Seed Health Management for Better Productivity - Govind Ballabh ...

(Seed Health Management for Better Productivity)seed quality. Molecular diagnostics based on immunological and DNA techniques can provide aneasy-art-technology for disease surveillance and disease forecasting. Testing for and monitoring ofpathogens is a component of seed quality control. For current seed health testing, seed-bornepathogens are usually recovered by conventional agar plating, blotter tests or by serologicaltechniques. These traditional methods of detection and identification are often time consuming andlabor intensive. Over the past decade, considerable advancement has taken place in thedevelopment of molecular diagnostics for detection of pathogens in seeds. Potential benefits(rapid, same-day analysis specific and sensitive tests) this new technology offers make itextremely attractive. The recent and rapid pace of developments in molecular biology has providednew opportunities in diagnostic areas.Modern diagnostic methods are based on high affinity biomolecular interaction betweenligand and binder. These include the nucleic acid hybridization (DNA based) and antibody basedtechniques involving complementary interaction of DNA-DNA, DNA-RNA, RNA-RNA and antigen–antibody (Ag–Ab) interactions that have been applied to KB diagnostics and pathogen detection atthe field level.Sample preparation in diagnosticsThe foremost element to be taken into account in the development and application ofanalytical methods in plant diagnostics is the sample preparation. Discussion of some of thesemethods is relevant at this stage because many of them are distinguished by the relative lack ofsample preparation required before the analysis can be performed. However, some methods dorequire the sample preparation for biological amplification. The biological amplification consists ofextraction stage and culture of pathogen on an enriched medium. Table 1 summarizes attributes tobe considered in the primary selection of diagnostic methods for seed borne plant pathogens.Extraction of seed-borne pathogensSeveral methods of seed-borne pathogens isolation are a modification of general seedwash assays and being currently used by most international seed health laboratories, that havebeen improved by the incorporation of suitable detergents commonly used for extracting fungi fromsoil.Detection techniques based on cellular and molecular differencesFor differentiating one from other pathogens many techniques can be employed. Thepresent methods for testing grain for the presence of seed borne pathogens include microscopicanalysis, pathogenicity tests; isozyme analysis that identifies disease causing entities. However,the procedures have many drawbacks as they rely on individual examiners and are highlysubjective in their nature. The techniques include conventional techniques, biophysical, isozymeand DNA based marker and immunological techniques.- 181 -