Ensuring plant development is matched to optimum seasonal conditions is a key means to maximise crop performance. This is achieved through adjusting the timing of life cycle events of plants, known as phenology – a fundamental goal of cereal breeders.

As oats have a number of different end products – fodder, hay and grain – harvested at different times of the plant’s life cycle, optimising the development pattern for different varieties is challenging (Figure 1).

Genes that underlie this variation have been identified in wheat and barley, including those that modify the extents to which vernalisation (prolonged winter cold) or long daylengths are required to trigger flowering. Plant breeders have been using this knowledge for centuries to select for improved adaptation; however, modern scientific developments are now making this process more precise.

For example, gene-based models are being developed to predict when specific varieties will flower at different sites or

Figure 1: Schematic representation of the oat life cycle, including phase durations (vegetative, reproductive and ripening) and their impact on yield in a typical Australian context. sowing dates, which can inform crop management decisions.

Modified from Trevaskis B et al. (2022) Advancing understanding of oat phenology for crop adaptation. Front. Plant Sci. 13:955623. doi: 10.3389/fpls.2022.955623

Although it is known that oat is a vernalisation-responsive long-day plant that flowers after winter as days lengthen in spring, less is known about genetic control of oat development. An improved knowledge of the genes that regulate oat phenology has potential to drive rapid gains in breeding and to contribute to production of new crop management tools.

To this end, GRDC has invested with a team led by CSIRO in a project aiming to understand the genetic variation that influences the phenology of oats in Australian and international breeding programs.

Bringing together multidisciplinary skills, the team has experience in crop data science (CSIRO), agronomy (NSW Department of Primary Industries and Charles Sturt University) and molecular genetics (University of Adelaide), who have all worked extensively in aspects of wheat and barley phenology.

The team combines data-driven methods to understand crop biology, including the application of genomics and phenomics, together with the development of new analytical approaches and field and glasshouse observations to unravel plant adaptive responses. Of particular importance is resolving gene-environment interactions to understand and predict the flowering behaviour of oats at a range of locations.

Stocktake

Starting in July 2020, the team began by compiling a pedigree database of Australian oats breeding history by tracing the parentage of modern varieties. This pedigree database includes more than 1000 oats and extends back to the earliest modern varieties, circa 1892.

Using an overview of global breeding pedigrees, the team selected a panel of approximately 300 oat accessions to form a ‘core population’ for genetic analyses – the ‘OzOat population’.

This population includes Australian varieties as well as diverse international oats. The accessions have been chosen to capture genetic diversity but also a high degree of gene shuffling (recombination), which enables genetic analyses.

The OzOat panel has been grown in controlled glasshouse experiments to record when different accessions flower under different daylengths and to provide pure seeds for further genetic analysis. Preliminary phenology data demonstrated that the population captures a wide range of diversity in oat flowering behaviour.

A subset of about 80 lines has now been grown in field conditions at Wagga Wagga (NSW) to validate observations of flowering behaviour made in controlled conditions. The trial was sown at two dates (7 May and 2 June 2021) and the timing of different developmental stages – such as panicle emergence, anthesis and plant maturity – were recorded, as well as some other traits, such as plant height, panicle architecture and yield components.

Data has confirmed that the OzOat panel captures a wide range of flowering behaviours and is more diverse than modern Australian oats. This provides a good starting point to breed new Australian oats with flowering behaviours suited to emerging farming-system needs, such as earlier sowing. This will be further evaluated with another field season in 2022.

Genetic interrogation

Oats are a member of the Avena genus that is part of the same subfamily of grasses as wheat and barley. This close evolutionary relationship, combined with the similar flowering physiology of wheat, barley and oats, suggests there are good prospects to transfer knowledge from wheat and barley to oats. This could be the case for genes that code for both vernalisation and photoperiod responses.

To understand the genetic basis of plant development, in parallel to the phenology studies, the OzOat population has been genotyped using a genotyping-by-sequencing protocol optimised for oats. Essentially, this allows the team to read differences in the oat genetic code, across the entire genome.

Using statistical methods and machine learning, the team will link variation in flowering behaviour that may be driven by vernalisation or photoperiod responses to specific changes in the genetic code. This knowledge could then be used by oat breeders to select lines that have desirable flowering behaviours using DNA diagnostic technologies (for example, molecular marker platforms) that will accelerate the plant breeding process.

Yield components

Not only do phenology genes play a central role in adaptation, but also they are likely to influence developmental traits that underlie grain yield, as is the case for other temperate cereals. It is therefore a logical step with this adaptation work to start to dissect the genetic driver of yield components for oats.

The grain-producing flowers of oats are arranged on an inflorescence known as a panicle. Spikelets develop on elongated branches that radiate from nodes on the main stem and on secondary branches. This contrasts with the compound inflorescences of wheat and barley, where spikelets are attached directly to the main inflorescence stem. Panicle length and the number of branch nodes produced on each panicle can vary, both with genotype and environment (Figure 1).

Historically, oat yield improvements have been slow in comparison with other crops, due partly to proportionally less investments owing to the volume of the oats produced. However, once the genetic basis of the adaptive traits for oats are understood and this knowledge is combined with the latest genomic technologies, the team will be able to make large gains by manipulating oat development to increase the components of yield.

More information: Dr Ben Trevaskis, ben.trevaskis@csiro.au

Read more: Advancing understanding of oat phenology for crop adaptation.