India’s approval of its first genetically modified food crop — the herbicide-tolerant (HT) mustard hybrid DMH-11 — marks a historic shift in agricultural policy, but agronomists and plant scientists are warning that the technology alone will not boost farmer incomes or oilseed production unless it is part of a broader, more diverse farming strategy .
Without careful integration into existing crop rotations, the over-reliance on a single herbicide could accelerate weed resistance, damage soil health, and leave farmers with higher input costs and lower profits in the long run .
The Promise of DMH-11
Mustard is a self-pollinating crop. To develop DMH-11, scientists at the University of Delhi deployed a genetic system using three transgenes — barnase, barstar, and bar. The bar gene confers resistance to the herbicide glufosinate ammonium (Basta), while the barnase-barstar system enables the production of high-yielding hybrid seeds that remain fertile for farmers .
Field trials conducted by ICAR across eight locations showed DMH-11 had an average yield advantage of 28 per cent over the popular variety Varuna and 37 per cent over zonal checks . Given that India imports nearly 55–60 per cent of its edible oil consumption, proponents argue that homegrown high-yielding hybrids could reduce this dependency and save significant foreign exchange .
The Risk: A Herbicide Trap
Despite these advantages, experts caution that planting HT crops without a diversified weed management plan is a recipe for disaster. In intensive farming systems globally, the repeated use of the same herbicide has led to the rapid evolution of resistant weeds, or “superweeds,” forcing farmers to apply higher doses or more toxic chemicals .
Weed management experts from the ICAR-Directorate of Weed Research note that while HT crops can cut weeding costs and reduce labour drudgery — particularly for women — their sustainability depends entirely on careful management .
The primary risk is “selection pressure.” If the same herbicide is used repeatedly across vast areas without rotation, it kills susceptible weeds but leaves naturally resistant individuals to multiply, eventually rendering the technology useless .
The Solution: Integrated Weed Management (IWM)
To mitigate these risks, agricultural scientists advocate for a shift from herbicide-based control to Integrated Weed Management (IWM) . This involves combining chemical control with a suite of other agronomic practices:
Rotate crops and herbicides: Farmers should not grow HT mustard continuously in the same field. Introducing pulses (chickpea, lentil), other oilseeds, or cereals into the rotation allows the use of different herbicide groups, reducing the chance of any single weed population developing resistance .
Maintain crop competition: Optimizing seeding rates and row spacing can create a dense crop canopy that naturally suppresses weeds through competition for light, water, and nutrients, reducing the need for chemical intervention .
Physical and mechanical controls: Practices like strategic tillage (where suitable) and the use of weed seed impact mills at harvest can destroy weed seeds before they re-enter the soil seed bank .
Monitor and test: The best strategies rely on data. Regular field monitoring for weed escapes and soil testing for resistant biotypes allow farmers to adapt their strategies pre-emptively rather than reacting to a crisis .
From Single Solution to Systems Change
For Indian policymakers and extension services, the lesson is clear: herbicide-tolerant crops are tools, not solutions. Research shows that acting pre-emptively to diversify rotations is financially viable, whereas trying to retrofit diversity after resistance has evolved is costly and often unsuccessful .
The EU’s recent recommendations for herbicide-tolerant crops stress that whether a crop is genetically modified or conventionally bred, it poses the same agronomic risks and therefore requires the same diverse management strategies, including mandatory rotation plans and farmer education .
The Road Ahead
As state agricultural universities and ICAR prepare to conduct large-scale demonstrations of DMH-11 across the mustard belt, the focus must shift from production alone to long-term stewardship . This includes:
- Capacity building: Training farmers to integrate HT crops into diverse rotations rather than treating them as a standalone solution.
- Policy support: Incentivizing crop diversification to ensure that the adoption of HT mustard does not come at the cost of biodiversity or lead to monocultures.
- Stewardship programs: Mandating product labeling and grower guidelines that explicitly outline resistance management plans, similar to those used for Bt cotton .
DMH-11 represents a major technological leap, but its success will ultimately be determined not by yield data from controlled plots, but by the agronomic wisdom with which it is deployed in the diverse, complex ecosystems of India’s farms.
