**4. Discussion**

Natural products isolated from higher plants have been providing novel, antimicrobial drugs. Historically, many plant oils and extracts, such as tea tree, clove, Etc. have been used

An Alternative Approaches for the Control of

antimicrobial resistance.

43, *2*, 149-153.

*Microbiology*, 37(5):1480-1483.

*producing plants*, pp 122-125.

Horne, C. W., and R. A. Frederiksen, 1993.

305-311.

32:11-4.

review., 1-22.

Group.

484-495.

111.

**5. References** 

Sorghum Pathogens Using Selected Medicinal Plants Extracts 143

In view of the changing agricultural policies throughout the world complete disease control is no longer a target of plant pathologist's reducing the threshold level using cost-effective and eco-friendly management option is the focus of the day. In this context identification of aqueous leaf extract of *T. chebula* and *M. azadirach* methanol extracts as bactericides and fungicides against the pathogens tested are highly significant recommendable. The result of these studies maybe helpful in developing/synthesizing the plant based natural fungicides and insecticides that may be for preventing and curing the common destructive diseases of *Sorghum* crop and other cereal crops. In this context the studied plant extracts is more appropriate and helpful in synthesizing the plant based biofungicides to reduce the pathogen population to lower economic threshold level using cost effective and eco friendly management. This will also offer a great help in facing the emergence spread of

Akhtar M.A., M.H. Rahber-Bhatti, M. Aslam, *International Journal of Pest Management*, 1997,

Cardellina J. H. (1988): Biologically active Natural Products: Potential Use in Agriculture,

Darout, I., Cristy, A., Skaug, N., and P. Egeberg, 2000. Identification and quantification of

Elizabeth, M., Adrien Szekely, Johnson and David W. Warnock., 2001. *Journal of Clinical* 

Fundter, J.M., *et al.,* 1992. *Terminalia chebula* Retz. In Lemmens, R.H.M.J. & Wulijarni-

Grierson DS, Afolayan AJ (1999). An ethnobotanical study of plants used for the treatment of wounds in the Eastern Cape, South Africa. Ethnopharmacol 67: 327-332. Gulter H.G. (1988): Natural products and their potential in agriculture. A personal over

Hoffman, D. L. 1987. *The Herb User's Guide*. Wellingborough, UK: Thorsons Publishing

Jacobson, M., 1995. In the Neem Tree: Source of Unique Natural Products for Integrated Pest

Janovska, D., Kubikova, K., Kokoska, L. 2003. Screening for antimicrobial activity of some

Jaspal Singh., and N. N. Tripathi., 1993. *Journal of the Indian Botanical Society*, 72 (1-2) :51-53. Kaushik, R. D. and Charu Arora, 2002. Fungitoxic activity of methanol extracts of some

*Journal of Indian botanical sciences*, 81:327-331.

Management, Medicine, Industry and other Purposes (ed. Schmutterer, H.), pp.

medicinal plant species of traditional Chinese medicine. *Czech. J. Food Sci*. 21: 107-

plants of kamaun, garhwal and tarai regions against fungal pathogens of rice.

(http://www.apsnet.org/online/common/names/sorghum.asp).

some potentially antimicrobial anionic components in Miswak extract. *Ind J Pharm*,

Soetjipto, N. (Eds.): Plant Resources of South-East Asia. No. 3: *Dye and tannin-*

as topical antiseptics, or have been reported to have antimicrobial properties (Hoffman 1987 and Lawless 1995). It is important to investigate scientifically those plants which have been used in traditional medicines as potential sources of novel antimicrobial compounds (Mitscher *et al.,* 1987). Also, the resurgence of interest in natural therapies and increasing consumer demand for effective, safe, natural products means that quantitative data on plant oils and extracts are required.

Majority of studies conducted the search of compounds with antimicrobial properties have targeted plants with a history of ethno botanical uses (Janovska *et al.,* 2003), most of the medicinal plant species screened in this study were previously been surveyed for antimicrobial activities on human pathogens. And very few citations were reported on phytopathogens (Kaushik and Arora, 2003; Jaspal singh and Tripathi, 1993; Krishna kishore and Suresh pande, 2005; Meena and Goplakrishnan, 2005). The observed antimicrobial activity of these plant extracts, and isolated compounds were of highly remarkable.

The present study was designed to obtain information on the antimicrobial effect of 50 Indian medicinal plants on certain plant pathogenic microorganisms. The well diffusion/cup plate method was used in this study since it was found to be better than the disc diffusion method. All the medicinal plant extracts and isolated compounds showed antimicrobial activity against selected pathogens of Sorghum.

Hexane extracts never showed antimicrobial activity. The chloroform and water extracts showed very less antimicrobial activity compared with methanol extracts. This may be due to little diffusion properties of these extracts in the agar or because fresh plants contain active substances which may be affected or disappeared by the steps of extraction methods.

The methanol extracts of all the medicinal plant screened (Table-1) exhibited grater antimicrobial activity. According to Darout *et al.,*(2000) the antimicrobial action of methanol extracts is due to the compounds such as thiocynate, nitrate, chloride and sulphates beside other high polarity soluble compounds which are naturally occurring in most plant materials.

Methanolic extracts of *T. chebula, B. Montana, M. azadirach, W. somnifera, O santum* and *P. pterocarpum* showed greater antimicrobial activity. *Terminalia chebula* possessed 32-40% of tannin content and the antibacterial activity may be indicative of the presence of some metabolic toxins or broad-spectrum antibiotic compounds (Fundter *et al.,* 1992). *M. azadirach* was exhibited good antimicrobial activity against most of the tested pathogens in this study. According to Jacobson, (1995) this activity is due to Nimbidin, extracted from *M. azadirach* demonstrated several biological activities. From this crude principle some tetranortriterpenes, including nimbin, nimbinin, nimbidinin, nimbolide and nimbidic acid have also been showing antimicrobial activities.

The observations reveal that tested medicinal plant methanol extracts activity against all phytopathogenic species. As evidenced, the fungal strains that were sensitive are *M. phaseolina*, *R. solani* species, *C. graminicola* and *F. moniliforme* found to be resistant strains. Among the tested medicinal plants methanol extracts against the phytopathogenic species, *Terminalia chebula* extracts showed greater antimicrobial activity on all plant pathogens.

In view of the changing agricultural policies throughout the world complete disease control is no longer a target of plant pathologist's reducing the threshold level using cost-effective and eco-friendly management option is the focus of the day. In this context identification of aqueous leaf extract of *T. chebula* and *M. azadirach* methanol extracts as bactericides and fungicides against the pathogens tested are highly significant recommendable. The result of these studies maybe helpful in developing/synthesizing the plant based natural fungicides and insecticides that may be for preventing and curing the common destructive diseases of *Sorghum* crop and other cereal crops. In this context the studied plant extracts is more appropriate and helpful in synthesizing the plant based biofungicides to reduce the pathogen population to lower economic threshold level using cost effective and eco friendly management. This will also offer a great help in facing the emergence spread of antimicrobial resistance.
