Genetic and cytogenetic structure of wild lemon grass (Elionurus muticus ) populations

Elionurus muticus is a native aromatic grass from the Pampa biome that produces an essential oil that is rich in citral. Despite the importance of citral, few studies have examined this species. The aims of this work were to evaluate the genetic structure and to characterize cytogenetically natural populations collected from Brazil. Genetic characterization was performed using AFLP markers, and cytogenetics assessed the chromosome number, karyotype and meiosis. The studied populations had genetic variability, especially within populations, indicating the possibility of selecting plants with relevant characters. High variability also suggests the preferential occurrence of outcrossing in natural populations. Regular meiosis was observed in the cytogenetic analysis with chromosome number 2n=20. The karyotype of the species is presented for the first time, with the karyotype formula 3sm + 4a + 1saSAT.

Effects of applications of N fertilizers and nitrification inhibitors on dry matter and essential oil yields of Java citronella (Cymbopogon winterianus Jowitt.)

A field experiment was conducted for 2 years (1993–95) at Central Institute of Medicinal and Aromatic Plants, Field Station, Bangalore, India to evaluate the nitrification inhibitors, benzotriazole, o-nitrophenol, m-nitroaniline and dicyandiamide in a perennial aromatic grass, Java citronella. Citronella responded to applications of high doses of nitrogen (300 kg N/ha/year). The interaction between N doses and nitrification inhibitors was significant. Nitrification inhibitors performed better at the highest N dose (450 kg N/ha/year) and the increase in the essential oil yields was to an extent of 27·3 to 34·6% when compared with ‘N alone’ treatment. The nitrification inhibitors also increased the apparent N recoveries by citronella considerably. The oil content in the herb and its quality were not affected by the treatments. The nitrification inhibitors increased citronella yields and improved N economy.

Productivity and economic viability of a palmarosa–pigeonpea intercropping system in the subtropical climate of north India

The poor viability of the perennial aromatic grass, palmarosa (Cymbopogon martinii Stapf. var. motia), in the first year of planting, restricts its popularity among farmers in India. Two pigeonpea cultivars, Bahar (late maturing), and UPAS–120 (early maturing) were intercropped at different row spacings with palmarosa at a row spacing of 60 cm, in the subtropical climate of Lucknow, north India in 1988/89 and 1989/90. Intercropping with the late maturing cv. Bahar at 300 cm row spacing produced 1·26 t/ha grain (2-year mean) without affecting the growth and yield of the palmarosa. Intercropping improved land-use efficiency by 47%, relative net return by 58% and net economic return by Rs. 12500/ha over a sole palmarosa crop. The grain, stalk and total dry matter yield per plant of pigeonpea was considerably improved when grown at the wider row spacing in the intercropped system than when grown as a sole crop. This indicates that the competition between pigeonpea plants was not reduced when palmarosa was present. Palmarosa tiller production and herb and oil yield were significantly reduced when the distance between rows of pigeonpea was narrowed, demonstrating both the greater susceptibility of palmarosa to lack of light, and also that in palmarosa–pigeonpea intercropping systems, competition exists mainly for light rather than for nutrients and moisture, possibly because the two crop components acquire their nutrients and moisture from different soil layers.Intercropping with the high yielding, late maturing pigeonpea cultivar, Bahar, at 300 cm row distance is recommended to make palmarosa cultivation economically viable in the first year of planting. The selection of high yielding, late maturing pigeonpea cultivars with an upright growth habit is suggested as a further way of improving the economic benefits of a palmarosa–pigeonpea intercropping system.