ICARDA gene bank house the highest of more than 9000 accessions followed by the Chinese Academy of Agricultural Sciences (CAAS) in China, that conserve more L.) is one of the popular pulse crops grown for traditional consumption, not only in Oman but also in Arabian Peninsula and other countries. In Oman, the farmers living in and d high altitude mountain areas mostly grow it. This paper highlights features of variation in seed color and diversity in seed traits found in collected accessions from the joint collecting missions griculture, Sultan Qaboos University and Fisheries from all the governorates of the Sultanate of Oman. 41 seed samples/accessions were collected from 38 sites. Of these, the highest number of accessions was 8) represented mostly by the mountains of Rustaq, Dakhliyah (8), and Dhahira and Buraimi (4). Only one -Sharqiyah governorates. The seed accessions were found diverse with respect to all seed characters studied, i.e. seed length (cm) and s seed color. The faba bean accessions were classified into 9 genetically diverse clusters based on the Principal Component Analysis, which indicated that the seed weight to the total variation existing in indigenous plasm collected from all the governorates of Oman. It was found from the critical analysis of seed colors that 38 accessions were homogenous (pure) with one color and three were heterogeneous ribution License, which permits unrestricted November and April among only with few interested farmers in the plains and mountainous areas of North Oman grown primarily for its edible seeds (beans). Faba bean has been divided into distinct groups based on seed size as small seeded (0.2 to 0.8 g per seed), medium and large seeded ones (1.0 to 2.6 g per seed) which have significance from marketing view point (Zeid et al., A range of faba bean ecotypes are grown in Oman under varied ecological conditions for their food and fodder value besides interest in the crop among farming community. Of late, the local indigenous germplasm of various crop species like faba bean is slowly facing the serious problem of getting extinct. This is mostly attributed to gradual introduction of high yielding crops of commercial value and shift in land use patterns to either growing high elding crops like vegetables under green houses, hydroponics, etc or to urbanization. The germplasm collections and their conservation would safeguard the rare accessions from their extinct. Worldwide more than 43,500 faba bean about 37 global collections of which ICARDA gene bank house the highest of more than 9000 accessions followed by the Chinese Academy of Agricultural Sciences (CAAS) in China, that conserve more

INTERNATIONAL JOURNAL OF CURRENT RESEARCH
Faba bean (Vicia faba l.) germplasm collection and its than 5200 accessions (FAOSTAT, 2016;Duc et al., 2010;Kaur et al., 2014). Several crop germplasm collection missions were held in Oman since early 1990's primarily to conserve indigenous plant genetic resources for future food security of Oman (Guarino, 1990;Osman et al., 2002;AlSaady et al., 2014). In continuation of these efforts, a series of joint collection missions between the Sultan Qaboos University and the Ministry of Agriculture and Fisheries were carried out from different sites within different governorates of Oman from April 2008 to March 2011 to explore the vast indigenous genetic diversity available in legume crops of Oman. This paper presents the results of faba bean (Vicia faba L.) germplasm collecting mission besides the diversity existing in collected indigenous faba bean accessions in respect of few seed traits.

MATERIALS AND METHODS
Seven exploration trips were undertaken from April 2008 to March 2011 in different Governorates of Oman with the support of the staff of Agriculture Development Centers of the Ministry of Agriculture and Fisheries following standard method of collecting missions (IPGRI, 1995;Hay and Probert, 2011;AlSaady et al., 2014) for the collection of seed samples of indigenous germplasm of alfalfa and food legumes like chickpea, faba bean, cowpea, lentil, field pea, mung bean and pigeon pea, and the medicinal legume fenugreek. The collections were made from individual farmers, farmers-fields and stores, and Agriculture Development Centers by recording the crop passport data and site descriptions including GPS data, electrical conductivity and pH of soil and water samples. The sites covered during the trips lied between coastal and interior plains from 12 m to 1,983 m altitude. In all, 156 collecting sites were visited. Indigenous faba bean accessions were collected from 38 sites (Table 1). Seed traits such as seed length and width (cm) and test weight (100 seed) were measured, and seed color and nature of seed samples (pure or mixture) were determined on visual basis. The principal component analysis (PCA) was carried out with the extraction of the components using correlated matrix from the crop collection data on quantitative seed traits using XLSTAT software (XLSTAT, 2017).

RESULTS
41 seed samples/accessions were collected, with the highest of 28 accessions from Batinah South coastal governorate represented mostly by mountainous areas of wilayat Rustaq, followed by Al-Dakhiliyah / Interior governorate (8), Dhahira and Buraimi governorates (4) and the least of only one accession from Sharqiya governorates. There were no accessions collected from either Dhofar (South Oman) governorate or from coastal areas of North and South Batinah governorates.
Variation in seed characters: Seed accessions were found diverse with respect to all but few quantitative seed characters studied like seed length (cm) and width (cm) and 100-seed weight (g) and qualitative trait like seed color (Table 2). Seed length was found varied from 1.180 cm

Principal Component Analysis
The data on three quantitative three seed traits were subjected to the Principal Component Analysis (PCA) to understand which combination seed traits contribute to obtaining high quality of the indigenous faba bean germplasm in terms of their significance and value in marketing. The scree plot of the PCA (Figure 1) indicated that the first two eigenvalues had major proportion of the variance in the dataset as evidenced by the first two PCAs extracted from the components contributing to 91.719 % with PC 1 having eigenvalue of 2.104 and PC 2, 0.648 (Table 3). The PC 1 was positively and equally influenced by seed width (0.894) and 100-seed weight (0.892).      However, the PC 2 was also influenced positively by seed length (0.701) but negatively by seed width (-0.274) and 100seed weight with low values. PC 3 was also positively associated with seed width but with low value (0.354) (Table  4). Similarly, only positive and significant correlation values (r) were found between three seed characters studied viz. seed length vs seed width (0.444*), seed length vs 100-seed weight (0.438*) and seed width vs 100-seed weight (0.752**) ( Table  5). In terms of percent contribution of seed traits to the PCs, both seed width and 100-seed weight together contributed to the extent of 75.822% to PC1 and to the extent of 99.991% to PC3. However, seed length alone contributed to the extent of 75.794 % to PC2 (Table 6). The spread of 41 indigenous faba bean accessions in biplot graph of the first two PCs as X and Y axes clearly indicated pattern of grouping in all the four quadrants of the graph and separated into 9 clusters where the accessions belonging to the same group are in close proximity to form clusters in whichever quadrants of the graph they had occupied due to their similarities ( Figure 2). The number of accessions in clusters were found varied from single (Cluster VIII and Cluster IX) to the highest of 14 in Cluster V. The remaining 6 clusters had accessions ranging from 2 to 9. The accessions of the clusters were found either belonged exclusively to the same governorates like Al-Batinah South (Clusters VI) or to different governorates (Clusters I to V, VII).

DISCUSSION
An array of indigenous faba bean germplasm accessions was collected during the collecting missions from as many as four of seven governorates of the Sultanate of Oman, targeted ( Figure 3). Most of these accessions were acquired from the farmers whose faba bean fields were at high altitude locations. South Batinah represented by the mountainous areas of wilayat Al-Rustaq contributed the highest number to the extent of 68.29 % of accessions, followed by Al-Dakhliyah (Interior) governorate (19.51%), Dhahirah and Buraimi governorates (9.76%). Interestingly, Al-Sharqiya, easten governorates contributed the least of 2.44%. Interestingly, the mountains of North Batinah and Musandam had no contribution to collections perhaps due to water shortage in the area during cropping season. However, southern Dhofar governorate has no tradition of faba bean cultivation (MAF, 2005). The results of critical analysis of seed color of faba bean germplasm accessions at the laboratory indicated least variation in seed coat color pattern but large variation seed size characters (Table 2). These variations observed in seed size among the collected samples of indigenous Omani accessions are in conformity with those observed in previous studies that dealt with either local small or large germplasm collections (Terzopoulos et al., 2003;Kaur et al., 2014;Gasim et al., 2015;Rebaa et al., 2017). In the present study, villages located closely with the collecting sites appeared to have interestingly similar patterns of seed coat color indicating the presence of large amount of homogeneity in the collected faba bean seed samples/ accessions whereas heterogenous seed samples were found in seed samples from three different sites. Thus, variation in seed coat color pattern is attributed to the involvement of hilum/testa colours which are governed by independent or epistatic major genes (Recciardi et al.,1985). In such cases, there is need for intensive purification of seed accessions into sub-homogenous groups with respect to seed color pattern (Ricciardi et al., 1985;Ghasim et al., 2015). The extensive exchange of faba bean landraces among the farmers in the highlands of wilayats of different governorates like South Batinah and Interior governorates were presumably resulted from selections over centuries and adaptation to local climatic and edaphic factors. Constant availability of indigenous landraces with the farmers indicates the existence of local conservation strategy for sustainable production. Genetic erosion of faba bean landraces was perhaps found in both North Batinah and Musandam governorates, as there were no collections. However, in case of Dhofar governorate the faba bean is not traditionally cultivated and hence, not found (  Figure 3). In other governorates like Al-Dakhliyah (Interior), Al-Sharqiya North and South and Dhahirah and Buraimi very less number of samples were obtained as compared to the collections made in the past in Oman (Guaerino, 1990;AlSaady et al., 2018 a & b).This could be because of use of modern high-yielding crops like vegetables, changes in land use pattern for cultivation like greenhouses, hydroponics etc., urbanization, drought periods besides the lack of interest among the farmers these days to grow uneconomical crops like faba beans. The correlation analysis of seed characters showed their significant (p<0.05) and positive associations between each other. Selection of strongly associated character like 100-seed weight can be used to improve seed quality characters that influences yield and their value in marketing (Terzopoulos et al., 2003;Gasim et al., 2015;Gidey et al., 2016).
The results of PCA analysis would be of significance in breeding programs in detecting the appropriate phenotypic characters which contribute higher genetic variations among different genotypes for selecting parents in crossing program to improve the characters of interest for productivity in quantity and quality (Zeid et al., 2001 andDuc et al., 2010;Kaur et al., 2014). In the present study, the results of PCA clearly showed that the quantitative seed traits, studied, positively contributed to PCA1 indicating that this component reflected the potentiality of seed size in faba bean germplasm whereas only seed length contributed positively to PCA2. The existence of wider phenotypic variation among the indigenous faba bean germplasm was further explained by the biplot graph that indicated an overview of the similarities and dissimilarities among the faba bean accessions as well as of the interrelationships between the variables, investigated. The graph characteristically demarcated the faba bean accessions about their scattering pattern based on the first two dimensions/ components into 9 clusters in all the four quadrants, indicating the existence of wide genetic variation for the seed traits, studied. The accessions OMA 102 from Al-Dakhliya (Interior), OMA 189 from South Batinah/ Coast and OMA 80 from Al-Dhahirah governorates occupied extreme positions from the origin of the graph showing that they are genetically distinct accessions whereas other accessions were more concentrated around the origin on PCA2, which indicated their genetic similarity for the seed traits. In the present study, the accessions of certain clusters like cluster VI (South Batinah) belonged to the same governorate whereas the accessions of remaining clusters like I to V and VII were from different governorates. OMA 80 from Al-Dhahirah and OMA 189 from South Batinah were isolated as different clusters (VIII and IX). Considering such a cluster pattern among the faba bean accessions studied, it is suggested that the accessions of different clusters be used in crossing program for improvement of seed characters, as these accessions would be genetically divergent (Zaid et al, 2001 andDuck et al., 2010;Kaur et al., 2014;AlSaady et al., 2018 a and b).