Biofumigation-a Sustainable Alternative to Chemical Control of Soil Borne Pathogens: A Review

The phytopathogenic bacterial and fungal microorganism species are among the most common soil-borne pathogens of plants. Soil-borne plant pathogenic fungi cause a plethora of diseases, such as root rot, stem rot, crown rot, damping-off vascular wilts etc., resulting in significant economic losses in the yield and quality of agricultural and horticultural crops worldwide. Conventionally the soil-borne pathogens and insects are kept in check by farm entrepreneurs by using soil fumigants as pre-planting treatment of soil. A fumigant is a chemical that, at a required temperature and pressure, can exist as a vapour or gas which when released penetrates objects or enclosed areas in concentrations. When applied at a high enough concentration for a long time, fumigants kill many kinds of soil organisms, thus disrupting plant growth and crop production. Concerns about the extensive use and negative environmental effects of chemical fumigants have led to the development of Biofumigation. The concept of Biofumigation is emerging as an increasingly feasible method of pest management practice in commercial agriculture because it can control agricultural crop pathogens and diseases without health and environmental risks. The process acts through the growth or incorporation of plant material into the soil which, throughout its degradation, releases glucosinolates that break down into nematotoxic isothiocyanates. Commonly used biofumigant plants include brown mustards, white mustards, radishes and rocket species. Also, sorghum (Sorghum bicolor) and sorghum-sudangrass (S. bicolor x, S. sudanense) cultivars with high content of dhurrin, a substance which is transformed into toxic hydrogen cyanide (also called prussic acid) are used as biofumigants.