Rice, domesticated by humans over 10,000 years ago has now become the staple food for more than three billion people. But today’s rice does not have the same density of essential nutrients as those cultivated 50 years ago, notes a new study . Researchers from various institutes under the Indian Council of Agricultural Research (ICAR) and Bidhan Chandra Krishi Viswavidyalaya found depleting trends in grain density of zinc and iron in rice and wheat cultivated in India. The findings were published last month in Environmental and Experimental Botany.
The team collected seeds of rice (16 varieties) and wheat (18 varieties) from the gene bank maintained at the ICAR-National Rice Research Institute, Chinsurah Rice Research Station and ICAR-Indian Institute of Wheat and Barley Research.
Cultivar repositories
“These are nodal institutes that preserve and archive the old cultivars or varieties from our country. These institutes are repositories of genetic materials. If you want to study the genuine variety, or as botanists call them, ‘the true type’ of a plant, these institutes are your source,” explains Professor Biswapati Mandal from the Bidhan Chandra Krishi Viswavidyalaya, West Bengal, and one of the corresponding authors of the paper.
The collected seeds were germinated in the laboratory, sown in pots and kept under an ambient environment outdoors. They were treated with the necessary fertilizers and the post-harvest seeds were studied for their nutrient content.
Falling nutrients
The team noted that zinc and iron concentrations in grains of rice cultivars released in the 1960s were 27.1 mg/kg and 59.8 mg/kg. This depleted to 20.6 mg/kg and 43.1 mg/kg, respectively in the 2000s. In wheat, the concentrations of zinc and iron --- 33.3 mg/kg and 57.6 mg/kg in cultivars of the 1960s, dropped to 23.5 mg/kg and 46.4 mg/kg, respectively in cultivars released during the 2010s.
Sovan Debnath, the first author of the paper explains: “There could be several possible reasons for such depletion: one is a 'dilution effect' that is caused by decreased nutrient concentration in response to higher grain yield. This means the rate of yield increase is not compensated by the rate of nutrient take-up by the plants. Also, the soils supporting plants could be low in plant-available nutrients.” He is a doctoral researcher at Bidhan Chandra Krishi Viswavidyalaya and a scientist for ICAR.
“Zinc and iron deficiency affects billions of people globally and the countries with this deficiency have diets composed mainly of rice, wheat, corn, and barley. Though the Indian government has taken initiatives such as providing supplementation pills to school children, it is not enough. We need to concentrate on other options like biofortification, where we breed food crops that are rich in micronutrients,” he adds.
Not sustainable
The paper concludes that “growing newer-released (1990s and later) cultivars of rice and wheat cannot be a sustainable option to alleviate zinc and iron malnutrition in Indian population. These negative effects need to be circumvented by improving the grain ionome (that is, nutritional make-up)…while releasing cultivars in future breeding programmes”
