Mario R. Morales and James E. Simon
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.
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.
Roberto F. Vieira, Peter Goldsbrough, and James E. Simon
Molecular markers were used to assess genetic diversity in basil (Ocimum L. spp., Lamiaceae). Using randomly amplified polymorphic DNA (RAPD) analysis, 11 primers generated 98 polymorphic bands, ranging from 300 to 2,000 base pairs, that discriminated among 37 accessions across nine Ocimum spp. Means of genetic similarities within Ocimum spp. showed that the domesticated species, O. minimum L. (0.887), O. basilicum L. (0.769), and O. ×citriodorum Vis. (0.711) had highest similarity indices within species, while the nondomesticated, O. americanum L. (0.580), O. gratissimum L. (0.408), and O. kilimandscharicum Guerke (0.559) showed the lowest similarity. RAPD results indicated that O. minimum should not be considered a distinct species but rather a variety of O. basilicum. Consistent clusters among all but one of the O. ×citriodorum spp., all containing citral as the major constituent, were identified using bootstrap analysis. RAPD analysis was useful in discriminating among Ocimum spp., although within species resolution will require a higher number of polymorphic bands.
Yan Wang and Stanley J. Kays
The sweetpotato weevil (SPW) [Cylas formicarius elegantulus (Summers) (Coleoptera: Curculionidae)] is the single most devastating pest of the sweetpotato [Ipomoea batatas (L.) Lam.] worldwide. Attempts to develop host-plant resistance have been only moderately successful due in part to deficiencies in parent and progeny selection methods. Host-plant phytochemicals play critical roles in insect behavior, modulating a cross-section of key behavioral decisions. Thus, identification of the phytochemicals the female weevil uses in decision making could greatly facilitate development of host-plant resistance. The volatile chemistry of the sweetpotato was studied in relation to the host-finding behavior of the female weevil. Critical biologically active volatiles were determined via isolation (Tenax trapping), fractionation (gas chromatography-thermal conductivity detector), identification (gas chromatography and gas chromatography-mass spectroscopy), and bioassay (olfactometry). Differences in volatile chemistry among sweetpotato clones that may relate to differences in resistance or susceptibility to the female SPW were assessed. Volatile extracts from storage roots (site of oviposition) and aerial plant parts were attractive to female SPW, the former being substantially greater. In total, 33 compounds were identified from storage roots and aerial plant parts, including 23 terpenes. Three oxygenated monoterpenes (nerol, Z-citral, and methyl geranate), found in storage roots but not aerial plant parts, were identified as attractants. The sesquiterpene volatile fraction was repellent to female SPW with α-gurjunene, α-humulene, and ylangene active in the concentration range emanating from storage roots. The aerial plant parts emanated a higher composite concentration of sesquiterpenes than storage roots. Differences in the relative attraction among four sweetpotato cultivars to female SPW was inversely correlated with the composite concentration of headspace sesquiterpenes. Selection of clones with decreased volatile attractants and/or increased deterrents using an analytical means of quantification may significantly facilitate developing resistance to the SPW.
Christian A. Wyenandt, James E. Simon, Margaret T. McGrath, and Daniel L. Ward
, secondary plant products that are constituents of the plants' aromatic volatile oils, also known as essential oils. It is the presence and relative ratio of these major and minor volatile constituents such as linalool, methyl chavicol, citral, eugenol
Orapin Kerdchoechuen, Natta Laohakunjit, Sasathorn Singkornard, and Frank B. Matta
include β-caryophyllene in hairy basil or O. tenuiflorum L. ( Simon et al., 1990 ) and citral in O. citriodorium Vis. ( Grayer et al., 1996 ; Morales et al., 1993 ; Simon et al., 1990 ). The toxicity of essential oils often varies as a result of
Elizabeth A. Baldwin, John W. Scott, and Jinhe Bai
the years and seasons ( Table 6 ) including acetaldehyde, hexanal, trans -2-pentenal, cis -3-hexanal, trans -2-hexenal, 2 + 3-methylbutanal, trans -2-heptenal, phenylacetaldehyde, methional, benzaldehyde, citral, trans -2, trans -4-decadienal
Jinhe Bai, Elizabeth Baldwin, Jack Hearn, Randy Driggers, and Ed Stover
standards for both harvests ( Elston et al., 2005 ). Other important terpene compounds included two terpene alcohols, linalool, and α-terpineol and two terpene aldehydes, citral and sinensal ( Tables 1 and 2 ). Both linalool and α-terpineol were detected
Chaowei Song, Qi Wang, Jaime A. Teixeira da Silva, and Xiaonan Yu
system, optically active substances such as D-limonene, ( E )-3,5-dimethyl-1,6-octadiene, ( R )-citronellol, ( Z )-nerolidol, ( E )-(+)-nerolidol, ( Z )-3-hexenyl acetate, ( Z )-3-hexen-1-ol, ( E )-2-hexen-1-ol, ( E )-citral, ( E )-rose oxide, and others