Genetic diversity and inheritance of volatile oil constituents in basil (Ocimum spp. - Lamiaceae)
Abstract
Essential oils extracted from basil (Ocimum spp.) are used to flavor foods, oral products, in fragrances, and in traditional medicines. The genus Ocimum contains around 30 species native to the tropics and subtropics, with species cultivated in temperate regions. Taxonomy of basil Ocimum is complicated by inter- and intra-specific hybridization, and the existence of numerous cultivars and chemotypes within species that do not differ significantly in morphology. We hypothesized that volatile oils, flavonoids and molecular markers could provide complementary tools to better understand the species taxonomy. Results indicated that multivariate analysis of aromatic volatile oils and flavonoids using principal component analysis were able to separate basil accessions. RAPD markers were used to characterize the genetic diversity among nine Ocimum species (O. americanum, O. basilicum, O. campechianum, O. xcitriodorum, O. gratissimum, O. kilimandscharium, O. minimum, O. selloi, and O. tenuiflorum), a total of 37 accessions. Using RAPDs, we were able to detect significant genetic diversity based on 98 polymorphic fragments generated, and were able to discriminate between all Ocimum species. There was a high degree of similarity within O. basilicum. A significant correlation between flavonoids, volatile oils and RAPD was achieved only for the twelve O. gratissimum accessions. Inheritance of natural plant products and aromatic volatile oil compounds is poorly understood. To test the hypothesis that methylcinnamate and methylchavicol in basil are inherited as single independent genes, a first step toward the use of bulk segregant analysis to select molecular markers, controlled crosses were made between chemotypes-rich in each of these constituents. Stable Ocimum basilicum populations selected for high methylcinnamate (79%), methylchavicol (95%), and linalool (82%) respectively, served as parents. Crosses were made using all these chemotypes: (methylchavicol x methylcinnamate; linalool x methylchavicol; linalool x methylcinnamate). True hybrids were selfed in isolation and F2 Plants were analyzed for their aromatic volatiles. The parents, F1 hybrids and the F2 generation were evaluated under both greenhouse and field conditions. Identification of essential oil compounds were confirmed by GC/MS. The F 2 segregation data was analyzed by chi-square test. Results show a single and independent inheritance of both methylcinnamate and methylchavicol.
Degree
Ph.D.
Advisors
Simon, Purdue University.
Subject Area
Genetics|Botany|Molecular biology|Plant sciences
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