COMPARING THE GROWTH AND FLOWERING OF SELECTED BASIL (OCIMUM BASILICUM L.) VARIETIES

Investigations carried out in 2005-2006 related to the growth, fl owering, and yielding of selected basil (Ocimum basilicum L.) varieties. The most important biometric traits, number of days from sowing till fl owering, size of fresh and air-dried herb weight, and essential oil content in dried material, were determined. Great morphological and developmental as well as chemical composition differentiation was found for studied basil varieties. Plants of ‘Sweet’ cv. were characterized by the largest height (53.4 cm) and side shoot number (16), ‘Lemon’ – by the largest plant diameter (42.3 cm). The number of days till fl owering depended on weather conditions and the variety, and it amounted from 44 to 126. Basil fl owers were white, pink, and violet. Herb yield depended on the variety and growth conditions. Differences in the amount and yield of essential oil from basil were also recorded. The largest amounts of oil (1.55%) were accumulated by ‘Bush’ cv.


INTRODUCTION
The genus Ocimum is characterized by great species diversity in terms of morphological traits and chemical composition.At present, basil (Ocimum basilicum L.) is widely cultivated in tropical and Mediterranean countries.Green and aromatic leaved varieties are mainly cultivated.Herb and essential oil that has anti-depressive, anti-microbial, and anti-oxidative properties is raw material (M u r a l i d h a r a n and D h a n a n j a y a n , 2004).
Basil is an open and insect pollinated plant.It blooms since June till September and its fl owers secrete signifi cant amounts of nectar (J a r o n i e w s k i , 1998, N u r z y ń s k a -Wi e r d a k , 2000).Basil fl owers are grouped in 6-10-element sets in pseudo-verticils at the shoot top forming pseudo-spikes.The corolla is white, pale-pink or violet.Buds open during the whole day with higher intensity just before noon.Because basil produces fl owers with a short corolla tube, it is an easily accessible nectar source for insects.Mainly honey-bee, solitary-bee and bumble-bee are insects that visit and pollinate basil plants (B o ż e k , 2000; C h w i l , 2003).
The cultivation of basil for fresh or dried leaves and as a decorative plant is particularly common in North America.S i m o n et al. (1999) reported that over 40 basil varieties can be found on American market.In Poland, only two basil varieties are registered (S e i d l e r -Ł o ż y k o w s k a and K a ź m i e r c z a k , 2005), but seeding material is not available.
The present study aims at comparing the growth, fl owering, and essential oil content in raw basil of several English varieties cultivated under climatic conditions of south-eastern Poland.

MATERIALS AND METHODS
The studies were carried out in The Experimental Farm Felin (Agricultural University of Lublin) in 2005-2006. Basil of 'New Guinea', 'Lemon', 'Sweet', 'Napoletano', 'Bush', 'Purple Ruffl es', var. piperita, andvar.lactucoefolium varieties was cultivated from seedlings produced in a heated greenhouse.Seeding material originated from: Chilterns Seeds, Sutton Seeds (cultivated varieties), and from the Botanical Garden of Maria Curie-Skłodowska University in Lublin (botanical varieties).Basil seeds were sown at the beginning of April, and seedlings were planted about May 20 th in 50 × 30 cm spacing.The experiment was carried out by means of the split-plot method in four replications, planting 20 plants in each replication.Observations of 24 randomly selected plants of each variety relating to fl owering dates and intensity were performed during the vegetation period.In general, there were favorable weather conditions, namely in 2005, while at the end of May 2006, the temperature decreased to 5-6°C for short time.Moreover, during the basil vegetation period of 2006, the precipitation total was much lower than in 2005, similarly as temperatures at the end of May and the beginning of July.
Harvest was made at the beginning of basil fl owering by cutting the above-ground part just over the lignifi ed stem fragment.The evaluation of basil growth, leaves number, and yield of fresh herb was also made that time.The raw material was dried under natural conditions, in a dry, dark and ventilated room.Yield of air--dried herb was estimated and then essential oil content was determined in accordance to Polish Pharmacopoeia VI (2002).The achieved results were statistically processed by means of variance analysis for double classifi cation at the signifi cance level of α = 0.05.

RESULTS
Signifi cant differentiation was found in the investigated basil traits relating to the plant's height and diameter, the number of main shoots as well as the length and width of leaf blade, (Tab. 1 and 2).The highest plants (53.4 cm) with the largest number of main shoots (16.0) were produced by 'Sweet', whereas 'Lemon' was characterized by the largest diameter (42.3 cm).Basil leaves were light green ('Lemon'), through green (majority of varieties) to purple ('Purple Ruffl es').'Napoletano' produced the signifi cantly largest and 'Bush' signifi cantly smallest leaves as compared to other varieties.
The studied basil varieties signifi cantly differed in the fl owering rate, number and length of infl orescences, number of verticils in the main infl orescence as well as fl ower color (Tab.3).Plants of 'Bush' variety fl owered earliest (55 days after sowing), 'Purple Ruffl es' latest (after 87 days).The largest number of fl owers was recorded in 'Bush', the largest number of verticils and the longest infl orescences in 'Lemon'.A strong dependence between the earliness of basil fl owering and weather conditions during cultivation was observed, namely for 'Sweet' and 'Purple Ruffl es', the plants which fl owered two times earlier in a year with unfavorable thermal conditions.As regards the fl owering date, the varieties 'Bush' and lactucoefolium can be considered as less sensitive to weather conditions during cultivation.The white color of fl owers dominated, and only the plants of 'New Guinea' produced pink, and 'Purple Ruffl es' light-purple fl owers.
Basil plant weight as well as yield of fresh and air-dried herb signifi cantly depended on a variety and weather conditions (Tab.4).'Sweet' was characterized by the highest, and 'New Guinea' by the lowest mean plant weight and herb yield.Basil cultivated under favorable weather conditions was distinguished by signifi cantly higher weight and yield as compared to those cultivated under worse conditions.
Herb of the studied basil varieties contained from 0.78% (lactucoefolium) to 1.55% ('Bush') of essential oils, on average (Tab.5).It was found that basil plants accumulated signifi cantly more essential oils under less favorable thermal conditions as opposite to more optimum ones.The most apparent differences in essential oil due to weather conditions occurred in basil botanical varieties, the least -in 'Lemon'.The mean effi ciency of oil was from 0.20 to 0.37g per plant, depending on the variety.Essential oil made from basil herb was distinguished by spice-balsamic, liquor-anise, anise and lemon aroma, which also depended on the variety.Regardless of the main aroma component, basil oil had a very strong and durable scent.

DISCUSSION
Basil is considered to be a genus with considerable morphological, chemical, and developmental diversity, and the majority of cultivated varieties belong to the species Ocimum basilicum L. Basil varieties classifi cation is mainly based on the type of growth, leaf size and structure; however, its taxonomy is achieved by the presence of many botanical varieties, cultivated varieties, and chemotypes that signifi cantly differ in their morphological traits (G r a y e r et al. 1996; S i m o n et al. 1999; B r e m n e r, 1999).A system taking into account also the quantitative and qualitative composition of essential oils may be some kind of help (S i m o n et al., 1999).Results of the present investigations confi rm great morphological and developmental variability of basil, as well as its sensitivity to unfavorable weather conditions.
The studied basil was characterized by abundant fl owering, and depending on the variety, plants fl owered from the beginning of June until mid-July.Intensive visits of insects, namely honey-bees and bumble-bees described as visiting and pollinating Lamiaceae plants fl owers, were observed before noon (B o ż e k , 2000; 2002; 2003).B o ż e k (2003) reported that lavender, hyssop, and peppermint plants reacted in a similar way to varied weather conditions; higher temperatures and better insolation accelerated the fl owering date and made the fl owering duration shorter.Other dependencies were recorded in the case of the studied basil varieties.Worse thermal conditions affected earlier plant fl owering for all the investigated basil varieties.However, much smaller differences in the number of days till the start of fl owering were observed under these unfavorable weather conditions.
Amounts of essential oil accumulated by basil plants were in a strict association with the conditions in which they were cultivated.M a r o t t i et al. (1996) reported that the content of essential oil in herb of Italian basil varieties was from 0.3 to 0.7%.A set of 36 basil forms originating from the whole world collected by O s i ń s k a and S u c h o r s k a (1996) was also characterized by a similar oil concentration (0.3% to 0.8%).Basil plants cultivated in middle Africa contained from 0.02% to 2.1% of essential oil (Z o l l o et al., 2006).The varieties investigated in the present study were distinguished by varied essential oil amounts that were, depending on the variety, from 0.35% to 1.95%.Regardless of the weather conditions, 'Bush' contained the highest content of oil (1.55%), which was confi rmed by other authors (Ö z c a n and C h a l c h a t , 2002, Z o l l o et al. 2006).

CONCLUSIONS
1.The studied basil varieties differed from one another in their morphological and developmental traits.Different leaf and fl ower colors make them suitable for decorative purposes.From this point of view, 'Bush' (fi ne green leaves, dense spherical conformation) and 'purpurascens' (purple leaves and pale-purple fl owers) seem to be very interesting.
2. Basil fl owers, depending on the variety, are white, pink or pale-purple.The number of infl orescences on a plant is from 19.5 to 52.6, on average, for the studied varieties.'Bush' plants fl owered earliest, and 'Purple Ruffl es' latest.
3. Basil fl owering depended on weather conditions.Accelerated transition from vegetative to generative stage may be a result of low temperatures at the beginning of plant growth.
4. The weight of basil plants along with the yield of fresh and air-dried herb signifi cantly depended on the variety and weather conditions.'Sweet' was characterized by the highest, and 'New Guinea' the lowest mean plant weight and herb yield. 5. Herb of the investigated basil varieties contained from 0.78% (lactucoefolium) to 1.55% ('Bush') of essential oil.Basil accumulated signifi cantly more essential oil during less favorable thermal conditions as compared to more optimum ones.The greatest differences in oil amounts due to weather conditions occurred for basil botanical varieties, the least -for 'Lemon'.

Table 1
Characteristics of chosen growth features of studied basil cultivars.

Table 3
Characteristics of basil fl owering.