Combating micronutrient malnutrition: identification of commercial sorghum cultivars with high grain iron and zinc.

Abstract

Sorghum (Sorghum bicolor) is the fifth most important cereal crop grown on 47 million ha in 104 countries in Africa, Asia, Oceania and the Americas. The United States, Nigeria, India, Mexico, Sudan, China and Argentina are the major sorghum producers globally (http://faostat.fao.org/site/567/default.aspx#ancor accessed on 14 September 2010). Sorghum, a heat and drought tolerant C4 plant, is a widely consumed cereal staple in subtropical and semi-arid regions of Africa and Asia (Kresovich et al. 2005, Reddy et al. 2009). It is the second cheapest source of energy and micronutrients [after pearl millet (Pennisetum glaucum)]; and a vast majority of the population in Africa and central India depend on sorghum for their dietary energy and micronutrient requirement (Parthasarathy Rao et al. 2006). Limited studies indicated that mineral concentrations and bioavailability are limited in cooked sorghum grain (Kayode et al. 2006); but this needs to be further validated. Micronutrient malnutrition, primarily the result of diets poor in bio-available vitamins and minerals, causes blindness and anemia (even death) in more than half of the world’s population, especially among women of reproductive age, pregnant and lactating women and preschool children (Underwood 2000, Sharma 2003, Welch and Graham 2004) and efforts are being made to provide fortified foods to the vulnerable groups of the society. Biofortification, where possible, is the most costeffective and sustainable solution for tackling micronutrient deficiencies as the intake of micronutrients is on a continuing basis with no additional costs to the consumer in the developing countries in arid tropics and subtropics. Biofortification of sorghum by increasing mineral micronutrients [especially iron (Fe) and zinc (Zn)] in the grains is of widespread interest (Pfeiffer and McClafferty 2007, Zhao 2008, Ashok Kumar et al. 2009). The International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) is working on sorghum biofortification for enhancing the grain Fe and Zn contents. Preliminary studies by Reddy et al. (2005) indicated limited variability for grain Fe and Zn contents in sorghum hybrid parents, advanced breeding lines and germplasm accessions. A field study conducted at ICRISAT farm in Patancheru, India to enhance the grain Fe and Zn under balanced nutrient application [nitrogen (N), phosphorus (P), potassium (K) along with sulfur (S), boron (B), Fe and Zn were applied to the soil] did not increase the grain Fe and Zn contents probably because the inherent availability of these nutrients in the soil was not limiting. Genetic enhancement is in progress to develop high Fe and Zn containing cultivars with desired agronomic background. While it is in progress, an attempt was made to assess the variability in the commercial sorghum cultivars that are currently being cultivated by the farmers in India. Identification of high grain Fe and Zn commercial cultivars would help in expanded dissemination of the cultivars to complement the ongoing efforts for combating the micronutrient malnutrition.