Changes in ploidy and its effect on thymoquinone concentrations in Nigella sativa L. seeds

Abstract

SUMMARYColchicine-induced changes in ploidy levels provide an opportunity to improve the morphological and biochemical attributes of plants. Concentrations of metabolites have been shown to be affected by changing the ploidy level of the genome. Nigella sativa L. has long been used as a traditional spice and a medicinal herb, and recent scientific reports have increased its pharmaceutical and industrial applications. Ploidy effects were investigated following the application of 0.025, 0.05, or 0.10% (w/v) colchicine, and several changed levels of ploidy (aneuploidy, triploidy, or tetraploidy) were scored. The aneuploid seedling had one telocentric chromosome missing and did not survive beyond the juvenile stage. Triploids and tetraploids exhibited large-scale morphological characteristics such as thicker and darker-green leaves, and increased numbers of branches compared to diploid plants. Increased ploidy improved the morphogenetic behaviour of the tetraploid plants, but these plants exhibited stalk-lodging at maturity. Most of the triploid plants recovered by losing the extra chromosomes from their genome in succeeding generations, with the effect that seed-set returned to normal, as in the diploids. Other triploid plants did not set C2 seed. Tetraploid plants also revealed low levels of segregation in the C2 and later generations. Careful selection and screening, based on morphological and biochemical characteristics, established 32 tetraploid lines of N. sativa with approx. 46% higher concentrations of thymoquinone in the oil of their seed.