Clue to pearl millet's heat tolerance may help fight climate chaos

Wednesday, 20 September 2017 08:10 GMT

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Heat resistance in crops will be crucial for many farmers as climate experts forecast major heat waves in years to come

Agriculture and climate experts have warned for some years now that rising temperatures and frequency of extreme climate events including heat waves experienced in many parts of the world will lead to a drop in major staple foods like maize or wheat.

One cereal stands out in this looming climate chaos: pearl millet. Now, the decoding and sequencing of the pearl millet genome by a global team of 65 scientists from 30 research institutions has revealed critical coping strategies.

The analysis of genetic variability among a thousand pearl millet lines has led to a better understanding of the ability of this dryland cereal to survive soaring temperatures (over 42 degrees Celsius) and its exceptional drought tolerance. This discovery, published in Nature Biotechnology on Sept 18, 2017, may also help develop climate adaptation strategies in other important cereal crops.

This drylands cereal, a staple in the Sahel and semi-arid India, has an extraordinary capacity to resist baking heat. While most cereals like rice or maize cannot support temperatures over 30 to maximum 35 degrees Celsius when they start forming their grain, pearl millet will fill its grain in air temperatures of up to 42 degrees.

Professor Rajeev Varshney, from the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), who coordinated the Pearl Millet Genome Sequencing Consortium explained: “We have found that compared to other cereals like wheat, rice or maize, pearl millet has a more diverse repertoire of genes for natural wax proteins, which act as thermal protection for the plant.”

A global research team across ten countries (India, China, France, USA, Germany, Austria, Senegal, Niger, Italy and UK) used the latest innovations in DNA sequencing and analysis to identify new genetic tools like molecular markers related to drought and heat tolerance, as well as other important traits (better nutrition profile, pest resistance).

With the recent advances in big data and statistical genetics, this research will catalyze breeding efforts to improve this crucial staple food for the food security and resilience of millions of people in arid and semi-arid Africa and Asia in particular.

Reliance on this climate resilient cereal for the dryland populations goes back centuries. Archaeologists have even found that despite recurrent droughts, millet-eating farmers  between the 11th and 15th century in Ghana, did not starve as their popular staple was pearl millet.

Pearl millet is a nutritious drylands cereal, rich in protein, fibre and essential micronutrients like iron, zinc and folate. Nutrition studies have shown that this cereal has the potential to fight iron deficiency, the most widespread micronutrient deficiency and major cause of anemia, affecting health and development of a third of global population. 

Pearl millet is grown on about 27 million hectares worldwide and is a daily food for more than 90 million people, among the most vulnerable in arid and semi-arid Africa and Asia. It is also an important source of fodder for millions of farms.

However, the plant’s yields have remained low over the last six decades, as this cereal is mainly grown in poor soil conditions without irrigation, minimal and no fertiliser and other agricultural inputs.

Investment in genetic research for this so-called “orphan” crop has been inadequate despite being the main food and feed for many farmers. As a result, breeders had limited genetic information to develop high yielding superior varieties and hybrids that respond to farmers’ constraints.

This new pearl millet genome research enables a better understanding of its genetic variability, and researchers have already identified candidate genes of very important traits, such as resistance to downy mildew, a very damaging millet disease, and heat tolerance.

Such crop heat resistance will be crucial for farmers in many parts of the world as climate experts forecast further heat waves in years to come. With the new biotechnology methods, we could foresee the transfer of such heat and drought tolerance to other important food cereals in a near future.

Professor M S Swaminathan, father of the Indian Green Revolution, has been a strong advocate for nutritious pearl millet, which is now included in the food basket of the Indian public distribution system in some Indian states, including Karnataka.

Unlocking the DNA data of this climate smart nutri-cereal will catalyse new pearl millet varieties to help in the drive for more productive, nutrition-sensitive and resilient farming.

Jerome Bossuet is co-head of communications and partnerships, International Crops Research Institute for the Semi-Arid Tropics (ICRISAT)