EFFECTS OF SEED IRRADIATION ON YIELD AND QUALITY OF ESSENTIAL OIL IN PALMAROSA (CYMBOPOGON-MARTINII STAPF)

Dry seeds of palmarosa (Cymbopogon martinii STAPF) var. motia were subjected to 12 doses of gamma rays ranging from 5 kr to 100 kr to find out the effects of gamma irradiation on growth parameters, herbage yield and yield and quality of essential oil. Several biological parameters such as seedling growth, pollen fertility, mitotic chromosome behaviour, productive tillers/plant, leaf area index, leaf/stem ratio (by fresh weight) and total herbage yield/plant together with yield and quality of oil have been studied in the first (M1) generation. Marked stimulatory effects of gamma radiation in 10 kr and 15 kr doses have been compared with the control for herbage yield, oil percentage and total alcohols (free geranyl and geranyl acetate). The two yield contributing traits, herbage yield/plant and leaf area index were remarkably increased in 15 kr, which indicates that in palmarosa the 15 kr dose is more effective than the higher doses in producing microlevel mutations. The yield and quality of oil at 10 kr and 15 kr doses were enhanced significantly. The results on high yield and quality of oil as induced by gamma-irradation were discussed from the point of view that a gene may have been altered by mutagen treatment to produce a metabolic block between geraniol and geranyl acetate on the biosynthetic pathway or that ''modifier'' genes controlling the expression of a key precursor molecule may have been further modified to give rise to a geraniol rich ''chemotype'' in palmarosa.