Long coleoptiles key to boosting yields

Probing coleoptile length has positive frost risk management spin-off

Frost Management
A germinating wheat seedling. PHOTO GRDC

A germinating wheat seedling. PHOTO GRDC

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Water-seeking wheats under development to optimise use of deep soil moisture resources.

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Deeper moisture-seeking sowing depths of up to 12.5 centimetres and a more flexible sowing window give long-coleoptile wheats the potential to boost average yields across Australia.

John Rochecouste, GRDC Manager Agronomy, Soils and Farming Systems North says wheat plants with long coleoptiles (the pointed protective cover that encases the emerging shoot) can be sown much deeper than the current practice of about five centimetres.

In seasons with dry late summers and autumns, deeper sowing enables germination using stored subsoil moisture that is accumulated during fallow periods, he says.

Current varieties that require shallower sowing are increasingly unable to be sown early (March, April, early May) due to dry conditions and dry topsoil. For many areas, especially in NSW, 2017 and 2018 were typical of such years.

Dr Rochecouste says winter habit wheats also have a more flexible sowing window than fast-developing, spring-habit types which are currently the most common type grown in Australia.

In some regions, winter wheats with appropriate maturity can be sown from late February through to mid-May," he says.

In seasons with dry late summers, deeper sowing enables germination using stored subsoil moisture accumulated during fallow periods. - GRDC Manager Agronomy, Soils and Farming Systems North John Rochecouste

The research, through a GRDC Grains Industry Research Scholarship investment, was carried out by graduate Bonnie Flohr working with James Hunt (La Trobe University), John Kirkegaard (CSIRO), John Evans (Australian National University) and Julianne Lilley (CSIRO).

Dr Rochecouste says, further underlying premise of the study, there is a significant amount of research supporting that early sowing where possible - and with appropriate varieties generally leads to higher yields and can potentially help growers manage abiotic stresses, such as late-season frost and heat stress.

This is particularly so if crop rotations are sound and a high standard of fallow management is practised to conserve fallow moisture.

Dr Rochecouste says wheat with the combination of long coleoptile and winter habit has the potential to be sown into wet or dry topsoil across a wide sowing window.

This provides growers with a chance to maximise yields in most seasons. Coleoptile lengths of modern semi-dwarf wheat varieties are significantly shorter than those of older, tall wheats in which genes for shorter straw closely linked to shorter coleoptiles.

Other CSIRO research (by wheat geneticist Greg Rebetzke and colleagues) has identified alternative dwarfing genes that can reduce crop height without reducing coleoptile length and early growth, as well as genes that actively promote longer coleoptiles. Short but adapted wheats with long coleoptiles are the target.

Lines with longer coleoptile genes have been released to wheat breeders.

Australian Grain Technologies winter wheat breeder, Britt Kalmeier, has included them in her program.

Breeders such as Ms Kalmeier emphasise it is going to be a challenge to incorporate these into winter wheats while retaining all the other important traits such as quality, high yield, resistance to diseases and good agronomic type.

In the simulation study, winter wheats with long coleoptiles established on stored subsoil moisture from the previous rotation achieved, on average, a mean yield increase of 1200 kilograms per hectare, or 42 per cent relative to the baseline.

Especially critical is that the results show winter wheats with long coleoptiles widen the sowing window and reliability of early establishment.

These results should be verified in field experiments.

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