Surprise findings turn up the temperature on the study of vernalisation

New evidence has emerged about the agriculturally important process of vernalisation in a development that could help farmers deal with financially damaging weather fluctuations.

Vernalisation is the process by which plants require prolonged exposure to cold temperature before they transition from the vegetative state to flower. For decades it’s been a key focus of research into plant development and crop productivity.

But how vernalisation might work under variable temperatures in the field has been unclear, as have some of the underlying molecular controls of the process.

The research carried out by John Innes Centre scientists in collaboration with colleagues in Hungary and France shows that vernalisation is influenced by warm conditions as well as cold, and a much wider temperature range than previously thought.

Led by Dr. Laura Dixon, the study began as an exploration into how variance in ambient temperatures might influence flowering regulation in winter wheat. But it unexpectedly uncovered an “extreme vernalisation response”.

“We have shown that vernalisation responds to warmer conditions than those classically associated with vernalising,” she said.

Before this study, we thought vernalization only happened up to a maximum of about 12°C, but the true temperature is much higher. This information is immediately useful to breeders.

The researchers used a panel of 98 wheat cultivars and landraces and exposed them to temperatures ranging from 13 to 25°C in controlled environments.

Findings

Normally, once the vernalisation process completes, plant growth is accelerated under warm temperatures. But the team identified one cultivar, named Charger, which did not follow this standard response.

Gene expression analysis revealed that the wheat floral activator gene (VRN-A1) was responsible for this trait.

Further experiments showed that the expression of genes that delay flowering is reactivated in response to high temperatures (of up to 24 °C). This demonstrates that vernalisation is not only a consequence of how long the plant experiences continuous cold.

The team is now looking to provide diagnostic genetic markers which will allow breeders to track the distinct allele responsible for this warm-temperature vernalisation trait.

They also hope to use their new knowledge of warm weather interruption to reduce the length of vernalisation in the breeding cycle, so that new wheat lines can be generated more quickly.

Dr. Dixon added: “This study highlights that to understand the vernalisation response in agriculture we must dissect the process in the field and under variable conditions.

“The knowledge can be used to develop new wheat cultivars that are more robust to changing temperatures.”