India- The Indian Agricultural Research Institute (IARI) has developed the country’s first-ever non-GM (genetically modified) herbicide-tolerant rice varieties . Farmers can directly seed this and significantly save water and labour compared to conventional transplanting.
The varieties — Pusa Basmati 1979 and Pusa Basmati 1985 — contain a mutated acetolactate synthase (ALS) gene. This makes it possible for farmers to spray Imazethapyr, a broad-spectrum herbicide, to control weeds. This dispenses with the need to prepare nurseries where paddy seeds are first raised into young plants. This is before uprooting and replanting 25-35 days later in the main field in India.
Paddy transplantation is both labour- and water-intensive. For the first three weeks or so after transplanting, farmers irrigate daily to maintain a water depth of 4-5 cm. Farmers continue giving water every two-three days. This is even for the next four-five weeks when the crop is in tillering (stem development) stage even in India.
“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. You can sow paddy directly, just like wheat,” said A K Singh, director of IARI.
The new basmati varieties contain an ALS gene whose DNA sequence scientists 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 GM. There isn’t any foreign gene here,”says Singh.
Both Pusa Basmati 1979 and 1985 have been bred by crossing existing popular varieties in India . Namely Pusa 1121 and Pusa 1509, respectively — with ‘Robin’. The latter is a mutant line from Nagina 22, an upland drought-tolerant rice variety. Image credits: unsplash