Table of Contents
Morales, M.R., D.J. Charles, and J.E. Simon. 1993. New aromatic lemon basil
germplasm. p. 632-635. In: J. Janick and J.E. Simon (eds.), New crops.
Wiley, New York.
New Aromatic Lemon Basil Germplasm*
Mario R. Morales, Denys J. Charles, and James E. Simon
- Table 1
- Table 2
- Table 3
- Fig. 1
- Fig. 2
Basil (Ocimum basilicum L., Lamiaceae) has long been acclaimed for its
diversity as a source of essential oils, its flavor and delicacy as a spice,
and its beauty and fragrance as an ornamental (Simon et al. 1990). Basil is
extensively used by the perfume, pharmacy, and food industries for its natural
aroma and flavor (Darrah 1980; Simon et al. 1984). There are many variants of
basil which exhibit a wide range of leaf color (green to dark purple), flower
and bract color (red, white, lavender, or purple), and which vary in growth
characteristics and aroma making it an increasingly popular culinary and
ornamental herb. Basils are annual plants and, generally, flowering commences
about 80 days after planting in late spring. The flowers as well as the leaves
are highly aromatic.
Most basils are grown as culinary herbs primarily because of their unique
aromas and fragrances, which can be strikingly similar to the aroma of
cinnamon, licorice, lemon as well as the more traditional sweet basil aroma
which is mainly due to a combination of linalool, methyl chavicol, and
1,8-cineole. Basils, which exhibit a lemon aroma (due to the presence of
citral), are commercially available and are characterized by their small
stature, early flowering, small and narrow leaves, and low essential oil and
citral contents. In 1988, we compared three field-grown lemon basil cultivars,
and found that the citral content in the essential oil was 12.6% (Companion
Plants), 14.4% (Lake Valley), and 32.4% (Burpee Seeds). In 1989, we identified
a single robust and tall plant with a very strong and distinct lemon fragrance
within our germplasm collection. This individual plant was found within an
extensive intermated germplasm collection of Ocimum spp. and served as
the parent to derive a new type of lemon basil for the culinary and ornamental
herb market. We were also interested in comparing the effect of steam versus
hydrodistillation on oil yield and composition.
In 1989, an individual plant with strong lemon aroma and a distinct upright
growth habit with larger leaves than previously found on available lemon basil
cultivars was identified in a genetically broadbase germplasm collection of
basil (Ocimum spp.) growing at Lafayette, Indiana (Oakley silt loam
soil). The selected plant was potted and placed in a greenhouse, isolated from
all other basils. Selfed seed (S1) was collected in March, 1990, and sown in
the greenhouse on Apr. 20, 1990. One month later, the 80 plants obtained were
transplanted into the field, eight rows of ten plants each. At full bloom
(July 16), the foliage and flowers of each plant were harvested (from 20 to 25
cm above ground), and immediately dried at 37°C in a forced air dryer for 15
days. Essential oils were extracted by hydrodistillation via clevenger trap
according to Charles and Simon (1990). Oil content was measured volumetrically
(% v/dry wt), and oils stored in Teflon sealed silica vials at 2°C in the
dark. Essential oil composition was determined using a Varian 3700 GC equipped
with FID and a Varian electronic 4270 integrator as reported (Charles and Simon
1990). Identification of citral (= neral and geranial) was verified by the use
of standards and with a Finnigan 4000 GC/MS as described (Charles et al. 1990;
Simon and Quinn 1988).
From among the 80 field-grown plants in 1990, five plants were selected for
further development based on plant type, visual appearance, essential oil
content, aroma, and citral content. These plants were vegetatively propagated
and greenhouse-grown in isolation during the Fall of 1990 and second generation
selfed seed (S2) collected in March 1991. These five lines and remnant seed of
the original plant (check) were field evaluated in a completely randomized
block design with three replications in 1991. Each line was transplanted into
five-row plots, ten plants per row, 46 cm between plants and 91 cm between rows
on May 22, 1991 (Fig. 1). Plant height was estimated by measuring two random
plants from each of the five rows. A relative measure of the leaf size from
each line was estimated by collecting two fully mature leaves from a randomly
selected plant in each of the five rows per plot and measuring the total leaf
area using a LI-COR Model 3100 area meter. From July 9 to 23, when plants where
in full bloom (Fig. 2), the three central rows were harvested in bulk, cutting
the plants at ground level, and all the biomass weighed fresh and then
immediately distilled to collect the essential oils using a 500-liter portable
steam distillation unit (Alkire and Simon 1990) at 0.56 kg/cm2 for 2
h. On July 12, ten plants from the first row of each 5-row plot were
individually harvested, cutting them 20 to 25 cm above ground, dried at 37°C
in a forced air dryer from 15 to 20 days and the oil extracted using 40- to
75-g samples in 2-liter clevenger trap hydrodistillation units ran for 1.25 h.
Oils were stored and analyzed as described earlier. The last row of each 5-row
plot was left for seed collection.
In 1990, plants were first evaluated for visual appearance and aroma. Plants
which had foliar discolorations, exhibited disease symptoms or any other
irregularities were rogued. Variation was high in all growth and oil
characteristics in the segregating lemon basil population in 1990. Mean growth
characteristics were as follows: plant height 55 cm; fresh weight 256 g; dry
weight 31.4 g; oil yield 0.69% (v/dw); and citral content 67.2% of total
essential oil. Five plants (Plant No. 47, 48, 75, 77, and 78) with 76.4 to
78.7% citral and 0.44 to 0.75% (v/dw) essential oil content were selected.
In 1991, significant differences among the five lines (S2) and plants derived
from selfed seed from the original plant (check) were observed for foliage
yield, plant height, days to 50% flowering, uniformity, and essential oil yield
(hydrodistillation) (Table 1, 2). The lines did not vary from the original
plant selection in relative leaf size and citral content as extracted by steam
While citral content in the hydrodistilled oil did not vary among the five
lines, all were significantly higher (average 13%) than the original parent
check (Table 2). On average, the five selected lines of the second generation
plants yielded 53% more oil than the original plant check (via
hydrodistillation) and the plants were significantly taller (Table 1, 2).
While the steam and hydrodistillation methods yielded the same amount of
essential oils (1.1 ml/m2), the citral content in the hydrodistilled
oil was 50% higher than from steam distillation. Citral could have been lost
in the actual physical collection of the oil with the steam distillation unit,
but whether the citral was lost or chemically altered is as yet unknown (Table 2). The correlation for essential oil yield between steam and
hydrodistillation was highly significant (r = 0.74**) whereas, there was no
correlation between the extraction methods for citral content (r = 0.20), due
to the lack of complete citral recovery from steam distillation.
Citral content was about 14% lower in all lines and the check in 1991 compared
to 1990, which we presume was due to the more stressful season with average
high day and night temperatures. The effect of seasonal differences on citral
content is unknown. The original plant (check) flowered about 4 to 7 days
later than the selected lines. Lines 75, 77, and 47 were most uniform (Table 1). Essential oil yield correlated positively with plant height and foliage
fresh weight and negatively with days to 50% flowering (Table 3).
After two cycles of selfing and selection, we identified five uniform lines of
lemon basil with desirable aromatic, horticultural, and ornamental
characteristics. This is the first report of a tall highly aromatic lemon
basil that has potential as an ornamental culinary herb. Plants exhibited a
strong pleasant lemon aroma, and compared to commercially available lemon basil
cultivars, had larger leaf size (similar to sweet basil genotypes), and taller
stature. Both the available cultivars and the new lemon basils described here,
have attractive white flowers (Fig. 2) which continue to bloom as the plants
continue to grow until frost. Each line had a distinct lemon fragrance with a
minimum citral content of 65% in 1991. All the lines were highly aromatic with
essential oil contents of 0.79 to 0.87% (v/dw) in 1991. Each line was highly
vigorous with plants reaching heights of 58 to 65 cm in 1991 (Fig. 1, 2). All
five lines appear superior to the original plant (check), with lines 75, 77,
and 47 the most aromatic, vigorous, and uniform.
- Alkire, B.H. and J.E. Simon. 1990. Construction and design of a portable
steam distillation unit for peppermint and spearmint. In: Proc. 1990 Mint
Industry Research Council (MIRC), Annual MIRC Meeting, Las Vegas, NV. January,
- Charles, D.J. and J.E. Simon. 1990. Comparison of extraction methods for the
rapid determination of essential oil content and composition of basil
(Ocimum spp.). J. Amer. Soc. Hort. Sci. 115:458-462.
- Charles, D.J., J.E. Simon, and K.V. Wood. 1990. Essential oil constituents of
Ocimum micranthum Willd. J. Agr. Food Chem. 38:120-122.
- Darrah, H.H. 1984. The cultivated basils. Buckeye Printing Company,
- Simon, J.E. and J. Quinn. 1988. Characterization of essential oil of parsley.
J. Agr. Food Chem. 36:467-472.
- Simon, J.E., A.F. Chadwick, and L.E. Craker. 1984. Herbs: An indexed
bibliography 1971-1980; the scientific literature on selected herbs, and
aromatic and medicinal plants of the temperate zone. Archon Books, Hamden,
- Simon, J.E., J. Quinn, and R.G. Murray. 1990. Basil: a source of essential
oils, p. 484-489. In: J. Janick and J.E. Simon (eds.). Advances in new crops.
Timber Press, Portland, OR.
*Journal paper no. 13,177, Purdue Univ. Agr. Expt. Sta., West Lafayette, IN
49707-1165. This research was supported in part by grants from the Indiana
Business Modernization and Technology Corporation, Indianapolis, and the Purdue
University Agricultural Experiment Station (Specialty Crops Grant No.
Table 1. Growth and yield characteristics of second generation lemon
basil lines evaluated in 1991.
zBased on harvesting 30 plants; plot size = 12.54 m2.
| ||Foliage yield|
|Lines ||Area fresh wt (kg/plot)z ||Plant dry wt (g/plant) ||Plant height (cm) ||No. days to 50% flowering ||Leaf area (cm2)y ||Uniformity estimatex|
|75 ||25abw ||110a ||62a ||75a ||19.7 ||1.7a|
|77 ||27a ||112a ||65a ||77a ||17.2 ||1.7a|
|47 ||28a ||105ab ||62a ||74a ||18.6 ||1.3a|
|78 ||24ab ||94bc ||58b ||76a ||18.5 ||3.3b|
|48 ||22b ||100ab ||62a ||76a ||17.8 ||2.7b|
|Checkv ||24ab ||81c ||53c ||81b ||19.3 ||5.0c|
|Mean ||25 ||100 ||60 ||77 ||18.5 ||2.6|
|LSD (5%) ||4 ||15 ||3 ||3 ||NSD ||0.9|
|CV ||8 ||9 ||2 ||2 ||9.4 ||19.4|
yBased on 10 leaves/plot.
xPhenotype uniformity, based on visual estimating, 1 = very uniform;
5 = wide plant to plant variation.
wNo significant differences between means with same letter.
vSeed from the original single plant identified in 1989.
Table 2. Effect of the extraction method on the essential oil yield and
citral content of five second-generation sister lemon basil lines and the
parent line evaluated in 1991.
zCitral contents of each line from first generation of selfed seed
were 78.7% (P75), 77.0% (P77), 76.8% (P47), 76.5% (P48), and 76.4% (P78), and
citral content of original plant was 67%, in 1990. Citral content from the
hydrodistilled oil was about 14% lower in 1991 than in 1990.
| ||Extraction method|
| ||Steam distillation ||Hydrodistillation|
| ||Essential oil yield|
|Lines ||Essential oil yield (ml/m2) ||Citral content (% of total oil)z ||(ml/m2) ||(% v/dw) ||Citral content (% of total oil)z|
|75 ||1.5ay ||48 ||1.3a ||0.81a ||65a|
|77 ||1.4ab ||49 ||1.2a ||0.79ab ||68a|
|47 ||1.2ab ||42 ||1.2a ||0.80a ||68a|
|78 ||1.1ab ||45 ||1.2a ||0.87a ||68a|
|48 ||1.0bc ||38 ||1.2a ||0.79ab ||65a|
|Check ||0.6c ||43 ||0.8b ||0.59b ||59b|
|Mean ||1.1 ||44 ||1.1 ||0.77 ||66|
|LSD (5%) ||0.4 ||NSD ||0.3 ||0.20 ||5|
|CV ||19.5 ||14 ||14.1 ||14.80 ||4|
yNo significant differences between means with same letter.
Table 3. Correlation coefficients between five lemon basil traits of
selected lines evaluated in 1991.
zExtracted by steam distillation.
|Trait ||Essential oil yieldz ||Plant height ||Days to 50% flowering ||Leaf area|
|Foliage fresh weight ||0.47* ||0.26 ||-0.18 ||0.02|
|Essential oil yieldz || ||0.72** ||-0.56* ||0.04|
|Plant height || ||-0.54* ||-0.27|
|Days to 50% flowering || ||0.13|
*, **Levels of significance different from zero at probabilities of 0.05 and
Fig. 1. Flowering plants of lemon basil germplasm grown in Central
Fig. 2. Close-up of an individual plant of lemon basil.
Last update September 18, 1997