Drought-tolerant crops

Also known as Drought-tolerant maize, HB4 wheat, HB4 drought-tolerant soybean, Stress-tolerant maize

Crop varieties bred or engineered to keep yields up when rain is short. Conventionally bred drought-tolerant maize is in use in parts of sub-Saharan Africa, while the transgenic HB4 wheat and soybean have regulatory approvals in several countries but limited evidence of farm-scale performance.

Pilot and early commercialReported, unverifiedReviewed 22 Oct 2026
AI illustration · Illustrative scene, not a photograph of the specific device or experiment.

In plain language

Drought can cut a harvest sharply, especially when it hits while the plant is flowering or filling its grain. Plant breeders have long selected for varieties that keep producing when water is short. Drought-tolerant varieties do not stop yield loss altogether; they lose less of it than standard varieties under the same dry conditions.

Two routes are used. The first is conventional breeding, which crosses plants and selects the best performers across many dry and wet seasons, sometimes with the help of markers. The second is genetic modification, which adds a gene to the plant. Bioceres Crop Solutions' HB4 trait, which is genetically modified, is an example of the second route. Companies report field results from it, but independent published yield data are still limited.

Technical explanation

Maize breeding for drought tolerance mainly aims to keep grain yield high under water stress rather than to make the plant survive. In southern Africa, Tarekegne and colleagues (2024) tested early maturing hybrids developed by the International Maize and Wheat Improvement Center in managed drought trials, where irrigation was withheld. In those trials, the tested hybrids averaged 41% higher grain yield than the commercial checks (range 21 to 70%). Under random, mixed stresses, the average advantage was 40% (range 17 to 62%). The authors describe the managed drought treatments as targeting 30 to 40% of the average yield under optimum management at the same location, which means the results describe severe stress, not typical seasons. The study reports a mean yield reduction of 67% under managed drought compared with optimum conditions.

Farm-level evidence is thinner and more mixed. A household survey of 200 maize growers in two districts of south-eastern Zimbabwe, published by Lunduka and colleagues (2017), found that growers of drought-tolerant varieties in the 2013/14 season averaged 680.5 kg per hectare, against 436.5 kg per hectare for growers of other varieties. The authors used a control function to address the fact that farmers choose which varieties to plant. Drought was not measured directly; the authors used households' reports of drought in the previous five years as a proxy. The comparison was with all other varieties, not with the best commercial hybrids.

Genetically modified HB4 crops follow a separate and slower track. HB4 soybean received a USDA approval in August 2019 according to its developer, and HB4 wheat was approved by Argentina's Ministry of Agriculture in October 2020. Both approvals rest on the company's own announcements. The company says HB4 wheat increased yields by 20% on average in field trials over the last ten years in drought-affected seasons, but the number of trials is not stated in the release.

What the evidence says

Each statement is typed by the strength of its evidence and linked to the source that supports it.

Demonstrated Shown in a published experiment, test or shipping product.

In managed drought trials, early maturing maize hybrids developed by CIMMYT in southern Africa yielded on average 41% more than commercial checks (range 21 to 70%); under random stress, the average advantage was 40% (range 17 to 62%).

Sources: [1] · Results and summary tables · medium confidence

The managed drought trials were designed to reach about 30 to 40% of average grain yield under optimum management at the same location, and under managed drought the mean yield reduction against optimum conditions was 67% (range 64 to 70%).

Sources: [1] · Methods and summary table

In a 2013/14 household survey of 200 maize growers in Chiredzi and Chipinge, Zimbabwe, growers of drought-tolerant varieties averaged 680.5 kg per hectare, compared with 436.5 kg per hectare for growers of other varieties; the authors call their results conservative.

Sources: [2] · Results · medium confidence

Tarekegne and colleagues note that absolute gains in farmers' fields could be lower than on-station yield levels.

Sources: [1] · Conclusions

Reported, unverified Stated by a company or team but not independently confirmed.

Bioceres reports that HB4 wheat increased yields by 20% on average in field trials over the last 10 years in drought-affected seasons; the release does not give the number of trials.

Sources: [3] · Release text · low confidence

Argentina's Ministry of Agriculture approved the HB4 wheat event for cultivation and consumption on 8 October 2020, according to Bioceres.

Sources: [3] · Release text · medium confidence

Bioceres announced on 28 August 2024 that USDA's Animal and Plant Health Inspection Service had concluded HB4 wheat does not pose an increased plant pest risk relative to comparator wheat, so it is not subject to the 7 CFR part 340 rules for genetically engineered organisms.

Sources: [5] · Release text · medium confidence

In August 2024, Pacific Northwest wheat commissions said it was unlikely that HB4 wheat would be commercially grown or available in the United States for at least three to five years, and that no genetically modified wheat was then grown commercially there.

Sources: [6] · Statement text · medium confidence

Verdeca announced USDA approval of HB4 drought-tolerant soybeans on 8 August 2019 and said the HB4 trait then held regulatory approval in more than 80% of the global soybean market.

Sources: [4] · Release text · medium confidence

Limitations and open problems

  • Most of the peer-reviewed yield gains come from managed drought trials at research stations, and Tarekegne and colleagues (2024) note that absolute gains on farms could be lower than on-station yield levels.
  • The farm survey by Lunduka and colleagues (2017) is a single cross-sectional study in two districts. The authors say that controlling for unobserved household and plot heterogeneity would need panel data, so differences between growers that the survey does not measure remain possible.
  • The HB4 wheat yield figure of 20% is a company claim, reported without the number of trials or the drought conditions.
  • Regulatory approval does not mean the crop is on sale. In August 2024, Pacific Northwest wheat commissions said HB4 wheat was unlikely to be commercially grown in the United States for at least three to five years, and that no genetically modified wheat was then grown commercially there.
  • Export markets can block commercial launch: the HB4 wheat launch in Argentina depends on import approval in Brazil, and HB4 soybean needed Chinese import approval for launch in Argentina.

Possible future uses

Speculative

Ideas, not predictions. None of these has been demonstrated.

  • Breeding programmes that combine HB4-type traits with conventionally bred drought tolerance in maize or soybean.
  • Drought-tolerant wheat grown in regions where the trait is approved and trade partners accept the crop.
  • Use of drought tolerance in insurance or crop-planning programmes where farmers can show a yield advantage over standard varieties.

Timeline

  1. 2017Lunduka and colleagues publish a household survey in Zimbabwe reporting higher average maize yields for growers of drought-tolerant varieties (680.5 kg per hectare compared with 436.5 kg per hectare). Sources: [2]
  2. 8 Aug 2019Verdeca (a joint venture of Arcadia Biosciences and Bioceres) announces USDA approval of HB4 drought-tolerant soybeans. Sources: [4]
  3. 8 Oct 2020Bioceres announces that Argentina's Ministry of Agriculture has approved the HB4 wheat event for cultivation and consumption. Sources: [3]
  4. 16 Jan 2024Tarekegne and colleagues publish genetic gain results for CIMMYT early-maturing maize hybrids in southern Africa, including yield advantages under managed drought and random stress. Sources: [1]
  5. 28 Aug 2024Bioceres announces that APHIS has concluded HB4 wheat does not pose an increased plant pest risk relative to comparator wheat, so it is not subject to 7 CFR part 340 rules for genetically engineered organisms. Sources: [5]

Futures this could help bring about

AI illustration
How far away?

Crops that keep yielding in drought

Scaling up · 3 of 7 steps done

Related breakthroughs

Glossary

Managed drought
A field trial design where irrigation is withheld, so the crop experiences a controlled water shortage.
Random stress
A field trial design where the crop faces several uncontrolled stresses mixed together over a season.
Commercial check
A widely grown commercial variety used as a benchmark when testing new varieties.
Genetic gain
The increase in yield that breeding adds each year, usually measured in kilograms per hectare per year.

Sources

  1. peer reviewed paper
    Genetic gains in early maturing maize hybrids developed by the International Maize and Wheat Improvement Center in Southern Africa during 2000-2018
    Amsal Tarekegne, Dagne Wegary, Jill E. Cairns et al.. Frontiers in Plant Science, 16 Jan 2024. DOI: 10.3389/fpls.2023.1321308. Accessed 22 Oct 2026.
  2. peer reviewed paper
    Impact of adoption of drought-tolerant maize varieties on total maize production in south Eastern Zimbabwe
    Rodney Witman Lunduka, Kumbirai Ivyne Mateva, Cosmos Magorokosho et al.. Climate and Development, 2017. DOI: 10.1080/17565529.2017.1372269. Accessed 22 Oct 2026.
  3. company announcement
    Bioceres Crop Solutions Corp. Announces Regulatory Approval of Drought Tolerant HB4 Wheat in Argentina
    Bioceres Crop Solutions (investor relations), 8 Oct 2020. Accessed 22 Oct 2026.
  4. company announcement
    Verdeca Receives USDA Approval of HB4 Drought Tolerant Soybeans
    Arcadia Biosciences, 8 Aug 2019. Accessed 22 Oct 2026.
  5. company announcement
    Bioceres Crop Solutions Receives Green Light for Cultivation of Drought Tolerant HB4 Wheat in the United States
    Bioceres Crop Solutions (investor relations), 28 Aug 2024. Accessed 22 Oct 2026.
  6. other
    Statement on genetically modified wheat trait
    Idaho, Oregon and Washington wheat commissions, 27 Aug 2024. Accessed 22 Oct 2026.

Revision history

3 changes since this profile was created.

Changes on 22 Oct 2026
Published on owner instruction (owner requested space, food and water topics)dc4cd89
Sources and claims re-checked against originals409337d
Initial profile drafted from primary sourceseaac9eb