Rice genetics the key to water efficient production

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Dr Jaquie Mitchell in a rice crop

With the support of AgriFutures Rice Program Australian rice researchers are on the cusp of implementing molecular markers to make it easier to select plant varieties with the ideal traits for producing rice with less water – known as an aerobic rice production system where water availability is high but non ponded.

This “transformative” research is also shaping-up to deliver yield gains in the paddock and water savings for growers.

Led by University of Queensland Senior Agronomy Lecturer Dr Jaquie Mitchell, the project focuses on developing the technology to identify genetic factors to assist Australia’s rice industry with breeding plants that thrive in lower-water production systems, and have the ability to withstand low temperature events.

The hope is, these plant varieties would produce similar rice yields than traditional flooded production systems but ultimately using less water.

And this innovative pre-breeding technology, is not too far away either, according to Dr Mitchell.

“We have identified two sets of markers that indicate cold tolerance and traits for successful aerobic rice production systems.”

These molecular markers will be available to help the Australian Rice Partnership (funded by AgriFutures Rice Program, SunRice and NSW Department of Primary Industries) make data driven decisions about their cross selections–a plant breeding method, where desirable traits from parent plants are crossed with each other by manually pollinating one plant with another.

One of the key breeding goals is to develop a rice plant with cold tolerance.

Cold tolerance is crucial in an aerobic rice production system because, unlike the traditional practice of flooding rice fields which submerges the plant panicle and helps to protect it, in an aerobic system this would be exposed to cold temperatures.

The key to developing a cold tolerant, aerobic adapted rice variety includes identifying the genotypes (a set of the plants genetic material or DNA) that not only survive, but thrive in these conditions, and incorporating these traits into Australian rice breeding programs.

More than meets the eye

To identify the genes that affect the outcome of specific traits for cold tolerance, Dr Mitchell and her team monitored plants in controlled temperature glasshouses which mimicked likely conditions in the Riverina.

Dr Mitchell said this practice developed a phenotyping system which enabled identification of cold tolerant varieties at both booting and flowering stage.

A phenotype includes observable characteristics of the plants.

Both genotype and phenotype experiments are needed to identify these genes and the molecular markers for plant breeders to use in order to breed varieties with these desirable traits.

“There is no one gene responsible for cold tolerance,” according to Dr Mitchell, rather there are a number of genes and together they have a significant impact.

Dr Jaquie Mitchell in a rice crop

Helping to reduce risk

After one of the coldest seasons in more than 20 years and significant yield penalties for some growers, Deniliquin NSW rice grower Andrew Crossley said managing cold tolerance was front of mind for many growers and cold tolerant varieties would benefit everyone in the industry.

“The 2021 season was particularly challenging for many growers. A variety with cold resistance, that’s marketable and uses less water – and copes with high temperatures too– would tick all the boxes for a grower,” he said.

AgriFutures Australia Senior Manager (Levied Industries) Lucinda Staley-McCrohon said this project is one example of how the rice industry is working together to develop solutions to benefit the entire supply chain.

“This has been a multidisciplinary approach, encompassing crop physiology, agronomy, plant breeding and molecular genetics,” she said.

“For the breeders, this means they are able to select plant genetics for aerobic situations with greater accuracy. And for the grower, they can grow these varieties using less water and with confidence knowing they are unlikely to experience yield penalties as a result of cold weather events.”

Field findings

Very early findings from small and controlled evaluations of the cold tolerant, aerobic adapted rice variety at The University of Queensland Gatton campus, indicated it was possible to achieve the yields of up to 1.5 tonnes/megalitre of water.

Dr Mitchell said these experiments were irrigated either via an overhead or drip system and used a total of 7 megalitres per hectare.

Ms Staley-McCrohon reinforced while these trials are promising it is still very early days and further field trials were required in the Riverina to replicate the production systems for the majority of Australian rice growers.

The next step for this research involves providing the molecular markers for the traits to the plant breeders to incorporate into the Australian Rice Partnership.

Dr Mitchell said these markers would enable breeders to select varieties for aerobic production systems “from their desk”, rather than planting thousands of genotypes and completing what’s described as a “glasshouse screening”. Ultimately fast-tracking the development of breeding lines and varieties.

Aerobic rice production system – the basics

  • Sometimes deceivingly referred to as ‘DryRice’ production.
  • A production system where rice is grown in well-drained, and non saturated soils.
  • Establishment is dry direct seeding.
  • Aerobic rice still allows practices of conservation agriculture as used in upland crops, such as mulching and minimum tillage.
  • Unlike rice grown in a permanent water system, irrigation water is scheduled to match the water requirements of the plant.

Aerobic rice production systems – fast facts

  • Aerobic rice production offers a completely different environment for the roots and plants than an anaerobic system.
  • Rice must still be watered in an aerobic system, but early and controlled trials demonstrated significant water savings without yield penalties.

To register for updates on this project and the AgriFutures Rice Program visit agrifutures.com.au/rice

Related articles: Meet PhD student Ricky Vinarao

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