In the study, essential oil extraction from turmeric was carried out using modified microwave distillation system and rotary evaporator unit. In present study, effect of input parameters i.e. microwave power (200, 250, 300, 350 and 400 W) and extraction time (10, 15, 20, 25 and 30 min.) on physical properties (oil yield, specific gravity, refractive index and colour) of essential oil were studied. Fixed ratio samples (1:1:1) i.e. turmeric powder, solvent and distilled water was used during the experiment conducted. Essential oil yield using hexane varied from 1.895% to 4.973% while from 0.180% to 1.226% using petroleum ether solvents. Quality parameters varied i.e. specific gravity from 0.910 to 0.923, refractive index from1.478 to 1.506, colour values for oil ranges L* from 70.60 to 98.60, a* from –25.60 to 15.1 and b* from 82.1 to 88.5. Optimum values of process parameters for maximum oil recovery (4.973%) and best quality of oil (specific gravity: 0.915; refractive index: 1.485) was found at microwave power 300 W and extraction time 20 min.

SummaryThe interaction between Phytophthora infestans and potato viruses X (PVX) and Y (PVY) was studied in the potato cultivar Kufri Chandramukhi. Prior infection by PVX and PVY reduced the susceptibility of the plants to P. infestans. The reduction in susceptibility was more marked when leaflets were inoculated with P. infestans 72 h after inoculation with PVY. The same type of reaction was observed in whole plants when the interval between PVY and P. infestans inoculation was 30 days. No significant differences were observed when the sequence of inoculation was reversed.

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S U M M A R YFactors influencing potato virus X (PVX)-induced resistance to Alternaria solani in potato leaves are reported. The inhibition of fungal infection was dependent on the time interval between viral and fungal inoculations, fungal inoculum load, age of the host, virus strain and host cultivar. The maximum reduction in fungal infection was observed when a gap of 120 h occurred between PVX and A. solani inoculations. The clearest interactive effect in terms of reduced susceptibility to A. solani infection was seen at a fungal spore concentration of 1000 spores/ml in 20-day-old plants. This effect was gradually reduced following an increase in inoculum load and age of the host.The extent of pathogen interaction was also affected by different virus strains and host cultivars. Maximum inhibition of fungal disease occurred with the PVX-ring spot strain. Of five potato cultivar tested, the maximum inhibition occurred in Kufri Chandramukhi and Kufri Sindhuri, the cultivars most susceptible to A. solani.

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