Genetic Analysis of Some Chemotypes in Ocimum basilicum var. glabratum

Screening of a population of Ocimum basilicum var. glabratum Benth., raised from seeds collected from France, West Africa and Kerala (India) was carried out for chemical composition of its essential oils. In all three collections, plants were found to be comprised of 3 chemotypes which were morphologically indistinguishable, but each chemotype was found to be capable of intercrossing freely with the other two. Selfing was carried out during 4 consecutive generations, after which three pure lines were established. Study of the selfed progeny of each collection exhibited an interesting segregation in S₂ and S₃ generations. Along with segregation in F₂ and F₃ generations of various hybrids the results can be explained by assuming a gene ‘M’ existing in 3 (or more) allelic forms: The allele M₀ for biosynthesis of estragole (methyl chavicol) is dominant to allelcs M₁ , for eugenol and M₂ for camphor. Also, allele M₁ is dominant to allele M₂ . The assumption was further confirmed by testcrosses of F₁ hybrids of each cross with their recessive parent.