Bacteria can activate heat tolerance in crops

Beneficial bacteria can promote heat tolerance in crops and could ultimately be the quickest route to achieving sustainable agriculture, according to a new study by KAUST scientists.

Severe heatwaves are becoming more frequent and increasingly damaging to agricultural crops. Some plants have natural heat tolerance, while others acquire heat tolerance through exposure to hot and dry conditions. The process of breeding heat-resistant plants, however, can be time consuming and expensive. 

Experts have been exploring the potential for using microbes to protect plants. The new research demonstrates that root-dwelling bacteria can help their host plants survive extreme conditions, including drought and heat.

“Beneficial bacteria could become one of the quickest, cheapest and greenest ways to help achieve sustainable agriculture,” said study co-author Kirti Shekhawat. “However, no long-term studies have proven they work in the real world, and we haven’t yet uncovered what’s happening on a molecular level.”

To investigate, the researchers tested the power of the beneficial bacteria SA187 that lives in the roots of tough, resilient desert shrubs. The team coated wheat seeds with the bacteria and then planted them in the lab, along with seeds that were left untreated. 

After six days, the crops were exposed to temperatures of 44 degrees Celsius, or 111 degrees Fahrenheit, for two hours. Any longer exposure would have killed all the plants, explained Shekhawat. 

The experts found that untreated wheat plants suffered leaf damage and stopped growing. Meanwhile, the treated wheat plants were left unharmed and continued to thrive, indicating that the bacteria promoted heat tolerance.  

“The bacteria enter the plant as soon as the seeds germinate, and they live happily in symbiosis for the plant’s entire life,” said Shekhawat.

The wheat was relocated and raised in natural fields in Dubai, where temperatures can reach 45 degrees Celsius. In this region, wheat is usually grown only in winter, but the crops treated with bacteria consistently produced yields between 20 and 50 percent higher than normal. 

“We were incredibly happy to see that a single bacterial species could protect crops like this,” said Shekhawat.

Genetic analysis revealed that the bacteria produce metabolites that are converted into the hormone ethylene, which primes the plant’s heat-resistance genes for action. “Essentially, the bacteria teach the plant how to use its own defense system.”

Thousands of other bacteria have the potential to protect plants against threats ranging from drought to fungi, and the team is already testing some of these microbes on vegetables and other crops. 

“We have just scratched the surface of this hidden world of soil that we once dismissed as dead matter,” said study lead author Heribert Hirt. “Beneficial bacteria could help transform an unsustainable agricultural system into a truly ecological one.”

The study is published in the journal EMBO Reports.

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By Chrissy Sexton, Earth.com Staff Writer