Department of Biotechnology, Ministry of Science & Technology, Government of India, New Delhi, India.
Plant tissue culture technology offers great promise for the production of quality planting material on account of disease free and true to type plants produced through micropropagation techniques. The need for a certification programme for the tissue culture plants is imperative since inadvertent micropropagation of virus infected plants will not only result in poor stand, but also in undesirable spread of viruses wherever such plants are grown. Also, failure to use prescribed standard protocols will result in variations in the plants produced. The most deleterious variants in tissue culture raised plants are those that effect yield, genetic fidelity and carry infection of viruses, which are difficult to diagnose. This is an area of great concern, and requires a well-structured system be put in place to provide support to the tissue culture industry for the commercialization of tested virus free, high genetic fidelity planting material.
A large number of viruses infect horticultural, plantation and forest plants which are being micropropagated by the tissue culture industry. Generation of virus-free planting material is an ideal strategy to confine these viruses and also to facilitate the movement of materials across the domestic and international boundaries. Tissue culture is an useful approach for generating virus-free planting material. In order to minimise the risk of inadvertent propagation of virus infected plants and introduction of somaclonal variability, the tissue culture raised plants need to be thoroughly indexed for freedom from viruses and checked for quality. Careful indexing based on recent biotechnological methods such as imunoprobes, nucleic acid probes and polymerase chain reaction (PCR) would ensure phytosanitary safety during the movement of planting materials. Similarly, molecular testing will ensure quality control. The test for virus and quality will have direct impact on developing a vibrant tissue culture industry as the demand for certified tissue culture raised plants will grow exponentially. The country has expertise to undertake diagnosis of plant viral diseases through the application of biophysical, immunological and molecular techniques. Immunodiagnosis is the most useful technique using polyclonal and monoclonal antibodies raised against viruses. Polyclonal antibodies are now available in the country for various groups of viruses like potyviruses, tospoviruses, tobamoviruses, potexviruses, luteoviruses, badnaviruses, closteroviruses, etc. These polyclonal antibodies have been very useful in the specific identification of viruses and their strains, and for plant virus diagnosis. The technology for the production of monoclonal antibodies is also available in the country, but their production has not caught up to the desired level for plant viruses due the lack of adequate facilities. The viruses for which diagnostic probes (antibodies and cDNA probes) have been developed are known to infect a variety of plant species like: banana, brinjal, cassava, citrus, Frenchbean, garlic, gladioli, groundnut, lilies, mungbean, onion, rice, soybean, sugarcane, tobacco, tomato, urdbean, ornamental plants etc. Accordingly a National Certification System for Tissue Culture Plants (NCS-TCP) has been developed for the first time, not only in the Country but also globally, where currently no such organized structure exists for certification of Tissue Culture material. This system is now operational and Referral Centers and Accredited laboratories have been established.
