First Herbicide-tolerant & Non-GM rice varieties

In News 

• Recently, the Prime Minister of India officially released new varieties of rice named ‘Pusa Basmati 1979 ‘and ‘Pusa Basmati 1985’.

About 

• The Indian Agricultural Research Institute (IARI) developed the country’s first-ever non-GM (genetically modified) herbicide-tolerant rice varieties.
• The varieties contain a mutated acetolactate synthase (ALS) gene making it possible for farmers to spray Imazethapyr, a broad-spectrum herbicide, to control weeds. 
• These varieties can be directly seeded and significantly save water and labour compared to conventional transplanting.
• Development: Both Pusa Basmati 1979 and 1985 have been bred by crossing existing popular varieties — Pusa 1121 and Pusa 1509, respectively — with ‘Robin’. 
  • The latter is a mutant line derived from Nagina 22, an upland drought-tolerant rice variety. The mutant was identified for Imazethapyr-tolerance by S Robin, a rice breeder from Tamil Nadu Agricultural University in Coimbatore.

Significance and need

• Paddy transplantation is both labour- and water-intensive. The field where the seedlings are transplanted has to be “puddled” or tilled in standing water. 
  • For the first three weeks or so after transplanting, the plants are irrigated almost daily to maintain a water depth of 4-5 cm. 
• Farmers continue giving water every two to three days even for the next four-five weeks when the crop is in tillering (stem development) stage.
• 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 and there’s no need for nursery, puddling, transplanting and flooding of fields.

What is Direct Seeding of Rice (DSR)?

• It is a method under which pre-germinated seeds are directly drilled into the field by a tractor-powered machine.
• There is no nursery preparation or transplantation involved in this method. 
• This water is replaced by real chemical herbicides and farmers have to only level their land and give one pre-sowing irrigation.
• The Punjab Agricultural University (PAU) in Ludhiana has developed a ‘Lucky Seed Drill’ that can both sow seeds and simultaneously spray herbicides to control weeds. 

Advantages 

• Water savings because the first irrigation (apart from the pre-sowing rain) under DSR is necessary only 21 days after sowing. 
• Less requirement of labour.  
• Reduction in methane emissions and global warming potential
• Little disturbance to soil structure
• Enhanced system productivity

Disadvantage 

• The main issue is the availability of herbicides.
• The seed requirement for DSR is also higher than transplanting. 
•  Land levelling is compulsory in DSR, therefore, increases the cost.
• In the DSR technique plants have to come out properly before the monsoon rains arrive, early sowing is required.
• The DSR method is not suitable on certain types of soil and in such fields only transplanting methods work.

Difference Between DSR & Normal Transplantation

• In transplanting, farmers prepare nurseries where the paddy seeds are first sown and raised into young plants. These seedlings are then uprooted and replanted 25-35 days later in the main field.

Present Status of direct seeding of rice 

• The government is promoting DSR during the Kharif season this year to conserve 10 to 15 per cent of irrigation water as compared to the puddle transplanted rice. 
• The promotion of DSR will lead to the conservation of groundwater, therefore, reduced power consumption and save farmers from a labour shortage. 
• Farmers in Punjab and Haryana are already adopting direct seeding of rice (DSR) in response to labour shortages and depleting water tables. This year alone, roughly 6 lakh of the total 44.3 lakh hectares area under paddy in the two states has come under DSR.
• DSR cultivation is currently based on two herbicides, Pendimethalin (applied within 72 hours of sowing) and Bispyribac-sodium (after 18-20 days).
  • These are costlier than Imazethapyr (Rs 1,500 versus Rs 300/acre). Imazethapyr, moreover, has a wider weed-control range and is safer, as the ALS gene isn’t present in humans and mammals. Even in the herbicide-tolerant rice, the chemical will target only the weeds.”
• Transplantation in paddy typically requires about 30 irrigations, each consuming some 5 hectare-cm of water (one hectare-cm equal 100,000 litres). Puddling alone takes up about 15 hectare-cm. 
• In all, DSR is estimated to need 30 per cent less water, save Rs 3,000 per acre in transplantation labour charges, and also 10-15 days’ time due to no nursery preparation.

Source: IE