India gets first herbicide-tolerant & non-GM rice varieties

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In news- The Indian Agricultural Research Institute (IARI) has developed the country’s first-ever non-GM (genetically modified) herbicide-tolerant rice varieties. 

About the new rice varieties-

• The varieties – Pusa Basmati 1979 and Pusa Basmati 1985, contain a mutated acetolactate synthase (ALS) gene.
• Water is a natural herbicide that takes care of weeds in the paddy crop’s early-growth period. 
• The new varieties simply replace water with Imazethapyr, a broad-spectrum herbicide, to control weeds.
• Hence there’s no need for nursery, puddling, transplanting and flooding of fields.
• They can be directly seeded and significantly save water input and labour compared to conventional transplanting.

• Imazethapyr, effective against a range of broadleaf, grassy and sedge weeds, can’t be used on normal paddy, as the chemical does not distinguish between the crop and the invasive plants. 
• The ALS gene in rice codes for an enzyme (protein) that synthesises amino acids for crop growth and development. 
• The herbicide sprayed on normal rice plants binds itself to the ALS enzymes, inhibiting their production of amino acids.

• The new basmati varieties contain an ALS gene whose DNA sequence has been altered using ethyl methanesulfonate, a chemical mutant. 
• As a result, the ALS enzymes no longer have binding sites for Imazethapyr and amino acid synthesis isn’t inhibited. 
• The plants can also now “tolerate” application of the herbicide, and hence it kills only the weeds.
• This is herbicide-tolerance through mutation breeding, not by Genetic modification (GM) to ensure no foreign gene in the new varieties. 

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