Antibiotics are substances which are produced by micro- organisms and which act against micro-organisms. Most antibiotics known uptill now are products of actinomycetes and some are from fungi and bacteria. Some of the important antibiotics are mentioned here.
1. Streptomycin: Streptomycin is produced by the actinomycete Streptomyces griseus. Streptomycin is also sold as agrimycin, phytomycin, ortho-streptomycin etc. It is sprayed to control Xanthomonas citri (citrus canker), bacterial leaf spot of tomato and pepper, hollow blight of french bean and fire blight of apples and pears. It is also used as a dip for potato seeds against various bacterial rots of tubers and as a seed disinfectant in bacterial pathogens of beans, cotton, crucifers, cereals, etc.
2. Cycloheximide: Cycloheximide is also known as actidion, actispray, Iactidione PM, actidione RZ etc. It controls mildew of beans, covered smut of oats, brown rot of peach, Tilletia spp etc. It is it active against a wide range of fungi and yeasts but is inactive against bacteria.
3. Griseofulvin: Griseofulvin is produced by Penicillium griseofulvwn, P. patulum, P.digricans and P. jancyewski. It is effective against downy mildew of cucurbits, powdery mildew of rose, powdery mildew of beans, early blight of tomato and brown rot of apple. The dosage of foliar spray varies from 100-1000 ppm.
4. Blasticidins: It is produced by Streptomyces griseochromogenes. It is active against both bacteria and fungi but is selective in its activity.
5. Aureofungin: It is produced in the submerged cultures of Streptomyces cinnamomens. The most useful property of the antibiotic is its high activity against a large number of phytopathogens and; its absorption and translation in living plants. Downy mildew, powdery mildew and anthrancnose of grapes are controlled by spraying. Seed treatment of rice controls Helminthosprium oryzae. Pyricularia oryzae of rice. Diplodia of mango, Alternaria rot of tomato, Sclerotinia rot of peach, Pythium rot of cucurbits etc are controlled by this antibiotic.
6. Tetra cyclones: Tetra cyclines are produced by a number of species of streptomyces. It is effective against crown gall, fire blight of apples etc. Recently it has been found that it is effective against mycoplasmas also.
7. Agrimycin-l00: Agrimycin-100 is 15% streptomycin sulphate and 1-5% terramycin. Agrimycin -500 is 1.75% streptomycin sulphate, 0.176% terramycin and 42.4% metallic copper. It is effective against halo blight, citrus. canker, seedling blight, leaf spot, and black arm disease of cotton and soft rot and black leg of potato.
8. Antimycin: Antimycin is produced by several species of streptomyces including S. Kitasawensis and S.griseus. It is effective against early blight of tomato, seedling blight of oat, rice blast etc.
9. Thiolutin:Thiolutin is water soluble antibiotic produced by Streptomyces albus. It controls late blight of potato and downy mildew of broccoli in limited scale.
10. Mystatin: Mystatin is also known as mycostatin or fungicidin. It is an antifungus antibiotic produced by streptomyces noursei. It controls anthracnose of beans and downy mildew of cucumber. Also used as seed treatment against stripe disease of barley.
11. Bulbifonnin: Bulbiforrmin.is an antifungal antibiotic produced by Bacilus subtiles. It controls wilt of pigeon pea.