Q.26 Which of the following is one of the possible hazards of genetically modified (GM) crops?

1. Modified genes of herbicide resistance from GM crops get into weed plants through
   pollination and this plant might become resistant to herbicide and so become a
   “Superweed”.
2. There is no possible hazard known till date, regarding transfer of any genes between the plants.
3. Production techniques of GM crops is proof and genetic engineering offers the advantage
   of transferring only those genes that are required.
4. Production of GM crops may replace the existing germplasm.

   GM Crops Hazard: Superweed Formation via Gene Transfer

   Modified herbicide resistance genes from GM crops can transfer to weeds through pollination, creating herbicide-resistant “superweeds.” This makes the first statement the correct identification of a possible hazard.

   Introduction

   Hazards of genetically modified GM crops include the real risk of herbicide resistance genes transferring to weeds via pollination, creating unstoppable “superweeds.” While GM technology offers benefits, this gene flow represents a documented ecological concern. This guide evaluates each statement for exam accuracy.

   Statement Analysis

   Superweed Reality: 27 glyphosate-resistant weed species documented globally; 75% first appeared post-GM HT crop adoption (1996).

   • Modified genes of herbicide resistance from GM crops get into weed plants through pollination creating “Superweed”: Correct hazard. Gene flow via pollen: canola → wild mustard, rice → red rice. Creates weeds requiring 2-3× herbicide or tillage.

   • There is no possible hazard known till date regarding transfer of any genes between plants: Incorrect. Documented cases: GM creeping bentgrass → wild relatives; Bt maize → Mexican landraces. Gene flow occurs naturally via pollen/wind.​

   • Production techniques of GM crops is foolproof and genetic engineering offers advantage of transferring only required genes: Incorrect/misleading. No technique 100% prevents gene flow; promoters (CaMV 35S) can silence/activate unexpectedly. Fitness costs exist.​

   • Production of GM crops may replace existing germplasm: Not primary hazard. Market-driven replacement ≠ biological hazard; genebanks preserve germplasm. Superweeds directly threaten agriculture.​

   Superweed Mechanism

   text

   GM Crop (Roundup Ready) ──Pollen──→ Compatible Weed
Glyphosate resistance gene integrates → Superweed survives spraying


   Examples: Palmer amaranth, waterhemp, horseweed, giant ragweed; 2.5M acres US affected.​

   Resistance	Weeds Affected	Solution Cost
   Glyphosate	27 species	+25% herbicide use
   Multiple	9 species	Tillage + diversified MOAs ​

   Risk Mitigation Strategies

   • Gene containment: Maternal inheritance, pollen sterility

   • Management: Rotate herbicides/MOAs, cover crops

   • Stacking: 2,4-D + glyphosate tolerance (controversial)​

   Exam Relevance

   GATE Life Sciences: Recognize superweed risk as legitimate GM concern vs. theoretical benefits. Key: Herbicide-tolerant GM → selection pressure → resistant weeds. Mnemonic: “GM Herbicide genes → Pollinating Problems.”​