COGGO study aims to prevent bacterial ice nucleation when frost occurs

By Shannon Beattie
March 29 2022 - 10:00am
Two-year study to assess ice nucleation

PREVENTING bacterial induced ice nucleation to increase the productivity of grains is the aim of a two-year project by Murdoch University which recently received funding from the Council of Grain Grower Organisations (COGGO).

Frost damage occurs due to the formation of ice crystals that cause plant cell and tissue damage.

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It is estimated to cost Australian graingrowers about $400 million each year and even a small reduction in frost susceptibility (as little as 1°C) could save $148 per hectare in frost-prone areas of the WA grainbelt.

Murdoch University honorary research fellow Julie Ardley said one of the impacts of climate change was that despite increased global warming, the potential for crops to suffer frost damage may actually increase, due to changes in the plants' growth cycles.

"For cereal crops, this can mean that the frost-sensitive flowering stage (anthesis) occurs earlier, when there is still a danger of frosts," Dr Ardley said.

"Frost events during anthesis cause frost-induced sterility and result in greatly reduced yields."

Recent research by the Department of Primary Industries and Regional Development (DPIRD) has discovered the risk of frost damage is increased due to the presence of ice nucleation active (INA) bacteria on the leaves of crop plants and on stubble.

Ice crystallisation in plants typically requires temperatures below -8 to -10°C.

However, INA bacteria produce a protein that increases the freezing point of water, triggering the formation of ice crystals and causing frost damage to occur at temperatures four to five degrees warmer, about -2 to -5°C.

"Current efforts to reduce frost damage have focused on reducing the stubble load and on strategies such as zoning, variety maturity and sowing date to reduce the frost exposure," Dr Ardley said.

"However, as the INA bacteria (Pseudomonas syringae strains) are ubiquitous in aerosols and in clouds, these methods cannot prevent the INA bacteria from colonising grain crops."

Together, Murdoch and DPIRD are working on a COGGO-funded two year project that aims to reduce frost damage in cereal crops by preventing this colonisation.

One strategy is to develop non-ice-nucleation active (NINA) bacteria that can be applied as an inoculant to crops to compete with and reduce the concentrations of INA bacteria.

This has been successfully done in horticultural crops in the United States, using a Pseudomonas syringae strain that was genetically modified to remove the INA gene.

However, Dr Ardley said using a GMO presents issues with its release to the environment.

"Our approach will use the new CRISPR-Cas genome editing techniques to produce a non-GMO Pseudomonas syringae that lacks the INA gene and is suitable for field release," she said.

"We have isolated and identified several strains of Pseudomonas syringae INA bacteria from cereal crops that we will use to develop our NINA Pseudomonas syringae strain.

"Glasshouse and field trials will then establish the effectiveness of this strain in reducing INA bacteria numbers and subsequent frost damage in cereal crops."

Other strategies being investigated to prevent INA bacteria colonisation of cereal crops include developing natural compounds that can be sprayed on the crop to reduce the numbers of INA bacteria, or to inhibit the activity of INA proteins.

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