Oil Content and Fatty Acids Composition in Brassica Species

Abstract

Seeds of 20 accessions of six Brassica species including cultivated and five wild relatives were analyzed for oil and fatty acid composition. The results showed that oil content varied from 21 (B. nigra) to 46% (B. napus). Among wild species, B. rapa and B. oleracea had highest oil content (31 and 28%, respectively). The main fatty acids of oleic, linoleic, linolenic, erucic, palmitic, and stearic acids accounted for 89–94% of the total fatty acids in all species. Cultivated species of B. napus had highest oleic acid (61%) and lowest erucic acid (1%) content compared to other studied species. Brassica rapa and B. oleracea had the highest content of erucic acid (41 and 46%, respectively). The highest content of linolenic (20%) and linoleic (19%) acid was observed for B. juncea. The results showed that there was high genetic variation among the studied species for oil content and fatty acids composition. This indicates that seed oil of these species is possibly suitable for both human consumption and industrial purposes.

Keywords:

• Canola
• Fatty acid
• Edible oil
• Brassica

INTRODUCTION

Oil crops have great deal of importance for world agriculture and associated industries. Fatty acid composition controls functional and nutritional values of different vegetable oils, varying considerably depending on the plant species. This has motivated researchers to seek new sources of oil or new fatty acids composition within wide varieties of plant species. Presence of genetic variation for fatty acid composition is found to be essential for genetically improving of the oil quality and subsequently developing new cultivars.^[1,^2] Enormous potential plants have been evaluated for their seed oil content and fatty acids profile of which, some have been introduced as the new oilseed species.^[3] Breeding manipulations in oil crops to improve nutritional values, have led to increased oil quality in new genotypes including those with low erucic acid oil content of Brassica species^[4] or new flax cultivars with low linolenic acid among others.^[5]

The Brassicas are served to be one of the most agronomical important oilseeds with a diverse range of species may be used as a variety of oilseed, vegetable, and fodder crops. The main outstanding trait for Brassica species is the high seeds oil content, varying 17 up to 40% in wild relatives.^[6] The major cultivars belonged to Brassica oilseed crops, i.e., B. napus, B. juncea, and B. rapa, with average oil content ranged 45 to 50% have been released thanks to plant breeding science,^[1] and at present, previously mentioned cultivars are the world’s third most important source for vegetable oil.^[7]

The seven major fatty acids were extracted from members of the genus Brassica are found to be palmitic (C16:0), stearic (C18:0), oleic (C18:1), linoleic (C18:2), linolenic (C18:3), eicosanoic (C22:0), and erucic (C22:1) acids. Brassica oil has fatty acids composition in higher genetic variations compared to those contained in other major vegetable oils.^[8] Brassica species seed oil is characterized by significant amount of long-chain monounsaturated fatty acids, mainly erucic acid (C22:1) absented in any other commercial plant oil.^[9] High erucic acid contained oils are useful for industrial applications, but not for human consumption. Therefore, to develop varieties having both commercial free erucic acid as well as those with high erucic acid is a promising objective for breeding programs in Brassica oilseed crops. Other important objectives are the increase of oleic acid and linoleic acid, and the reduction of linolenic acid content.^[10]

Currently, additional breeding targets involving oil composition have emerged, in particular those within field of industrial applications of vegetable oils, since it is possible to transfer gene among species.^[11] For this, wild species (relatives) have been receiving substantial interest as potential sources of genes for cultivated species. Wild species of Brassica genus may be crossed with cultivated one to improve its traits such as seed oil. There are some reports on the fatty acid composition of Brassica^[6,^12] however, to the best of the authors’ knowledge, wild species oil composition has not been studied comprehensively. The present study is aimed to evaluate the oil content and fatty acid composition of Brassica napus and five related species (B. juncea, B. carinata, B. oleracea, B. nigra, and B. rapa) and to investigate the variation for these traits among and within the species. This information can be promising to improve oil content and fatty acid composition in breeding programs.

MATERIALS AND METHODS

Plant Materials

The plant materials involved three cultivars of B. napus, four accessions of B. juncea, three accessions of B. carinata, three accessions of B. oleracea, two accessions of B. nigra, and five accessions of B. rapa (Table 1). Accessions were planted in mid-September of 2011 and arranged in randomized complete block design with three replications under normal cultural practices and plant protection measures. Seeds were harvested when plants attained complete physiological maturity in July 2012. The data on ten plants in each accession were recorded. The mature seeds were used for oil and fatty acid analysis. The experiment was conducted on a Typic Haplargid, silty clay loam soil at Research Farm of Isfahan University of Technology, located in Lavark, Najaf-Abad, Iran (32° 30´ N, 51° 20´ E), with mean annual temperature and precipitation of 14.5°C and 140 mm, respectively. The soil was calcareous, non-saline, and non-sodic with a pH of 8.3. The electrical conductivity and the sodium adsorption ratio of the soil saturated extract were 1.6 dS m⁻¹ and 1.4 (mmol/l)^0.5, respectively. In this region summers are dry and there is usually no rain from end of May to mid of October.

TABLE 1 List of 20 accessions of Brassica evaluated for oil content and fatty acid compositions

Accessions code	Species	Sub-species	Variety	Origin
B.N-4	Brassica napus	−	Slm 046	France
B.N-6	Brassica napus	−	Opera	Germany
B.N-7	Brassica napus	−	Okapi	France
B.J.J-13	Brassica juncea	juncea	−	Romania
B.J-16	Brassica juncea	−	−	Korea
B.J-I-17	Brassica juncea	integrifolia	−	−
B.J.J-36	Brassica juncea	juncea	−	Belgium
B.C.B-18	Brassica carinata	−	BRA927	Ethiopia
B.C.B-19	Brassica carinata	−	BRA1196	Ethiopia
B.C.B-22	Brassica carinata	−	BRA1178	Ethiopia
B.O.G-44	Brassica olreacea	−	Gongylodes	Iran
B.O.A-45	Brassica olreacea	−	Alboglabra	Thailand
B.O.C-52	Brassica olreacea	−	Capitata	Iran
B.N.N-28	Brassica nigra	nigra	Nigra-CR2724	−
B.N.N-29	Brassica nigra	nigra	Nigra-CR2717	Italy
B.R.D-10	Brassica rapa	dichotoma	−	Great Britain
B.R.C-32	Brassica rapa	chinensis	Rosularis	China
B.R.C-35	Brassica rapa	chinensis	Communis	China
B.R.P-61	Brassica rapa	pekinensis	−	China
B.R.P-64	Brassica rapa	pekinensis	−	China

Oil Extraction

For each replication, seeds of the accessions were dried to 5% moisture content using ventilated oven at 40°C for 4 h and then were ground with a blender. Five grams of ground seeds were extracted for oil in the Soxhlet apparatus, using petroleum ether as solvent for 6 h according to the AOCS method^[13] and then oil content percentage was calculated for each sample.

Fatty Acid Profiling

The oil sample from each accession was converted to its fatty acid methyl esters (FAME) according to the method developed by of Goli et al.^[14] One hundred microliters of sodium methoxide (0.5 M) was added to 50 mL sample in 1 mL n-hexane. The mixture was shaken vigorously for 15 min and then allowed to be precipitation and separation. Hexane phase was removed and immediately 1 mL was injected to GC at a split ratio of 20:1. The FAME analysis was conducted on an Agilent 6890N gas chromatography equipped with a Flame Ionization Detector (FID). The column used was a HP-88 (100 m, 0.25 mm i.d., and 0.2 mm film thickness). The temperature program consisted of increasing the temperature first from 150 to 210°C at a rate of 5°C/min and holding for 8 min, then increasing to 240°C at a rate of 5°C/min and holding for 6 min. injector and detector temperatures were regulated 230 and 250°C, respectively. Ultra high-purity nitrogen was used as the carrier gas.

The peak identification was conducted comparing the relative retention times with those of a commercial standard mixture of FAME. The fatty acid content of palmitic (C16:0), stearic (C18:0), oleic (C18:1), linoleic (C18:2), linolenic (C18:3), and erucic acid (C22:1) were measured using a computing integrator and expressed as percentage of oil. An analysis of variance (ANOVA) for a randomized complete block design with two replicates was performed using General Linear Models (GLM) procedure in software SAS statistical.^[15] The least significant difference (LSD) test was used to doing analysis of mean separation. The Correlation procedure (CORR-PROC) of SAS was used to estimate correlation between traits. Phenotypic coefficients of variation (PCV) and genotypic coefficients of variation (GCV) were calculated using the following models:

where, σ_p, σ_g, and μ represent phenotypic variance, genotypic variance, and mean of the traits, respectively.

RESULTS AND DISCUSSION

Variation and Heritability

ANOVA indicated significant differences (p < 0.01) for oil content and fatty acid compositions among the species (Table 2). Statistics for PCV, GCV, and broad sense heritability (h²) are shown in Table 2. Oleic and stearic acid exhibited highest GCV (73 and 76%, respectively) and the lowest one was belonged to palmitic acid (13%). h² ranged from 75% (palmitic acid) to 98% (oleic and stearic acid). In general, high GCV and PCV for a trait indicate the possibility of improvement through selective breeding. However, more gain is achieved when the difference between these two coefficients is trivial. In the present study, slight differences between PCV and GCV for oil content and fatty acid compositions were recorded indicating the negligible effect of environment. At the same time, heritability estimates provide an indication of the potential genetic variation available in a population. High heritability for fatty acids especially for oleic, linoleic, linolenic, and erucic acids suggesting that selection for these fatty acids may be promising for indirect for quality improvement. A large number of industrial oil markets have recently developed for high erucic acid (>500 g kg⁻¹) rapeseed.^[16] High heritability for erucic acid in the present study (92%) indicates the efficiency of selection to develop varieties for industrial purposes. These results are in line with findings of Singh et al. (2002)^[17] and Khan et al. (2008).^[18]

TABLE 2 Analysis of variance for oil content and main fatty acids in six species of Brassica

Source of variation	df	Oil content (%)	C16:0	C18:0	C18:1	C18:2	C18:3	C22:1	U/T^a
Between species	5	266.25**	1.75**	1.05**	1230.72**	49.94**	88.16**	926.02**	0.0004**
Within accession	14	16.70^n.s	0.21^n.s	0.003^n.s	0.56^n.s	1.08^n.s	0.38^n.s	4.31^n.s	0.00002^n.s
Experimental error	20	31.27	0.44	0.08	11.23	4.18	2.07	43.97	0.00008
Mean	−	30.18	3.38	1.34	19.56	16.05	16.61	35.15	0.94
GCV%	−	20.73	13.55	75.73	72.88	17.19	22.79	34.44	0.7
PCV%	−	21.98	15.65	76.46	73.51	18.32	23.22	36.01	0.9
h^2 (%)	−	88.97	75.00	98.09	98.28	88.09	96.24	91.74	71.42

^*,**Significant at 0.05 and 0.01 levels of probability, respectively;

^aThe ratio of unsaturated to total fatty acids;

GCV: genetic coefficient of variation, PCV: phenotypic coefficient of variation, and h²: broad sense heritability.

TABLE 3 Means composition of oil content and main fatty acids for six species of Brassica

Species	Oil content (%)	C16:0	C18:0	C18:1	C18:2	C18:3	C22:1	Total^a	U/T^b
Brassica napus	46.76^a*	4.52^a	2.36^a	61.83^a	17.26^b	6.84^e	1.16^e	93.99^a	0.92^d
Brassica juncea	25.86^e	3.68^b	1.36^b	14.39^c	19.92^a	20.22^a	31.27^d	91.17^c	0.94^c
Brassica carinata	26.93^d	3.27^bc	0.96^c	10.08^e	17.67^b	18.37^c	40.56^b	90.92^c	0.95^ab
Brassica oleracea	28.58^c	3.60^b	0.79^d	15.01^c	12.66^c	14.98^d	46.19^a	93.26^b	0.95^ab
Brassica nigra	21.62^f	3.65^b	1.44^b	12.84^d	17.84^b	19.46^b	34.87^c	89.83^d	0.94^bc
Brassica rapa	31.95^b	2.63^c	1.44^b	18.19^b	13.00^c	16.00^d	41.84^b	93.13^b	0.95^a

*In each column, means with the same superscript letter were not significantly different, using the LSD test (p < 0.05);

^aSum of the studied six fatty acids content;

^bThe ratio of unsaturated to total fatty acids.

TABLE 4 Oil content and fatty acid composition in different accessions of six Brassica species

			Fatty acid composition in the oil (%)
Species	Accession	Oil content (%)	C16:0	C18:0	C18:1	C18:2	C18:3	C22:1	Total^a	U/T^b
B. napus	B.N-4	38.7	5.12	2.67	57.85	18.41	8.42	3.30	95.77	0.92
	B.N-6	44.7	4.15	2.27	63.02	15.71	4.87	0	90.12	0.92
	B.N-7	56.2	4.31	2.14	64.63	17.67	7.25	0	96.10	0.93
B. juncea	B.J.J-13	24.7	4.07	1.34	13.98	20.66	21.31	29.20	90.59	0.94
	B.J-16	31.8	3.28	1.18	12.46	17.46	18.35	38.19	90.92	0.95
	B.J-I-17	26	2.75	1.07	13.35	17.76	18.45	37.90	91.39	0.95
	B.J.J-36	20.4	4.29	1.76	16.69	22.39	22.80	23.75	91.65	0.93
B. carinata	B.C.B-18	25.1	2.85	0.84	8.42	15.03	18.20	45.23	90.57	0.95
	B.C.B-19	29.1	3.54	1.01	10.69	18.03	18.53	38.89	90.70	0.94
	B.C.B-22	26.4	3.10	0.95	10.42	18.86	18.20	39.64	91.17	0.95
B. oleracea	B.O.G-44	29.2	3.61	0.79	14.58	13.30	14.76	46.38	93.43	0.95
	B.O.A-45	26.6	2.17	1.01	17.81	11.44	15.82	46.26	94.51	0.96
	B.O.C-52	28.7	4.13	0.70	14.21	12.46	14.82	46.25	92.57	0.94
B. nigra	B.N.N-28	17.9	4.19	1.51	14.05	15.99	17.66	35.50	88.90	0.93
	B.N.N-29	24.6	3.08	1.42	12.47	18.38	20.03	34.76	90.16	0.95
B. rapa	B.R.D-10	41	2.89	1.84	22.22	14.55	16.09	34.70	92.31	0.94
	B.R.C-32	22.8	3.92	1.80	26.72	17.69	17.74	24.89	92.75	0.93
	B.R.C-35	23.4	2.55	1.18	13.78	12.72	14.95	46.33	91.51	0.95
	B.R.P-61	33.5	2.31	1.20	15.54	11.51	15.88	47.58	94.02	0.96
	B.R.P-64	38.8	2.23	1.22	15.20	11.25	15.75	48.15	93.83	0.96
LSD (0.05%)		8.24	0.97	0.83	4.94	3.01	2.12	9.78	0.72	0.01

^aSum of the studied six fatty acids content;

^bThe ratio of unsaturated to total fatty acids;

C16:0 (palmitic acid), C18:0 (stearic acid), C18:1 (oleic acid), C18:2 (linoleic acid), C18:3 (linolenic acid), and C22:1 (erucic acid).

Oil Content

Six species were differed significantly for seed oil content (p < 0.01; Table 2). The average oil content for B. napus (47%) was significantly higher compared to other species (Table 3). The seed oil content among the accessions varied from 38 to 56% in B. napus, 20 to 31% in B. juncea, 25 to 29% in B. carinata, 26 to 29% in B. oleracea, 17 to 24% in B. nigra, and 22 to 41% in B. rapa (Table 4). Results indicate that high variation was observed for oil content within the accessions of studied species. For example in B. napus cultivars, the highest and lowest seed oil contents were found for Okapi (56%) and Slm046 (38%), respectively (Table 4). Similarly, among the accessions of B. rapa the highest and least oil contents were recorded for B.R.D-10 (41%) and B.R.C-32, respectively (22%).

The great variability of seed oil content in Brassica species denoted to their potential for exploitation in future breeding programs and substantiated findings from other researchers.^[19,^20] The seed oil content of cultivated rapeseed (B. napus) was higher compared to the wild ones, so that these was not far from our expectations and was conformed to those previously reported.^[21] This species has been domesticated for a long time and grown for oil production, therefore, it has been subjected to be selected for higher seed oil content.

Accessions of wild species exhibited considerable variations for oil content. Some accessions in B. rapa and B. oleracea showed higher seed oil content and were in the range of seed oil content observed for cultivated genotypes. These results denote genetic potential of these species to be used directly for oil production or as a source of desirable genes in breeding programs of Brassica genus. Backcrossing programs are known to be a useful tool to improve oil content of inter-specific hybrids to an acceptable level. The seed oil content in the accessions of other species was low indicating that these species may provide less genetic potential for seed oil content. Nevertheless, these species may be a good pool of genes to improve the other traits of rapeseed.

Fatty Acid Profile

The results from ANOVA for fatty acids compositions (Table 2) revealed significant differences among six species (p < 0.01). The most principle fatty acids of Brassica species analyzed were the unsaturated fatty acids of linoleic (12.66–19.92%), oleic (10.08–61.83%), linolenic (6.84–20.22%) and erucic acid (1.16–46.19%), and the saturated fatty acids of palmitic (2.63–4.52%) and stearic (0.79–2.36%; Table 3). The six fatty acids composed 93.99, 91.17, 90.92, 93.26, 89.83, and 93.13% of the seed oil in the species of B. napus, B. juncea, B. carinata, B. oleracea, B. nigra, and B. rapa, respectively (Table 3). Unsaturated fatty acids to total (U/T) ratio in the accessions varied 0.92 to 0.95 (Table 3). Cultivated rapeseed of B. napus showed slightly lower erucic and linolenic acid, but a higher content of palmitic, stearic, and oleic acids (Table 3). The same value of palmitic (C16:0) fatty acid for other species were obtained so that they did not differed significantly. The highest linolenic (20.22%) and linoleic (19.92%) acid contents were observed for B. juncea species (Table 3).

Fatty acids content showed wide variations in the species, as well as seed oil of the accessions (Table 4). Oleic acid content varied from 57.85 to 64.63% in B. napus, 12.46 to 16.69% in B. juncea, 8.42 to 10.69% in B. carinata, 14.21 to 17.81% in B. oleracea, 12.47 to 14.05% in B. nigra, and 13.78 to 26.72% in B. rapa. Oleic acid is found to be one of the main unsaturated fatty acids playing fundamental role in human nutrition. In the present study, B. napus showed higher oleic acid content but the most remarkable variation for oleic acid was found in B. rapa (Table 4). Other species showed no clear differences among accessions. High oleic acid contained oils are greatly resistant to heating and oxidation and suitable for wide variety of uses. Linoleic acid content in the studied germplasms varied 11.25 to 22.39%. Linoleic acid content varied from 15.71 to 18.41%, 17.46 to 22.39%, 15.03 to 18.86%, 11.44 to 13.30%, 15.99 to 18.38%, and 11.25 to 17.69% in the B. napus, B. juncea, B. carinata, B. oleracea, B. nigra, and B. rapa, respectively. Linolenic acid content were varied from 4.87 to 8.42% in B. napus, 18.35 to 22.80% in B. juncea, 18.20 to 18.53% in B. carinata, 14.76 to 15.82% in B. oleracea, 17.66 to 20.03% in B. nigra, and 14.95 to 17.74% in B. rapa. The highest within variation for palmitic acid content was observed in B. oleracea (2.17 to 4.13%). Erucic acid content varied from 0 to 3.30%, 23.75 to 38.19%, 38.89 to 45.23%, 46.25 to 46.38%, 34.76 to 35.50%, and 24.89 to 48.15% in B. napus, B. juncea, B. carinata, B. oleracea, B. nigra, and B. rapa, respectively (Table 4).

Erucic acid is one of the most important fatty acids in mostly found within Brassica genus. This 22-carbon fatty acid is harmful to the human health. In the present study, cultivars of Okapi and Opera (from B. napus) were found as free-erucic acid genotypes. Genotypes without this fatty acid, are nutritionally rated in the highest level. Generally, zero-erucic acid genotypes are belonged to B. napus and B. rapa^[9] and have been also developed in B. juncea^[2] and B. carinata.^[22] In this study, some accessions showed very high erucic acid content. Generally, high erucic acid oil is useful for industrial applications^[16] and is valuable raw material for manufacture of industrial products such as plasticizers, detergents, surfactants, polyesters among others.^[23] Currently, the development of genotypes with very high erucic content is a priority in Brassica breeding.^[7] One of the most useful breeding programs is re-synthesis of the amphidiploids species B. napus from genotypes of their diploid ancestors’ B. oleracea and B. rapa with high erucic acid content.^[7] In this study most accessions of B. oleracea and B. rapa had more than 46% erucic acid which was in agreement with previous reports.^[24,^25] Nevertheless, no accessions of B. nigra with similar high levels of erucic acid have been found in this study. It limits the possibilities to re-synthesize very high erucic acid of B. carinata or B. juncea from B. nigra as one of the diploid ancestors.^[25]

The nutritional properties of Brassica seed oil, like other fats and oils, are dependent on its fatty acids composition, particularly the amount of oleic, linoleic, linolenic, and erucic acids in turn has great deal of importance in terms of in human nutrition. High oleic acid oils have been shown to be have equivalent heat stability to saturated fats and are, therefore, suitable substitute for them in commercial food-service applications entailing for long-life stability. Therefore, it can be heated to a higher temperature without smoking, so that the cooking time can be reduced and as a result, food take up less oil.^[26] In addition, high oleic acid oil has cholesterol lowering properties; while saturated (palmitic and stearic) fatty acids tend to raise blood cholesterol levels considerably.^[27] Vegetable oils contained high content of C18:1 is reviving much attentions for nutritional and industrial applications. The important objective to enhance oil quality is to reduce levels of polyunsaturated fatty acids and their substitution by monounsaturated C18:1.^[28] In this study cultivars of B. napus exhibited the highest content of oleic acid, in turn may be used for nutritional purposes. At the same time, the nutritional quality of the Brassica oil can be undertaken for improvement by increasing the dietary essential linoleic acid (C18:2) contents and decreasing the linolenic acid (C18:3) contents.^[23] Linoleic acid and its derivative fatty acids are essential fatty acids and not synthesized by human being and hence, must be obtained from dietary sources. High level of linoleic acids in the oil reduces the blood cholesterol level and plays an important role in preventing atherosclerosis.^[29] Thus, edible oil with high linoleic acid content is premium oil. According to results of this study, B. juncea had highest linoleic acid among the studied species which can be used for genetic analysis and breeding programs. It is worthy to note that linolenic acid is also an essential fatty acid, however its presence in the oil may causes rancidity and off-flavor.

Correlations within Oil Content and Fatty Acid Compositions

High oil content in Brassica serves as the most important breeding objective. Oil content was positively and significantly correlated to oleic and stearic acids. Also, strong significant and negative correlations were found between oil content with linolenic and erucic acids (Table 5). Oleic and some other fatty acids such as palmitic acid (r = 0.71), stearic acid (r = 0.88), linolenic acid (r = –0.92), and erucic acid (r = –0.92) showed higher correlation coefficients, suggesting that it is in direct association to steps needed for oil synthesis.^[30] B. napus showed positive correlation between palmitic to oleic acid.^[31] The presence of strong and negative correlations between oleic and erucic acids denoted that those genes with contribute to high erucic acid content, function at the expense of desaturation to linoleic and linolenic acids. The relationship between the syntheses of the two fatty acids can be observed in B. napus (accession Okapi) with 0% of erucic acid and about 64% of oleic acid. While, in B. carinata (accession B.C.B-18) the amount of erucic acid reached the maximum among all accessions investigated (45%), whereas, oleic acid had the lowest concentration (about 8%), compared to the other studied accessions. The genetic correlations substantiated phenotypic correlations in the present research. Others have reported a significant negative correlation among oleic acid with erucic and linolenic acids.^[32,^33] The low and insignificant correlation between oleic and linoleic acid was observed. Two separate biosynthetic pathways which are genetically independent are responsible for this result, one which converts oleic acid to linoleic and the other which converts oleic to eicosenoic to erucic acid.^[34] As such, large increases in oleic acid content, due to the genetic absence of erucic acid, did not lead to sharp increases in linoleic acid. The palmitic acid also correlated negatively to linolenic and erucic acids. These results are in line with the biosynthetic pathway of the main fatty acids from oleic acid as many authors^[35,^36] pointed out that erucic acid is formed from oleic acid via chain lengthening process and linoleic and linolenic acids are formed by successive desaturation of oleic acid. Phenotypic correlations between palmitic and stearic acid were small despite the fact that these are synthesized sequentially in the biosynthetic pathway.

TABLE 5 Phenotypic (above diagonal) and genotyping (below diagonal) correlation coefficients of Brassica species for oil content and fatty acid compositions

	1	2	3	4	5	6	7
1- Oil content	1	0.56^n.s	0.76**	0.94**	−0.13^n.s	−0.95**	−0.79**
2- Palmitic	0.55	1	0.54^n.s	0.71**	0.37^n.s	−0.65*	−0.77**
3- Staeric	0.61	0.58	1	0.88**	0.28^n.s	−0.68*	−0.92**
4- Oleic	0.91	0.56	0.84	1	0.06^n.s	−0.92**	−0.92**
5- Linoleic	−0.21	0.59	0.37	0.13	1	0.27^n.s	−0.42^n.s
6- linolenic	−0.92	−0.30	−0.55	−0.87	0.29	1	0.72**
7- Erucic	−0.71	−0.73	−0.89	−0.90	−0.52	0.61	1

CONCLUSION

The considerable genetic variation and high heritability for oil content and fatty acid composition suggested that selection for improving oil content and some of the fatty acid composition might be promising. The findings indicated that wild species exhibited significantly lower average oil content than the cultivated rapeseed. Nevertheless, these species may be a good source of genes to improve some fatty acid composition or other traits of rapeseed. Among wild species, B. rapa and B. oleracea had the highest oil content and high erucic acid that can be used for industrial applications. Furthermore these species are easily crossed to cultivated rapeseed and can be used as a new source of biotic and abiotic stress resistance genes or for incorporating in genetic studies such as re-synthesis B. napus. The results of genotypic and phenotypic correlation were in line with the biosynthetic pathways of the major fatty acids.