Fernando D. Goffman

CHEMOTAXONOMIC SIGNIFICANCE OF FATTY ACIDS AND TOCOPHEROLS IN BORAGINACEAE

A collection of 45 accessions (36 species, 20 genera) of the family Boraginaceae was evaluated for oil content, fatty acid composition, tocopherol content and composition. All the accessions contained γ-linolenic acid, the lowest content (0.7%) being found in Cerinthe major L. and the highest (24.4%) in Borago officinalis L. Three tocopherol profiles were characterized by the extremes of more than 90% of α-, δ- and γ-tocopherol, respectively. Fatty acids and tocopherols were suggested to have potential chemotaxonomic value in this family.

Variability for the fatty acid composition of the seed oil in a germplasm collection of the genus Brassica

A germplasm collection consisting of 1475 entries from 21 species of Brassica, including 36 lower taxa, was evaluated for the fatty acid composition of the seed oil. A total of 358 entries representing the taxonomic variability in the collection were selected and analysed by gas-liquid chromatography (GLC). The remaining 1117 entries were analysed by near-infrared reflectance spectroscopy (NIRS), after developing multi-species calibration equations. The results demonstrated that NIRS is an effective technique to assess variability for oleic, linoleic, linolenic and erucic acid in intact-seed samples of multiple Brassica species, provided that calibration equations be developed from sets containing large taxonomic and chemical variability. Some fatty acid ratios were used to estimate the efficiency of the different biosynthetic pathways. Two well-defined patterns were observed. The first one was characterised by high elongation efficiency and accumulation of high levels of erucic acid. The highest erucic acid content (>55% of the total fatty acids) was found in the cultivated species B. napus L., B. oleracea L., and B. rapa L., and in the wild species B. incana Tenore, B. rupestris Raf., and B. villosa Bivona-Bernardi, the three latter belonging to the B. oleracea group (n=9). The second pattern was characterised by high desaturation efficiency, resulting in the accumulation of high levels of the polyunsaturated linoleic and linolenic acid (up to more than 55%). The highest levels of these fatty acids were found in samples of B. elongata Ehrh., especially of the var. integrifolia Boiss. The utility of the reported variability for plant breeding is discussed.

Chemotaxonomic value of tocopherols in Brassicaceae

The significance of tocopherols as chemotaxonomic markers and their relationship withoil content and fatty acid profile was investigated in a collection of 91 species of the familyBrassicaceae. Total tocopherols content ranged from 68 mg kg−1 oil in Diplotaxis viminea to2479 mg kg−1 oil in Schivereckia doerfleri. The collection also showed wide variability fortocopherol composition. The average tocopherol profile consisted of 65.4% g-, 28.7% a-, 5.1%d- and 0.8% β-tocopherol. Individual tocopherols were found to have great taxonomic value inthe Brassicaceae.

Tocopherol, plastochromanol and fatty acid patterns in the genusLinum

The fatty acid composition of the seed oil has been used as a criterion in searching for a rational infrageneric classification ofLinum L.. The objective of the present study was to evaluate the taxonomic potential of other seed traits such as tocopherols and plastochromanol-8 in this genus. The results revealed that, in addition to fatty acids, tocopherols and plastochromanol-8 possess an important chemotaxonomic value for the genusLinum. Sect.Linum and sect.Syllinum Griseb. clearly differed from each other for the three types of compounds. Sect.Linum was characterized by the presence of plastochromanol-8, a high concentration of linolenic acid, and an intermediate or low concentration of alpha-tocopherol. Contrarily, sect.Syllinum lacked plastochromanol-8 and contained a low concentration of linolenic acid and a high concentration of alpha-tocopherol. The three species evaluated of the sectionLinastrum (Planch.) Bentham showed no common pattern, questioning their classification within the same section.

Genetic variation of tocopherol content in a germplasm collection of Brassica napus L.

The genetic variation for tocopherol contents was investigated in a very divergent collection of 87 winter rapeseed genotypes grown in the greenhouse and in two years in the field. Genotypic and environmental effects were highly significant for alpha-, gamma- and total tocopherol contents and the alpha-/gamma-tocopherol ratio. Field and greenhouse environments differed significantly (p < 0.001) for tocopherol traits, with greenhouse means up to 19% higher than field means. Alpha-tocopherol content ranged from 63 to157 mg kg-1 seed, gamma-tocopherol content from 114 to 211 mg kg-1 seed, total tocopherol content from 182 to367 mg kg-1 seed, and the alpha-/gamma-tocopherol contents ratio from0.36 to 1.23. The resynthesized lines often have a remarkably low alpha-tocopherol content and consequently a low alpha-/gamma-tocopherol contents ratio. The lines with altered fatty acid composition displayed the highest variation for both tocopherol content and composition. No significant differences were observed among groups with different seed quality types [00], [0+] and [++]. Total tocopherol content was not correlated with the alpha-/gamma-tocopherol ratio, indicating that total tocopherol content is independent from tocopherol composition. Alpha- and gamma-tocopherol contents were also not correlated. Gamma-tocopherol contents showed a significant positive correlation with oil content (r = 0.34**).

Quantitative determination of tocopherols in single seeds of rapeseed (Brassica napus L.)

A high-performance liquid chromatography (HPLC) method was developed to determine tocopherols in single seeds of oilseed rape (Brassica napus L.). Single seeds were extracted with isooctane, centrifuged, and the overlayer extract injected into the HPLC instrument without further purification. Separation was performed on a diol-column (250 mm × 3 mm I.D.) using a mobile phase consisting of 94% isooctane and 6% tert-butyl methyl ether. Quantification of individual tocopherols was done by fluorescence detection and with β-tocopherol as internal standard. The standard error (SE) of the present method for total tocopherol content, as determined with 30 ground samples of Samourai (mean = 304 mg kg -1 dry seed) and 20 ground samples of Lirabon (mean = 350 mg kg -1 dry seed), was 9.5 mg tocopherol/kg dry seed. The SEs of the method for the determination of α- and γ-tocopherol percentages were 1.2% and 1.3%, respectively. The low SE values indicate that the method can be effectively used to detect small differences for tocopherol content and composition in studies requiring the analysis of reduced amounts of plant material. In particular, the comparison between the SE of the method and the SD of single seeds within individual plants of Samourai (36.8 mg kg -1 dry seed) and Lirabon (37.6 mg kg -1 dry seed) shows the potential of the present method for the detection of the tocopherol content within plant differences.

Fatty acids and tocochromanols in seeds of Orobanche

The evaluation of tocochromanols (tocopherols and tocotrienols) in 49 accessions from 21 Orobanche species revealed three well separated groups. The first one, characterized by high gamma-tocotrienol content, included all the accessions of sect. Orobanche. The second one, exhibiting high gamma-tocopherol content, comprised the accessions of O. arenaria Borkh. and O. purpurea Jacq. (sect. Trionychon Wallr.). All the other accessions of this section presented high delta-tocopherol content. Differences for tocochromanol derivatives within sect. Trionychon were paralleled by differences in the fatty acid profile, with the high delta-tocopherol class having also a higher oleic to linoleic acid ratio.