Shaima T.B., Sowmya and Kunhi A.A.M. 2016. Inhibitory Effect of o-Cresol on Germination of Eggplant Seeds and its Elimination through Bioremediation of o-Cresol-Spiked Soil by Pseudomonas monteilii S-CSR-0014. Abstract Book. National symposium on ‘Biosciences and Technology –Recent Developments and Future Prospects’, SIAS-Centre for Scientific Research, Safi Institute of Advanced Study, Vazhayoor, Malappuram, Kerala, pp. 30-31.

ABSTRACT

Cresols are chemical compounds ubiquitous in nature due to their generation in various industrial processes such as petroleum refining, coal gasification, dye manufacturing, and petrochemicals, pharmaceutical and resin manufacturing as well as due to their natural presence. o-Cresol (2-methyl phenol), one of the isomers is highly toxic to both fauna and flora and has been included as one of the priority pollutants in the EPA list. There are several reports on the deleterious effects of pesticides, herbicides, and many other chemical compounds on seed germination. However, there is no report on the effect of o-cresol on seed germination and hence, this study was taken up. The effects of different concentrations of o-cresol on germination of seeds of 10 different vegetable crops were tested by the standard Filter Paper Method (FPM). o-Cresol had no apparent adverse effect on the germination of tomato, pumpkin, okra, red chilli, spinach and cucumber seeds up to a concentration of 1200 mg/l. However, long-podded cowpea (Vigna unguiculata subsp. sesquipedalis) and eggplant (Solanum melongena) were found to be highly sensitive to o-cresol. S. melongena being the most sensitive in filter paper method it was tested further by Soil Method which also exhibited high sensitivity to o-cresol. Germination percentage and seedling vigour (Vigour Index) were drastically reduced in the presence of the chemical. The percent germination was reduced to 64 and 32 at 100 and 200 mg o-cresol/kg soil as against 100% in the case of untreated control. The Vigour Index was reduced to 156.6 and 68.16, respectively as against 817 that for the control. A number of abnormalities were also observed in the seedlings. The viability of seeds by TTC test showed marked reduction proportional to the concentration of o-cresol which reached almost zero level at 175 mg/l of the chemical, indicating the interference of o-cresol in the respiratory activity of seeds. Changes in the activities of protease and amylase enzymes, which are the key enzymes involved in the mobilization of stored nutrients during germination were also observed. Protease activity exhibited a decrease up to day 3 and then an increase until day 6 which declined then onwards in the case of control seeds whereas seeds exposed to 150 mg o-cresol/kg soil continued to decrease untilday 7. Protease in seeds exposed to 50 mg/kg showed a decline until day 5 and then slightly increased. In contrast to previous reports amylase enzyme showed higher activities in treated seeds both treated and untreated seeds showed the same pattern. The inhibition caused by exposure to o-cresol was revoked by inoculation of the soil with Pseudomonas monteilii S-CSR-0014, a cresol-degrading laboratory isolate, enabling normal germination of the seeds. The inoculated bacterial strain exhibited good survival and growth in o-cresol-spiked soil efficiently utilizing the chemical. It can be concluded that by bacterial bioremediation of o-cresol-contaminated soils the inhibition of higher activities in treated seeds both treated and untreated seeds showed a decline in activity until day 5 and then an upward trend. The inhibition caused by exposure to o-cresol was revoked by inoculation of the soil with Pseudomonas monteilii S-CSR-0014, a cresol-degrading laboratory isolate, enabling normal germination of the seeds. The inoculated bacterial strain exhibited good survival and growth in o-cresol-spiked soil efficiently utilizing the chemical. It can be concluded that by bacterial bioremediation of o-cresol-contaminated soils the inhibition of germination of sensitive crop seeds could be eliminated and crops could be raised effectively.

Keywords:Bioremediation, Pseudomonas monteiliis, Seed germination.