Gene-Edited Mustard: Less Pungent, More Useful

Why in News?

• Indian scientists have developed the first ever low-pungent mustard that is pest and disease-resistant.
• The new breakthrough can be used to address the challenges associated with the traditionally grown oil seeds.

 

India’s Traditional Domestically Grown Oil Seed

• India’s most significant domestically-grown oilseed is rapeseed-mustard.
• Its share in the country’s production of vegetable oils has been estimated at 42.6% (more than soyabean’s 19.2%) and in that of meal at 30.3% (next to soyabean’s 38.9%),for the marketing year ending September 2023.
• Oilseeds do not just yield oil for cooking, the residual cake after extraction of oil from the seeds is a protein-rich ingredient used in livestock, poultry, and aqua feed.

 

Problems Associated with Traditionally Grown Rapeseed-Mustard

• High Levels of Glucosinolates
  • Mustard seeds have high levels of glucosinolates, a group of sulphur and nitrogen-containing compounds contributing to the characteristic pungency of their oil and meal.
  • The high level of Glucosinoates limits the oil’s acceptability among consumers – especially those preferring medium cooking.
• Problem with Residue Cake
  • The problem is even more with the meal. Rapeseed meal is indigestible to poultry and pigs, while having to be mixed with fodder grass and water for giving to cattle and buffaloes.
  • Besides reducing their feed intake, high glucosinolates are also known to cause goiter (swelling of neck) and internal organ abnormalities in livestock.

 

The Research on Canola Quality Mustard

• To address the problems of traditionally grown mustard seeds, a lot of effort in the past two decades has gone into the breeding of rapeseed-mustard of Canola quality.
• The research has been done by scientists at Delhi University’s Centre for Genetic Manipulation of Crop Plants (CGMCP) and the Indian Council of Agricultural Research.

 

How Canola-Quality is Different from Traditionally Grown Rapeseed-Mustard

• Lower Glucosilolates:The dry seeds from the normal mustard (Brassica juncea) cultivated in India contain 120-130 parts per million (ppm or mg/kg) of glucosinolates. This is as against the sub-30 ppm levels in canola seeds.
• Less Pungency: By lowering the glucosinolate content to the same dry seed weight concentration, the scientists have bred mustard lines whose oil and meal match the standard of canola-quality rapeseed (Brassica napus) in terms of pungency.

 

Challenges Faced by Canola-Quality Mustard Seeds

• Issue of Large-Scale Cultivation: Despite having low levels of glucosinolates, large-scale cultivation of these canola-quality has not taken place.
• Vulnerability to Pests and Diseases
• A major reason why canola-quality seeds are not popular is their vulnerability to pests and diseases.
• While the lowering of glucosinolate levels in seed is desirable for oil and meal, a related reduction in the whole plant weakens its defence.

 

The New Breakthrough: A Gene-Edited Mustard

• In the new research, Glucosinolates are synthesised in the leaves and pod walls of mustard plants.
• Their translocation and accumulation in the seeds happens through the action of glucosinolate transporter or GTR genes.
• There are 12 such genes under two distinct classes of GTR1 and GTR2with six copies each.
• The researchers have edited 10 out of the 12 GTR genes in ‘Varuna’, a high-yielding Indian mustard variety.
• For this, they used CRISPR/Cas9 – a gene-editing tool deploying an enzyme, which acts as a molecular scissors to cut the DNA at precise targeted locations of the gene, and then letting the natural DNA repair process to take over.
• The researchers have used CRISPR/Cas9 editing to create mutations and change the nucleoide or basic building block sequence of the DNA in the 10 target GTR genes.
• By doing this, their encoded proteins, responsible for transport of the glucosinolates to the seeds, were rendered non-functional.

 

Advantage of the Gene-Edited Mustard

• Balanced Quantity of Glucosinolates
  • The seeds of the resultant targeted genes-edited Varuna mustard variety had glucosinolate content well below the 30-ppm canola-quality threshold.
  • At the same time, the other plant parts, especially the leaves and pod walls enclosing the seeds, had significantly higher glucosinolate accumulation.
• High Resistance Against Pests and Diseases
  • The GTR-edited low-seed high-leaf glucosinolate lines were tested for resistance against the virulent fungal pathogen Sclerotinia sclerotiorumand the insect pest Spodoptera litura.
  • The edited lines displayed defence response against these at par with or better than that of the wild-type mustard.
  • The higher glucosinolate concentration in the leaves and pod walls, due to their impaired transport to the seeds, clearly had a role.

 

The Difference Between GM (Gene Modified) and GE (Gene Edited) Crops

• GE Mustard is Transgene-Free
  • The new GTR genes-edited mustard lines are transgene-free or non-genetically modified (GM).
  • They contain no foreign genes like those of the Bacillus thuringiensisbacteria in cotton or Bar-Barnase-Barstar (isolated from other soil bacteria) in the GM hybrid mustard (DMH-11) bred by CGMCP scientists.
  • The low-seed high-leaf glucosinolate mustard lines developed are genome edited or GE, as opposed to GM or transgenic plants.
  • While the Cas9 enzyme, derived from the Streptococcus pyogenesbacteria, was used to cut the DNA of the targeted genes in the first-generation plants, this protein is segregated out in the subsequent generations.
  • The final GE lines contain no Cas9 protein and are transgene-free.
• Exemption for GE Plants from GEAC Approval
  • GM crops are currently subjected to stringent “environmental release” regulations in India, not just for commercial cultivation but even field trials and seed production.
  • Such release is contingent upon clearance from a special Genetic Engineering Appraisal Committee (GEAC) under the Ministry of Environment, Forest and Climate Change (MoEFCC).
  • Recently,the MoEFCC exempted GE plants “free of exogenous introduced DNA” from the requirement of GEAC approval for open field trials leading to commercial release.
  • Such clearance is now necessary only at the level of an Institutional Bio-safety Committee (IBSC), comprising scientists from the institutions engaged in the GE crop development and from the DBT.

 

Importance of the New Breakthrough

• Can Reduce the Import Dependency of Edible Oils
  • India is a huge importer of edible oils. These imports were valued at $20.84 billion (Rs 167,270 crore) during the fiscal year ended March 2023, while meeting over 60% of the country’s consumption requirement.
  • GM hybrid mustard and the new GE low-seed high-leaf glucosinolate lines are major plant breeding advancements from Indian scientists that can go some way towards bringing down the dependence on imported vegetable oils.
• Can Increase the Crop Yield and Product Quality
  • Mustard and soyabean are India’s most widely-cultivated oilseed crops, planted annually on 9 million and 12.5 million hectares area respectively.
  • Its higher average oil extractable content (38% versus 18% for soyabean) makes mustard the bigger “oilseed” crop, while a source of both fat for humans and protein for animals.
  • Given the massive foreign exchange outgo on account of imports, there is in a dire need to boost domestic oilseeds production through focused breeding for improving crop yields, pest and disease resistance, and product quality.

 

Conclusion

• The new Gene-Edited Mustard created by Indian Scientists is a significant achievement in Indian agriculture sector.
• This new breakthrough has the potential to reduce India’s dependency on vegetable oil imports, increase crop yields and bring a significant change to the product quality.

 

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Q1) How has GM crops evolved in India?

First GM crop was released under Vajpayee government with the slogan of Jai Vigyan. Indian farmers started cultivating Bt cotton, a pest-resistant, GM version of cotton, in 2002-03. Bt modification is a type of genetic modification where the Bt gene obtained from the soil bacterium Bacillus thuringiensis is introduced into the target crop - in this case, cotton. Bt cotton is resistant to bollworm, a pest that destroys cotton plants. By 2014, around 96% of the area under cotton cultivation in India was Bt cotton, making India the fourth-largest cultivator of GM crops by acreage and the second largest producer of cotton.

 

Q2) What is GEAC?

The Genetic Engineering Appraisal Committee (GEAC), under the Ministry of Environment, Forest and Climate Change (MoEF&CC), is responsible for the assessment of proposals related to the release of genetically engineered organisms and products into the environment, including experimental field trials. GEAC or people authorised by it have the power to take punitive actions under the Environment Protection Act.

 

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Source: The Indian Express