Generation and characterisation of colchicine-induced polyploid Lavandula × intermedia

Lavandula × intermedia (lavandins) are naturally occurring hybrids of Lavandula angustifolia (lavender) and Lavandula latifolia (spike lavender) which are grown for their essential oil and as garden ornamentals. Lavandins are higher yielding plants than lavenders but produce camphoraceous, inferior quality oils. They are invariably infertile. The majority of oil produced worldwide from the genus comes from lavandins. To produce larger higher yielding lavandins we induced polyploidy in the common cultivars Grosso and Seal with the mitotic spindle inhibitor colchicine, using whole plants, cutting material and tissue culture. Polyploid plants were identified by restoration of fertility and the production of seed, regardless of the plant tissue used. These fertile lavandins were morphologically similar to the parents. Using flow cytometry (FCM) we determined one of these plants to be mixoploid having distinct diploid and tetraploid nuclei. Seed from this plant was twice the weight of L. angustifolia seed. Ten plants were grown from seed collected from the colchicine treated lavandins Grosso and Seal. All had similar overall morphology to the parents but were larger plants with larger flowers. One plant derived from Seal and one from Grosso were found to be triploid by FCM and all 20 plants were found to be infertile. The C-values of the three species within section Lavandula, the lavandins Grosso and Seal and the polyploids resulting from this work were determined by FCM. The novel fertile lavandin characterised may be useful for extending the range of hybrids possible within the genus for both production of essential oils and ornamentals.