On target with heat-tolerant
hybrid maize seed
deployment in South Asia

Millions of smallholders in South Asia make a living from maize, over 11 million farmers in India alone. However, less than 20% of the maize crop is irrigated, making it vulnerable to today’s warmer, drier and less predictable climate. Seed companies across South Asia now have the option of deploying high-yielding, heat stress-resilient maize hybrids developed by CIMMYT, which is meeting its targets for deploying the new heat-resilient maize seed suitable for hot, dry agroecologies of South Asia. A 2022 adoption study shows that under stressed conditions, the new hybrids enable smallholder farmers to harvest more, and improve their incomes.

Maize helps to support millions of farm families across South Asia. Over 80 percent of that grain is produced without irrigation, making the crop vulnerable to climate change, which is already bringing hotter weather and more frequent droughts to South Asia. Since 2012, CIMMYT’s Heat-Tolerant Maize for Asia (HTMA) project has worked with six government institutions and 22 private seed companies and farmer cooperatives in Bangladesh, Bhutan, India, Nepal, and Pakistan, creating new maize hybrids, based on elite, Asia-adapted germplasm from CIMMYT.

During Phase-1 (2012-2017), CIMMYT identified specific heat-stressed areas in South Asia, and established a heat stress phenotyping network. The work led to the identification of genomic regions and candidate genes that confer heat tolerance on maize. CIMMYT licensed 35 stress-tolerant maize hybrids to partners in South Asia, including the public sector and seed companies. CIMMYT also gave early generation improved maize lines to partners, so they could generate their own proprietary lines.
The new heat-tolerant maize hybrids developed by CIMMYT were deployed from 2018 to 2023. CIMMYT is partnering with 21 small and medium-sized seed companies in Bangladesh, India, Nepal and Pakistan, besides Corteva Agrosciences, to develop a pipeline of improved heat-tolerant maize hybrids available to smallholder farmers.
During the scaling out of improved seed, CIMMYT has been particularly targeting women and vulnerable groups using on-farm demos, field days (many especially for women), small seed packs, and multimedia. Women have appreciated the new hybrids as the plants stay green longer, and provide better fodder for livestock during the lean season.
By 2022, 20 high-yielding, heat-tolerant hybrids have been officially released in South Asia, including Bangladesh (5), Bhutan (1), India (8), Nepal (3), and Pakistan (3). These hybrids have been planted on an estimated 50,000 hectares. Nepal, which was once dependent on its neighbors for 90% of its hybrid maize seed, is now becoming self-sufficient.
About 1000 metric tons of heat-tolerant maize seed was distributed to smallholder farmers in South Asia by 2022, slightly above CIMMYT’s target, as shown in this Figure. According to, P. H. Zaidi, leader of CIMMYT’s HTMA project, “We have enjoyed excellent support from government agencies, who realize the urgency of adapting to climate change. Close cooperation with seed companies has also been crucial. The increasing demand for this seed from the farmers has also helped all the stakeholders to stay on target. The farmers are now increasingly aware that climate change is a reality, and we need innovations to adapt to it.”

A heat-tolerant hybrid (CAH153, extreme right) and popular commercial hybrids severely damaged by fall armyworm in demo field, Hyderabad, India. ©CIMMYT.

Studies in India (Karnataka and Odisha states) and in Nepal (the Terai region) showed that the heat-tolerant maize hybrids out-performed the commercial hybrids currently on the market, especially under drought and heat stress. For example, in a 2022 study of 180 maize farmers in Karnataka, published in Frontiers in Sustainable Food Systems, under optimum conditions, the stress-tolerant maize hybrids performed at par with the commercial hybrids. However, under stressed conditions, the new hybrids made a huge difference. Smallholders increased their yields from two tons per hectare to three tons per hectare when they planted the stress-tolerant hybrids from CIMMYT. As an added benefit, under severe drought conditions, the heat-tolerant hybrids yielded larger grains and ears than commercial hybrids, so farmers could sell the new maize for an additional $10 per ton ($216 vs $206). According to the study’s lead author, CIMMYT scientist Atul P. Kulkarni, “Farmers who planted the CIMMYT hybrid earned $148 per hectare more than the non-adopters, who did not even recover their investment. In a drought year, in a rainfed environment, non-adopters lost on average $31 per hectare.” Kulkarni goes on to say, “The farmers who adopted the new maize hybrids were very much like their neighbors who did not plant the new seed. The adopters and the others were of similar ages and educational backgrounds. The adopters were not simply the richest farmers. The non-adopters even planted slightly more land to maize than the adopters.”

The biggest difference between the two groups of farmers is that those who saw the new hybrids at a field day were about a third more likely than their peers to plant the stress-tolerant maize. “This means that just making farmers aware of the new stress-tolerant hybrid maize will encourage many of them to try it out,” says Kulkarni.

Certified seed deployment in South Asia.

Genotypic variability for heat and drought-tolerance at harvest. ©CIMMYT.

Seed company representatives examine heat-tolerant maize at a demo in Raichur, India. ©UAS Raichur.

In South Asia, over 80 percent of maize grain is produced without irrigation.

About 1000 metric tons of heat-tolerant maize seed was distributed to smallholder farmers in South Asia by 2022.