A nutrient-rich harvest

Satish Kumar Luthra's love for potatoes goes beyond the taste. As a potato breeder, he has developed 22 varieties that are not only suitable for various food-processing needs, such as making French fries, but also for cultivation in different locations. In 1989, when Luthra joined the Indian Council of Agricultural Research (ICAR)-Central Potato Research Institute (CPRI), Shimla, he was focused on developing high-yielding and disease-resistant varieties with good keeping qualities. Two decades later, however, Luthra decided to also breed for nutrition to fight "hidden hunger" – the lack of essential vitamins and minerals in the diet despite sufficient calorie intake.

Luthra's work benefited from a large seed bank of potato varieties stored at CPRI that helped him choose nutritious varieties as parents whose progeny could be propagated and selected for high nutrition. Breeding is a long and tedious process, especially in the case of potato as it is propagated via tubers. "We can produce only 8 to 10 tubers from one plant on an average, so it takes a lot of time to multiply the tubers to conduct the trials in a meaningful way," explains Luthra. It took Luthra 10-12 years to produce each potato variety.

His team's effort led to the release and notification of a purple-skinned, antioxidant-rich potato variety named Kufri Neelkanth in 2018; a red-skinned potato variety named Kufri Manik, rich in iron, zinc, anthocyanins and phenols, in 2021; and Kufri Jamunia, a purple-fleshed potato rich in Vitamin C, anthocyanins and carotenoids in 2024. These colourful varieties don't just tickle the taste buds but provide health benefits, too. Kufri Jamunia is currently being propagated under a breeder seed production programme. Kufri Neelkanth and Kufri Manik are already being grown by farmers but are expected to be seen in higher numbers in vegetable markets over the next five years.

A recent study in the journal Scientific Reports points out that though the Green Revolution ensured food security, it failed to provide nutritional security. The high-yielding varieties developed since have less of nutrients like iron and zinc, and more of toxic elements (bit.ly/nutritional-security). According to a 2023 report by the Food and Agricultural Organization (FAO), 74% of India's population could not afford a healthy diet, and 16.6% fell short of a nutrient-adequate one (bit.ly/India-undernourished).

To fight malnutrition, the Ministry of Health and Family Welfare has introduced food fortification schemes under which vitamins and minerals are added to common staple foods before distribution: iron, folic acid and Vitamin B-12 in rice and wheat flours; iodine in salt and so on. However, food fortification via nutrient addition suffers from distribution challenges and access to it depends on the processing facilities, and storage and transport infrastructure. Developing nutritious varieties through biofortification, however, is a one-time investment; it is a long-term approach that cuts the costs of buying the fortificants and obviates the need for an additional step of food processing. Scientists believe that nutrient-rich crops are also sturdier in the field and, therefore, biofortification in plants makes both the plant and the consumer healthy.

The demand for biofortified crops is also being driven by greater health awareness among consumers. "Earlier, nutritional traits were optional... or desired traits. Now, they are becoming must-have traits," says Pooran M. Gaur, Former Director of Research Program-Asia at the Hyderabad-based International Crops Research Institute for the Semi-Arid Tropics (ICRISAT). During 2014-2022, India released 87 biofortified varieties of 16 crops (bit.ly/biofortification-India), namely rice, wheat, maize, pearl millet, finger millet, small millet, lentil, groundnut, linseed, mustard, soybean, cauliflower, potato, sweet potato, greater yam and pomegranate.

The initial biofortification programmes worldwide focused on a few crops like rice, wheat and maize, and these were later expanded to all the major crops, fruits and vegetables. The focus also shifted from biofortifying crops with nutrients like iron, zinc and vitamin A to antioxidants, essential amino acids and healthy fatty acids, and from single-nutrient-rich crops to multi-nutrient crops that can provide nutrition in a single portion.

Scientists are now focusing on reducing anti-nutrients like lectins, saponins, oxalates and phytates, which hinder the absorption of nutrients. The ICAR-Indian Institute of Horticultural Research (IIHR), Bengaluru, has developed a low-oxalate spinach, and the ICAR-Directorate of Rapeseed-Mustard Research, Bharatpur, has developed a low-glucosinolate mustard (glucosinolates give plants their pungency). Regardless of the amount of iron present in wheat, millets or other seeded crops like rice, its bioavailability is no more than 2-5%, says Ajay Kumar Pandey, a plant molecular biologist at the National Agri-Food Biotechnology Institute (NABI), Mohali. "The bioavailability is low because most cereal crops have phytic acid."

Phytic acid (or phytate) binds to iron, zinc, manganese, calcium and other nutrients in the body, making them unavailable for absorption in the gut. However, crops require a small amount of phytic acid to complete their life cycle. Therefore, scientists are trying to develop crop varieties with low amounts of phytic acid. Pandey is trying to delineate the pathway of phytic acid production in wheat. He has found two crucial genes in this pathway – the ABCC13 transporter and Inositol Pentakisphosphate Kinase (IPK1) – and reduced their protein production via RNA interference technology in which small bits of RNA bind to IPK1 mRNA, stalling its protein production (bit.ly/phytic-acid). The team found that though blocking either of the two genes can reduce the phytic acid content of the plant, blocking IPK1 production is the preferred approach as it does not compromise other agro-economical traits. His team has been simultaneously working to identify the genes that are overexpressed when the plant has iron deficiency. If overexpressed, such genes can help extract more nutrients from the soil and load it in the plant.

There are two routes to developing a crop with desired traits: selective breeding to cross two parents with desired traits to get a progeny with superior traits, and genetic modification. Using gene editing, in 2020 a team led by Siddharth Tiwari at NABI developed a gene-edited banana variety that is rich in β-carotene, a type of provitamin A (bit.ly/biofortified-banana). This nutritious banana variety may soon undergo field trials in India. Pandey intends to use this technology to develop iron-rich, low-phytate wheat varieties that can be released in India. For this, he plans to reduce the production of phytic acid by reducing the expression of IPK1 gene in plants and simultaneously increase iron content in the same plant by overexpressing the genes that can help absorb more iron from the soil.

The availability of whole genome information of several crop plants and low-cost nucleotide sequencing have helped both breeders and plant biotechnologists to develop biofortified crops. The whole genome information allows plant biotechnologists to transfer the knowledge of nutrient-related genes and pathways obtained from one plant to another, and it gives opportunities to plant breeders to select better parents and develop better markers for selecting the progenies with desired traits.

"Once you have a reference plant genome... you are at a great advantage," says Firoz Hossain, Principal Scientist at ICAR-Indian Agricultural Research Institute, New Delhi. "You know the location of the gene, you know what is the exact length of the gene, what are the genes available at either side of the gene. This kind of information is really helpful."

Hossain's team developed and released a series of maize varieties that are rich in provitamin A and essential amino acids lysine and tryptophan in 2020. One such variety, 'Pusa HQPM-1 Improved', has 7.0 ppm of provitamin A as compared to 1-2 ppm in traditional hybrids. It also has high lysine (4.59%) and tryptophan (0.85%) in endosperm protein compared to traditional maize, which has 1.50-2.50% lysine and 0.30-0.40% tryptophan.

Nutrition, however, alone can't make a crop variety successful. "No farmer will ever grow any biofortified maize if it is not high-yielding," explains Hossain. Therefore, the nutritional varieties are only released if their yield is at par with existing non-nutritious varieties.

As the climate crisis worsens, developing nutritious, high-yielding crops that are also resistant to environmental stresses is key to ensuring food security.