Genetic improvement of palmarosa (Cymbopogon martinii var. motia) for herbage and essential oil yield through polycross method of breeding

Palmarosa (Cymbopogon martinii var. motia) is an important essential oil-bearing plant that is used worldwide in the soap, perfumery and cosmetic industries. It is a highly cross-pollinated crop and can be propagated sexually through seeds or clonally by slips. The main objective of the present investigation is to collect populations of palmarosa from different parts of India, to analyse the variability present within and between population, to study the correlation of different traits and to select the best performing clones in terms of growth, herbage and essential oil yield for raising the best performing clones in polycross nursery. The seeds of seven populations/varieties were collected from various parts of India and two hundred seedlings of each population were raised and transplanted to the field at the ICAR-Directorate of Medicinal and Aromatic Plants Research, Anand, Gujarat, India. Observations on individual plants performance viz., plant height, number of tillers, dry herbage yield and essential oil yield were analysed for five harvests which were taken over a period of two years. For plant height, a maximum frequency of 32 per cent was recorded from 141 to 150 cm in PRC-1, whereas, for the number of tillers it was 31.88 per cent from the Bengaluru collection that was between 81 and 110 tillers. Fresh and dry herbage yield showed a significant positive correlation with plant height, the number of tillers and oil yield. The correlation between dry herbage yield and the number of tillers was maximum (0.761), followed by dry herbage yield and essential oil yield (0.563) and the number of tillers and oil yield (0.417). Interestingly, a significant correlation of oil yield with plant height and number of tillers gives an indication that the improvement of the traits will not only increase the dry herbage yield but also increase the essential oil yield. Based on the performance of individual clones out of 642 clones evaluated, the best fifteen clones were selected based on the dry herbage and essential oil yield and named as DCM-1 to DCM-15. These clones were further utilized for raising polycross nursery.