Determination of essential oil quality index by using energy summation indices in an elite strain ofCymbopogon citratus (DC) Stapf [RRL(J)CCA12]

Out of the several accessions of Cymbopogon citratus (DC) Stapf introduced from Central and West India, one accession coded as RRL(J)CCA12, selected through a mass selection technique, was found to have citral (≈80%) as the major constituent in its essential oil. Citral has tremendous application in the flavour and perfume industries. Plant adaptation was judged by quantifying the regression coefficient (b) value, which was 1.0 using essential oil growth indices. For prediction of essential oil quality index (EOQI), a multiple regression equation was developed for the first time by using essential oil yield/plant and energy summation indices as EOQI (citral %) = 61.6 + 1.09 × essential oil yield/plant (g) - 0.005 × heat use efficiency + 0.675 × phenothermal index. For obtaining a better quality of essential oil (citral ≥78%), the optimal value of independent variable would be: X1 = 2.49; X2 = 0.018 and X3 = 20.47, where X1, X2 and X3 denote essential oil yield/plant, heat use efficiency and phenothermal index, respectively. The validation of the EOQI model is done by correlating the predicted and calculated values of citral (%) which exhibited significant r value = 0.955 at 5% probability level. The thermal requirement of the selectant was ≈5500 degree days to exhibit plant maturity in terms of qualitative and quantitative characteristics of its essential oil at 6.0 vegetative leafing stage, with attainment of plant height ≥1.0 m from previous date of harvest (December 2001). Prediction of essential oil quality by using the mathematical model is helpful for integrating the growth processes and evaluating crop management strategies. Copyright © 2004 John Wiley & Sons, Ltd.