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Valtcho D. Zheljazkov, Charles L. Cantrell, William B. Evans, M. Wayne Ebelhar, and Christine Coker

There are more than 150 basil species belonging to the genus Ocimum ( Javanmardi et al., 2002 ). The two most widely grown species for essential oil production are holy basil ( Ocimum sanctum L.) and sweet basil ( Ocimum basilicum L.). Basil

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Aditi Satpute, Bryce Meyering, and Ute Albrecht

-temperature conditions following harvest. Sweet basil ( Ocimum basilicum L.), a plant of tropical origin and member of the mint family (Lamiaceae), is grown in many regions around the world. Basil is grown under different climatic and ecological conditions but prefers

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Kelly M. Bowes and Valtcho D. Zheljazkov

Field and laboratory experiments were conducted during the summers of 2001 and 2002 in two locations in Nova Scotia to identify the effect of cultivar, transplanting date, and drying (air-drying and freeze-drying) on basil (Ocimum basilicum `Mesten' and `Italian Broadleaf', and O. sanctum `Local') productivity and oil quality in Nova Scotia and to identify the potential of growing basil as a cash crop in this region. Results suggested that all of the tested cultivars of basil grown in Nova Scotia had acceptable yields and composition for the international commercial market. Greater yields (ranging from 3.6 to 19.8 t·ha-1) were achieved from `Mesten' and `Italian Broadleaf' by earlier transplanting. `Local' had a lower oil content compared to the other cultivars. Linalool was the main component of `Mesten' oil, linalool and methyl chavicol were the main components of `Italian Broadleaf' oil, while elemene and α-humulene were the main components of `Local' oil. Both air-drying and freeze-drying were found to alter the composition of the essential oil from O. sanctum and O. basilicum.

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Renee G. Murray and James E. Simon

Essential oil content of Ocimum basilicum, cv. sweet basil, increases with plant maturity. The increase in essential oil content may correspond to the formation of glandular trichomes during leaf expansion. Greenhouse grown plants were harvested every 2 weeks. Leaves were grouped according to size, examined with a stereo microscope, and trichome densities compared. Results indicate that trichome formation continues throughout leaf expansion. In young basil plants, leaves ranged in size from 2-30cm2 Highest density (416 trichomes/cm2) occurred in leaves 2–6c m2. Prior to open bloom, leaves ranged in size from 2-49cm2. Highest density occurred in leaves 18-24c m2. In flowering plants leaves ranged in size from 2-34cm2, yet there was NSD in trichome density in leaves of different sizes. Analysis of the entire leaf surface of plants at each harvest showed the greatest density of trichomes in plants at full bloom (280 trichomes/c m2). All leaves have visible glandular trichomes. These glandular trichomes are most likely formed both prior to and during leaf expansion.

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Roberto F. Vieira and James E. Simon

To determine the mode of inheritance of citral, linalool, methylchavicol, and methylcinnamate in basil, controlled crosses were made between chemotypes rich in each of these constituents. Four stable Ocimum basilicum populations selected for high methylcinnamate (79%), methylchavicol (95%), linalool (82%), and citral (65%) respectively, served as parents. Crosses were made using chemotypes rich in terpenes (linalool × citral), in phenylpropanoids (methylchavicol × methylcinnamate), and a third that combines chemotypes from both biosynthetic pathways (linalool × methylchavicol). True hybrids were selfed in isolation and one hundred F2 plants were analyzed for their oil composition. The parents, the F1 hybrids and the F2 generation of all plants were evaluated in a field trial under identical environmental conditions. Plants were harvested at full flowering, and dried at 380 °C. Identification of essential oil constituents were confirmed by GC/MS. The F2 segregation data for each major oil constituent trait will be examined by c2 analysis tests. Preliminary results indicate that methylcinnamate segregates in a 3:1 ratio, and is a dominant major gene. In the two crosses using methylcinnamate chemotype as a female parent, the F2 population segregates in 80:22 and 65:28 methylcinnamate:non-methylcinnamate plant types, with P = 0.42 and 0.25 and c2=0.64 and 1.29, respectively. Analysis of the other crosses are being processed, evaluating qualitative and quantitatively the presence or absence of each constituent in their F2 population.

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Liangli Yu, Mario Morales, and James E. Simon

Hydro-distilled essential oils from fresh and dry leaves and fresh and dry flowers of `Sweet Dani', a new ornamental lemon basil (Ocimum basilicum) cultivar with potential as a source of natural citral, were analyzed by GC and GC/MS. The essential oil contents were 0.18%, 0.19%, 0.30%, 0.28% w/w on a fresh weight basis of fresh and dry leaves, and fresh and dry flowers, respectively. Oils from leaves and flowers differed significantly in content and composition. The major constituents in dry leaf oil were neral 21.8% and geranial 33.5%. The major constituents in dry flower oil included: nerol 11.5%, neral 12.9%, geraniol 7.6%, and geranial 17.7%. Nerol (1.6%), and geraniol (0.4%) were very low in dry leaf oil. As citral is a combination of neral and geranial, the relative leaf and flower citral content is 55.3% and 30.6% of the total oil, respectively. Linalool and octanol were detected in flower oils only.

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Diana D. Lange and Arthur C. Cameron

Shelf life (defined by visual quality) of freshly harvested greenhouse-grown sweet basil was maintained for an average of ≈ 12 days at 15C. Chilling injury symptoms were severe at storage temperatures of 5C and below. Shelf life was found to be only 1 and 3 days at 0 and 5C, respectively. Moderate chilling injury was noted at 7.5 and 10C. Harvesting sweet basil later in the day (i.e., 1800 or 2200 hr) increased shelf life by almost 100% when harvested shoots were held at 10, 15, and 20C, compared to harvesting at 0200 or 0600 hr. However, the time of day of harvest did not alter the development of visual chilling injury symptoms or improve shelf life at 0 or 5C.

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Winthrop B. Phippen and James E. Simon

A plant regeneration protocol was successfully developed for basil (O. basilicum L.). Explants from 1-month-old seedlings yielded the highest frequency of regeneration of shoots (37%) with an average number of 3.6 shoots per explant. Calli and shoot induction were initiated on Murashige and Skoog (MS) basal medium supplemented with thidiazuron (TDZ) (4 mg/L) for ≈30 days. Shoot induction and development was achieved by refreshing the induction medium once after 14 days. The most morphogenetically responsive explants were basal leaf explants from the first fully expanded true leafs of greenhouse-grown basil seedlings. Developing shoots were then rooted on MS media in the dark without TDZ. Within 20 days, rooted plantlets were transferred and acclimatized under greenhouse conditions where they developed normal morphological characteristics. This is the first report of a successful in vitro regeneration system for basil through primary callus. The establishment of a reliable regeneration procedure is critical when developing a transformation protocol for enhancing the production of basil for insect and disease resistance and improved essential oil constituents.

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T.J. Radovich, C.G. Cavaletto, and H.R. Valenzuela

The sensory quality of fresh basil (cv. Sweet Italian) was evaluated to determine if compost or mineral fertilizer applications affected flavor and aroma intensity. The four treatments, arranged in a randomized complete-block design with three replications, were: compost applied at 50 t·ha–1; compost applied at 200 t·ha–1; mineral N applied at 110 kg·ha–1; and a control receiving no amendment. Leaves from the first four nodes of young shoots were used in the evaluation. Twelve trained panel members scored samples of three leaves from each treatment for aroma and flavor intensity using a linear scale, converted to a scale of 1–10 where 1 = much less intense than a reference sample (control), and 10 = much more intense than the reference. No significant difference between treatments was found in flavor intensity. Significant difference between treatments in aroma intensity was found. Aroma scores were highest in samples from the compost and synthetic fertilizer treatments, and lowest in those from the control. Scores for aroma from the compost and synthetic fertilizer treatments were similar to each other. Aroma intensity increased with increased rate of compost application. No significant correlation was found between aroma intensity and plant tissue N content, sap NO3 levels, or yield.

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Daniel P. Gillespie, Chieri Kubota, and Sally A. Miller

Rootzone pH affects nutrient availability for plants. Hydroponic leafy greens are grown in nutrient solutions with pH 5.5 to 6.5. Lower pH may inhibit plant growth, whereas pathogenic oomycete growth and reproduction may be mitigated. General understanding of pH effects on nutrient availability suggests likely toxicity and deficiency of specific micronutrients. We hypothesized that if adjustments are made to the micronutrient concentrations in solution, plants will grow in lower-than-conventional pH without nutrient disorders, while oomycete disease incidence and severity may be reduced. To develop a new nutrient solution management strategy, we examined pH of 4.0, 4.5, 5.0, and 5.5 with or without micronutrient adjustments for growing two cultivars of basil plants Dolce Fresca and Nufar in a greenhouse hydroponic deep-water culture (DWC) system. Micronutrient adjustments included reduced concentrations of copper, zinc, manganese, and boron by one-half and doubled molybdenum concentration. Plants harvested 20 to 28 days after transplanting did not show significant effects of pH or the micronutrient adjustment. Phosphorus, calcium, magnesium, sulfur, boron, manganese, and zinc concentrations in leaves significantly declined, while potassium and aluminum concentrations increased with decreasing pH. However, these changes and therefore micronutrient adjustments did not affect basil plant growth significantly. ‘Nufar’ basil plants were then grown in a growth chamber DWC system at pH 4.0 or a conventional 5.5 with and without inoculation of Pythium aphanidermatum zoospores. Fourteen days after inoculation, P. aphanidermatum oospore production was confirmed only for the inoculated plants in pH 5.5 solution, where a significant reduction of plant growth was observed. The results of the present study indicate that maintaining nutrient solution pH at 4.0 can effectively suppress the severity of root rot caused by P. aphanidermatum initiated by zoospore inoculation without influencing basil growth.