Seed yield, yield components, oil content and essential oil content and composition of Nigella sativa L. and Nigella damascena L

Nigella sativa and Nigella damascena are two annual species of the family Ranunculaceae, investigated recently for the oil, essential oil and other biologically active constituents of their seeds. They are presently used in traditional medicine and for culinary preparations in many countries, as ornamentals, and are also considered for their abundant nectar secretion. One accession of N. sativa and two of N. damascena were compared on three spring sowing dates in northern Italy. Seed yield, yield components, essential oil content and composition were evaluated. Oil content was also measured in N. sativa. Total and seed biomass decreased with delayed sowing, because of a reduction in both seed number per plant and mean seed weight. Seed number per plant was the more important yield component for both species. Actual seed yield was lower for N. sativa, whereas yield potential seemed to be similar for the two species. The main constraint to yield potential of N. sativa seemed to be connected to its short vegetative phase, with consequently low number of seeds per unit area. The essential oil composition differed markedly in the two species. Monoterpenes were dominant in N. sativa, with p-cymene and thymol as the main components. The amount of pharmacologically active thymoquinone was lower than reported in the literature. N. damascena essential oil was almost completely composed of sesquiterpenes. Essential oil composition was very stable in N. damascena, but markedly affected by sowing date in N. sativa. Oil yield of N. sativa decreased with delayed sowing. As a whole, the two species had positive agronomic traits, such as short growing cycle, low seed shattering and low susceptibility to diseases. This, together with different possible options for direct utilisation or industrial processing, may determine an interest in further considering the two species as potential new multi-purpose crops.