Industrial Crops and Products 15 (2002) 59–69

Seed yield, yield components, oil content and essential oilcontent and composition of Nigella sati�a L. and Nigella

damascena L.

L. Filippo D’Antuono *, Alessandro Moretti, Antonio F.S. LovatoDepartment of Agro-en�ironmental Sciences and Technologies, Uni�ersity of Bologna, �ia Filippo Re 6,

Bologna and Food Science and Technology Laboratory, Uni�ersity of Bologna, �ia Ra�ennate 1020, Cesena, Italy

Accepted 13 June 2001

Abstract

Nigella sati�a and Nigella damascena are two annual species of the family Ranunculaceae, investigated recently forthe oil, essential oil and other biologically active constituents of their seeds. They are presently used in traditionalmedicine and for culinary preparations in many countries, as ornamentals, and are also considered for their abundantnectar secretion. One accession of N. sati�a and two of N. damascena were compared on three spring sowing datesin northern Italy. Seed yield, yield components, essential oil content and composition were evaluated. Oil content wasalso measured in N. sati�a. Total and seed biomass decreased with delayed sowing, because of a reduction in bothseed number per plant and mean seed weight. Seed number per plant was the more important yield component forboth species. Actual seed yield was lower for N. sati�a, whereas yield potential seemed to be similar for the twospecies. The main constraint to yield potential of N. sati�a seemed to be connected to its short vegetative phase, withconsequently low number of seeds per unit area. The essential oil composition differed markedly in the two species.Monoterpenes were dominant in N. sati�a, with p-cymene and thymol as the main components. The amount ofpharmacologically active thymoquinone was lower than reported in the literature. N. damascena essential oil wasalmost completely composed of sesquiterpenes. Essential oil composition was very stable in N. damascena, butmarkedly affected by sowing date in N. sati�a. Oil yield of N. sati�a decreased with delayed sowing. As a whole, thetwo species had positive agronomic traits, such as short growing cycle, low seed shattering and low susceptibility todiseases. This, together with different possible options for direct utilisation or industrial processing, may determine aninterest in further considering the two species as potential new multi-purpose crops. © 2002 Elsevier Science B.V. Allrights reserved.

Keywords: Black cumin; Love-in-a-mist; Medicinal plants; Multi-purpose crops; Sowing date; Thymoquinone

www.elsevier.com/locate/indcrop

* Corresponding author. Tel.: +39-051-209-1548; fax: +39-051-209-1545.

E-mail address: dantuono@pop.agrsci.unibo.it (L.F. D’An-tuono).

1. Introduction

The genus Nigella, belonging to the family Ra-nunculaceae, is represented by species of Mediter-

0926-6690/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved.

PII: S 0926 -6690 (01 )00096 -6

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ranean–western Asian origin. These are generallyshort-lived annuals, typical of disturbed soils ornatural communities of semi-arid areas, with adominance of therophytes. In the natural forms,flowers are bluish, with a variable number ofsepals, and characterised by the presence of nec-taries. The gynoecium is composed of a variablenumber of multi-ovule carpels, developing into afollicle after pollination, with single fruits par-tially connected to form a capsule-like structure.Seeds, of generally small size (1–5 mg), dark greyor black colour and with corrugated integuments,represent the useful product.

N. sati�a is extensively used in traditionalmedicine, for healing various respiratory and gas-tro-intestinal diseases in all the Islamic countries,from Morocco to Pakistan (Riaz et al., 1996) and,locally, in southern Europe. The composition andproperties of this species have been fairly exten-sively investigated, and the results of the researchhave recently been reviewed (Riaz et al., 1996;Siddiqui and Sharma, 1996; Worthen et al., 1998):whole seeds or their extracts have antidiabetic,antihistaminic, antihypertensive, anti-inflamma-tory, antimicrobial, antitumour, galactagogue andinsect repellent effects. Most properties are mainlyattributed to quinone constituents, of which thy-moquinone is more abundant compound.Quinonic alkaloids are likely to be involved inpharmaceutical properties as well.

Another use of N. sati�a seeds is as seasoningfor foodstuffs like bread and pickles, especiallywidespread among Turkish people.

Nigella damascena is a less explored species. Itsseeds have a mild aromatic flavour, slightly resem-bling that of strawberries, and they have beenused in the past to garnish cakes and biscuits.Presently, petaloid types with dark blue, purplered or whitish sepals are mainly used for orna-mental purposes.

Both N. sati�a and N. damascena seeds containa variable amount of oil, with linolenic generallyrecognised as the more abundant fatty acid; rele-vant amounts of saturated acids such as palmitic,myristic and stearic were found in some cases, aswell as the presence of unusual unsaturated c20acids (Babayan et al., 1978). An unusual characterof Nigella seeds is the very high lipase content and

the consequent high amount of free fatty acids(U� stun et al., 1990; Riaz et al., 1996).

The Nigella species are actively visited by hon-eybees (Ricciardelli D’Albore and Persano Oddo,1981), and N. sati�a is also a component of com-mercial seed mixtures for bee foraging (Engels etal., 1994).

The Nigella species therefore appear to be po-tential multi-purpose crops of possible interest.Agronomic experiments of seed yield have beencarried out in north African and middle easterncountries on N. sati�a. However, apart from apaper dealing with the effect of water supply(Mozzafari et al., 2000), the combined effects ofgrowing factors on yield and essential oil qualityhave not been examined. In addition, only re-search on seed production of N. damascena forornamental purposes has been carried out in tem-perate climates. In the framework of researchprogrammes on minor, wild or semi-domesticatedspecies, the potential of N. sati�a and N. damas-cena seed production, and some quality charactersof the seeds, such as germination, oil content,essential oil content and composition wereevaluated.

2. Materials and methods

One accession of N. sati�a and two of N. dama-scena were compared on three sowing dates(March 3, April 9 and May 7, 1997) at theOzzano experimental farm of the University ofBologna, northern Italy. Seeds of N. sati�a wereobtained from a herbal market in Rabat (Mo-rocco), whereas the N. damascena samples wereobtained from two different commercial firms.The experimental scheme was a three-replication,randomised block split-plot, with sowing dates inthe main plots and plant samples in the sub-plots.Sowing was done by a mechanical plot driller, at20 cm row distance, with a seed amount tuned toa target density of 200 p m−2, taking into accountlaboratory germinability and 50% possible emer-gence failure, because of the apparently low seedvigour. Plot size was 6 m2. No fertilisation, irriga-tion or chemicals were applied. Weeds were con-trolled by hand, when needed.

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Harvesting was done manually by pulling thedry plant out of the soil, and removing the roots.The seeds were separated from the straw bymeans of a lab thresher. Dry matter of seeds andstraw was determined by oven drying a sub-sam-ple until constant weight. The number of plantsper square meter was counted on two replicated1-m rows per plot. The number of seeds per plantwas determined on a sub-sample of 20 plants perplot, separately threshed, and mean seed weightwas determined on 400 seeds per plot.

Seed germinability was determined on paper at20 °C. Seed oil of N. sati�a was extracted from 2g seed samples per plot, finely ground underliquid nitrogen, by means of a Soxtech apparatus.

The methodology for essential oil extractionand analysis are reported in detail elsewhere(Moretti and D’Antuono, 2001). Briefly, essentialoil content was determined gravimetrically, afterwater distillation and extraction in a Likens–Nickerson apparatus. The oil was analysed bymeans of a 3300 Varian gas chromatograph cou-pled with a Finnigan MAT ITD-40 mass spec-trometer under the following conditions: BPX-5fused silica capillary column 30 m×0.25 mm×0.25 �m; carrier gas, helium; injector, 240 °C;detector, 280 °C; temperature programme: from80 °C (2 min) to 150 °C (10 min) at 3 °C/min,then to 240 °C at 10 °C.

All the characters measured were subjected tothe analysis of variance, including the followingeffects: species, sowing date, accession within spe-cies (N. damascena) and the species–sowing dateinteraction. The differences between individualtreatments were assessed by the protected leastsignificant difference (Steel and Torrie, 1980).

Multiple regression and path coefficient analy-sis were used to study the relationships amongseed yield and its components.

The relationships between: (a) vegetativebiomass and the number of seeds per unit area,and: (b) total and seed biomass were analysed bya negative exponential equation of the type:

Y=ASY(1−exp(−X(IE/ASY))),

where: X is the ‘independent’ variable (respec-tively: (a) vegetative biomass or (b) total biomassper unit area); Y is the dependent variable (respec-

tively: (a) number of seeds or (b) seed biomass perunit area); ASY is the asymptotic value of thefunction (respectively: (a) asymptotic number ofseeds or (b) asymptotic seed biomass per unitarea); IE: initial efficiency, approached by the firstderivative of the function for X�0. For the rela-tionship (a), the parameter IE had the meaning ofthe maximum value of the so-called reproductiveefficiency (Spitters, 1989), expressed as number ofseeds produced per unit vegetative biomass. Forthe relationship (b), IE represents the upper limitof the harvest index.

The analytical data of essential oil compositionwere subjected to principal component analysis, inorder to extract factors accounting for much ofthe variability of the original data set, and betterexplaining the effects of the experimental treat-ments. The factors with eigenvalues higher than 1were retained for the discussion of the results(Hair et al., 1998).

All the statistical analyses were carried out bymeans of the SYSTAT 8.0 package (Wilkinson,1998).

3. Results

3.1. Agronomic and biometric characters

Most agronomic and biometric characters wereaffected by the experimental factors: species, sow-ing date and their interaction (Table 1), whereasno differences were detected between the two ac-cessions of N. damascena. Seed yield was higherfor N. damascena and decreased in late sowings.However, the difference between the two specieswas mainly due to the highest yield of N. damas-cena in the first sowing. Straw biomass had asimilar pattern with a more pronounced advan-tage of N. damascena and relatively higher de-crease than that observed in seed production, withthe delay of sowing. These facts are also wellrepresented by the harvest index, that was higherfor N. sati�a and showed an increasing trend inlate sowings, more evident for N. damascena ; infact, the second sowing of N. sati�a had a bettervegetative growth than the first one with a signifi-cantly lower harvest index.

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Table 1Effect of the experimental treatments on yield and seed quality charactersa

Dry biomass Yield componentsHarvest index Seed characters(kg ha−1) (kg kg−1)

Seed Straw Total Seed weight Plant densitySeed density Germinability Oil Essential oil(m−2) (g kg−1) (g kg−1)(mg seed−1) (%)

(n m−2) (n plant−1)

Species786 1444 2230 0.361 3.0N. sati�a 26,057 187 179 75.6 183.3 3.9

N. damascena 1007 2914 3921 0.272 2.1 47,488 348 187 90.5 – 3.9134 624 732 0.020 0.1 5410L.S.D. (P=0.05) 56 ns 3.9 – ns

Sowing date1337 3814 5151 0.286 2.56 March (s1) 56,240 508 116 89.9 191.0 3.8

979 2426 3404 0.289 2.4 42,155 276 154 87.7 227.4 3.89 April (s2)486 1032 1518 0.329 2.37 May (s3) 22,637 100 282 78.9 131.4 4.2

L.S.D. (P=0.05) 154 721 846 0.024 0.1 6246 65 87 4.5 87.5 ns

Species–sowingN. sati�a

1018 1706 2723 0.377 3.0s1 33,446 274 129 85.7 – 5.0937 1981 2917 0.320 3.1s2 30,448 234 130 83.0 – 2.8

s3 404 645 1048 0.386 2.8 14,276 53 278 58.0 – 4.1N. damascenas1 1496 4868 6365 0.240 2.2 67,638 625 110 92.0 – 3.2

999 2648 3647 0.274 2.1 48,008 297s2 166 90.0 – 4.3527 1226 1752 0.301 2.0s3 26,817 124 284 89.4 – 4.2

L.S.D. (P=0.05) 231 1081 1269 0.035 ns 9370 97 ns 6.8 – 0.8

a Least significant differences (L.S.D.) reported only for characters significantly different according to the analysis of variance; ns: not significant.

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Among yield components plant density waslower than the target value in the first two sow-ings and higher in the third, because of betteremergence without, anyway, any positive influ-ence on seed production. The other yield compo-nents (seed number per plant and per unit area,mean seed weight), decreased, on average, withthe delay of sowing. Seed number was signifi-cantly higher for N. damascena and mean seedweight for N. sati�a. All characters were howeveralso affected by the species–sowing date interac-tion. In fact, the decreasing pattern of the threecomponents was regular for N. damascena,whereas, for N. sati�a, sowing two deviated fromthis trend, with seed number not significantlydifferent and mean seed weight higher than sow-ing one.

Path analysis (Table 2) explains the relation-ships between seed yield and its components. Onboth species, seed yield was linked to number ofseeds per plant and mean seed weight by positivesimple correlations, and to number of plants perunit area by negative correlation. However, multi-ple regression demonstrates that all three compo-nents had positive direct effects on yield (�coefficients), as would be expected, although thecoefficients of plants per square meter were notstatistically significant. The negative simple corre-lation of plants per square meter to yield was theresult of its modest positive direct effect andrather strong indirect negative effect, via the sig-nificant negative correlation to both the otheryield components. On the contrary, the number ofseeds per plant and mean seed weight were mutu-

ally positively correlated for both species, com-pensating the indirect negative effect of theircorrelation to plant density.

For both species, the relative effect of the num-ber of seeds per plant on seed yield was higherthan that of mean seed weight, as indicated by thehigher path coefficients (�). Taking into accountthe similar value of the correlation coefficients,this fact depended on the strong positive indirecteffect of mean seed weight on yield, via its posi-tive correlation to seed number per plant.

The absolute values of the multiple regressioncoefficients indicate that the more critical determi-nants of seed yield were seed number per unit areaand mean seed weight for N. sati�a and N. dama-scena, respectively. This is consistent with theabove-mentioned lower number of seeds andhigher mean seed weight of N. sati�a.

Further explanations of the yield strategy of thetwo species can be deduced from Figs. 1 and 2.The amount of vegetative biomass has often beenrelated to seed yield potential: in fact, during thevegetative phase, seed number and thus total sinkcapacity is determined (Spiertz and van Keulen,1980). The asymptotic values of seed number persquare meter (parameter ASY), as a function ofvegetative biomass (Fig. 1) are very different forthe two species, with higher values for N. damas-cena, whereas the initial reproductive efficiencies(IE) are comparable. The examined range of vege-tative biomass is also substantially different. Thisindicates that the amount of resources required toproduce one potential seed is the same, whereasthe different potential values of final seed number

Fig. 1. Relationship between the yield of vegetative dry biomass and number of seeds per square meter, interpolated by means ofthe equation: Y=ASY(1−exp(−X(IE/ASY))). ASY, asymptotic seed density (n m−2); IE, initial reproductive efficiency (n seedsg−1 vegetative biomass).

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Table 2Results of path analysis carried out regressing seed yield on yield components for the two Nigella species:*

SimpleYield components (yc) Correlation between independentMultiple regression Effect on grain yieldcorrelation (r) coefficients (b) variables

direct (�: path indirect via yc1 yc2 yc3coefficients)

yc1 yc2 yc3

N. sati�a (r2=0.931a)−0.748b −1.54�1.01 0.412 ns – −0.863 −0.298(yc1): plants m−2 1 −0.897a −0.632c

0.889a 2.77�0.78 0.962a −0.370(yc2): seeds plant−1 – 0.296 −0.897a 1 0.629c

0.815a 997�327 0.471b −0.261 0.605(yc3): mean seed weight – −0.632c 0.629c 1

N. damascena (r2=0.899a)−0.527b(yc1): plants m−2 −0.42�0.40 0.108 ns – −0.468 −0.166 1 −0.642a −0.525b

0.929a 1.44�0.32 0.729a −0.069(yc2): seeds plant−1 – 0.269 −0.642a 1 0.849a

0.879a 1217�562(yc3): mean seed weight 0.317b −0.057 0.619 – −0.525b 0.849a 1

* number of plants per square meter (yc1), number of seeds per plant (yc2) and mean seed weight (yc3).a P�0.01,b P�0.05,c P�0.10.

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Fig. 2. Relationship between total and seed biomass, interpolated by means of the equation: Y=ASY(1−exp(−X(IE/ASY))).ASY, asymptotic seed yield (kg ha−1); IE, initial harvest index (kg seed kg−1 total biomass)

Table 3Dates of the main phenological stages of the two Nigella species

Flower bud Flowering Harvest

Beginning End

Sowing: March 03May 14N. sati�a May 21 June 17 July 19

June 11 July 09N. damascena July 27June 04

Sowing: April 09N. sati�a June 01 June 07 July 02 July 25N. damascena June 13 June 20 July 16 August 01

Sowing: May 07N. sati�a June 13 June 18 July 11 August 01

July 01N. damascena July 23June 22 August 06

is connected to the lower vegetative growth of N.sati�a.

Seed yield potential, indeed, did not seem todiffer between the two species, as indicated by thevalues of the asymptotic seed yield (parameterASY) of Fig. 2. The lower actual seed yield of N.sati�a was therefore due to its lower total biomassrange, mainly determined, as previously men-tioned, by its lower vegetative growth. The higherinitial harvest index (parameter IE) is consistentwith that observed in the experimental data andmay indicate a better adaptation of N. sati�a tolow potential environments for vegetative growth.

The major yield limiting factor for N. sati�aseemed therefore to be a low sink potential, deter-mined by reduced assimilate supply during thepre-anthesis phase. From Table 3 it appears thatthis species was rather earlier than N. damascena.

Its lower vegetative biomass and number of early-determined yield components seem therefore to beconnected to the shorter duration of its vegetativecycle.

For N. damascena, the constraints to yield areinstead connected to its low harvest index, mainlydetermined by low mean seed weight.

3.2. Seed quality and composition

Seed germination was higher for N. damascenaand decreased with delayed sowing, particularly inN. sati�a, for which it reached rather low values inthe third sowing.

Oil content of N. sati�a seeds increased fromthe first to the second sowing, then dropped tolower values in the third, with lower averagecontent than those reported in the literature

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(U� stun et al., 1990; Riaz et al., 1996; Saeed et al.,1996)

Essential oil content of both species was consis-tent with that reported elsewhere (Riaz et al.,1996; Mozzafari et al., 2000), and was not af-fected by the average effect of species and sowingdate. Also in this case, however, sowing two of N.sati�a behaved differently, giving significantlylower values than the other two sowings.

Essential oil composition and the identificationkey of single components are reported in Tables 4and 5, respectively. The oil composition of thetwo species was completely different, as illustratedand discussed elsewhere (Moretti and D’Antuono,2001). Significant species–sowing date interac-tions were found for all oil components. In fact,the essential oil composition of N. damascena wasvery stable, with no significant differences in anyindividual components due to sowing date. On the

contrary, oil composition of N. sati�a was heavilyaffected by sowing date, with the second sowingbehaving substantially differently to the othertwo. In fact, the lighter oil components (c1–c7)were absent, and c8 and c10 substantially lower,whereas the amount of most of the heavier com-ponents (c11–c18) was higher in the second sow-ing. The third sowing had an oil compositionqualitatively more similar to the first one, al-though being differentiated by the generally loweramount of the lighter components, up to c8, thehigher amounts of c5, c10, c13, c14 and c15, andthe presence of some high weight sesquiterpenes(c19, c20 and c22), almost absent in the other twosowings of N. sati�a. An exhaustive interpretationof these variations is not possible on the basis ofthe results of this research, even if the oppositepattern of thymol (c15) and p-cymene (c8) iseasily explainable given that the second is a pre-

Table 4Identification key of the essential oil components and loadings of individual components to the first three factors (PCs) extractedby means of principal component analysisa

Essential oil components Loadings to

PC2PC1NameKey PC3

c1 0.550.78 −0.28Thujene�-Pinene 0.78c2 0.78 −0.26

−0.10Sabinene 0.82 0.54c30.55 −0.13�-Pinenec4 0.82

0.82Myrcene 0.47 0.14c5c6 0.150.510.85�-Terpinene

0.460.65 −0.31o-Cymenec7−0.05p-Cymene 0.97 0.21c8

Limonene 0.79c9 0.49 0.19c10 �-Terpinene 0.73 0.35 0.51

−0.03−0.550.83c11 trans sabinene hydrateThujol 0.83c12 −0.53 −0.09

c13 Thymoquinone 0.87 −0.45 0.13−0.39 0.11Myrtenolc14 0.91

Thymol 0.75c15 −0.66 0.06c16 �-Bourbonene+�-caryophyllene −0.94 0.18 −0.01c17 �-Elemene −0.98 0.09 −0.05

Longifolene 0.85c18 −0.46 0.01�-Selinene 0.160.22−0.76c19�-Selinene −0.42c20 0.25 0.70Germacrene A −0.93c21 0.16 −0.07

−0.97c22 0.027-Epi-selinene 0.20

66.7 8.3Variance explained by PCs (%) 17.7

a Reference value of the correlation coefficient at P=0.05: 0.36.

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Table 5Effect of the experimental treatments on essential oil composition of the two Nigella species. See Table 4 for component identificationa

Essential oil components (% chromatogram area)

c1 c2 c3 c4 c5 c6 c7 c8 c9 c10 c11 c12 c13 c14 c15 c16 c17 c18 c19 c20 c21 c22

Species3.27 0.70 0.53 1.12 0.29 0.64 3.26 33.75 1.13 2.40 1.05N. sati�a 7.43 3.80 2.44 26.78 0.00 5.47 3.11 0.37 2.17 0.00 0.28

N. damascena 0.00 0.00 0.00 0.00 0.02 0.00 0.00 0.00 0.04 0.00 0.00 0.07 0.08 0.00 0.03 2.10 73.24 0.00 2.68 4.75 10.45 6.540.04 0.04L.S.D. (P=0.05) 0.05 0.06 0.06 0.05 1.44 1.36 0.24 0.55 0.04 0.08 0.24 0.33 0.69 0.30 2.96 0.38 0.65 1.50 1.54 0.45

Sowing date2.44 0.52 0.35 0.74 0.03 0.34 2.43 16.01 0.56 0.81 0.26 1.94 0.86 0.62 4.33 1.41 48.93 0.82 2.30 2.29 7.57 4.436 March (s1)0.00 0.00 0.00 0.00 0.00 0.00 0.00 6.27 0.05 0.07 0.529 April (s2) 3.87 1.80 1.01 14.99 1.40 52.48 1.42 1.60 3.56 6.76 4.21

7 May (s3) 0.83 0.18 0.18 0.37 0.29 0.30 0.83 11.49 0.60 1.52 0.27 1.75 1.30 0.81 7.51 1.38 50.55 0.87 1.84 5.82 6.58 4.730.05 0.05 0.05 0.07 0.07 0.05 1.66 1.57 0.27 0.64 0.05 0.09 0.28 0.38 0.79L.S.D. (P=0.05) ns 3.42 0.44 ns 1.73 ns ns

Species–sowingN. sati�a

7.32 1.56 1.05 2.23 0.00 1.03 7.29 48.00 1.68 2.44 0.76s1 5.82 2.58 1.85 12.89 0.00 0.93 2.46 0.12 0.00 0.00 0.000.00 0.00 0.00 0.00 0.00 0.00 0.00 18.80 0.00 0.20 1.57s2 11.23 4.93 3.03 44.98 0.00 11.00 4.26 0.00 0.00 0.00 0.00

s3 2.48 0.55 0.55 1.12 0.88 0.91 2.49 34.46 1.71 4.57 0.81 5.24 3.89 2.43 22.48 0.00 4.49 2.61 0.98 6.52 0.00 0.84

N. damascena0.00 0.00 0.00 0.00 0.05 0.00 0.00 0.04 0.01 0.00 0.01s1 0.01 0.01 0.00 0.06 1.78 74.51 0.00 2.74 3.44 11.16 6.17

s2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.08 0.00 0.00 0.19 0.23 0.00 0.00 2.11 73.22 0.00 2.39 5.34 10.13 6.31s3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.07 0.00 0.00 0.00 0.00 0.00 0.01 2.16 72.75 0.00 2.95 5.91 9.60 6.55

0.07 0.07 0.08 0.10 0.11 0.08 2.49 2.35 0.41 0.95 0.08 0.13L.S.D. (P=0.05) 0.42 0.58 1.19 ns 5.13 0.66 ns 2.60 ns 0.78

a Least significant differences (L.S.D.) reported only for characters significantly different according to the analysis of variance; ns: not significant.

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Fig. 3. Layout of the Nigella samples on the plane of the first three principal components (PC1, PC2, PC3) extracted from the dataof volatile oil composition. � sowing 1, � sowing 2, � sowing 3.

cursor of the biosynthesis of thymol (Croteau,1986). The amount of thymoquinone, althoughvery low, was correlated to that of thymol, fromwhich this compound derives by oxidation (Mar-tins et al., 1999).

A summary of the information contained in theessential oil analysis was obtained by principalcomponent analysis. The two species (Fig. 3) arewell separated by the first principal component,whereas the second and the third discriminatesowing dates of N. sati�a. PC1 had high loadings(Table 4) to almost all the oil components, withpositive values to the lighter ones and c18 (longi-folene), typical of N. sati�a, and negative to thehigher weight components, typical of N. damas-cena. It is therefore interpreted as a generic factor,connected to the differences between species. Thesecond component had positive loadings to mostoil components absent in the second sowing of N.sati�a, and negative to those present in higheramounts in this sowing. It is therefore inter-pretable as a factor connected to the particularconditions that influenced oil composition of thesecond sowing. The third factor had high positiveloadings with some components peculiar to thethird sowing of N. sati�a that is indeed wellseparated from the other two on the third compo-nent axis.

4. Conclusions

Both species of Nigella revealed positive agro-nomic traits, such as fairly short growing cycle,

good seed retention at harvest time, apparent lowsusceptibility to diseases. In this experiment, seedyields of the earliest sowing were rather promis-ing, also given the fact that there was no technicalinput. The improvement of yield potential alsoseemed achievable through a better harvest indexfor N. damascena, and a higher vegetativebiomass production, connected to a longer dura-tion of the vegetative phase, for N. sati�a. Bothgoals could be pursued through a more accurategermplasm exploration and evaluation. N. sati�ashowed higher variability of yield strategy andessential oil composition in relation to differentenvironmental conditions that may affect the rela-tive amount of the more pharmacologically rele-vant compounds.

With respect to potential uses, neither oil yieldnor fatty acid composition are presently competi-tive with those of more conventional and better-established crops. However, especially N. sati�amay represent a useful source of pharmaceuticals.In this respect, it should be noted that bioactivesubstances, such as thymoquinone and relatedcompounds are found in different sources: the rawsolvent or pressure extracted fixed oil, the crudeseed extract and the essential oil obtained byvapour or hydrodistillation, from which they canbe separated by appropriate selective extractionmethods (Canonica et al., 1963; Riaz et al., 1996;Ghosheh et al., 1999). Therefore, the options forseed processing can vary depending on technicaland economic availability, and the range of mainand by-products may vary accordingly.

L.F. D ’Antuono et al. / Industrial Crops and Products 15 (2002) 59–69 69

This fact, together with the other possible utili-sations and favourable agronomic traits, suggeststhat N. sati�a and N. damascena deserve furtherconsideration and investigation as potential newmulti-purpose crops for industrial uses, seed pro-duction, ornamental and environmental purposes.

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