Searching for adaptive traits; like finding a needle in a haystack?

Plant breeders are always looking for new genotypes with valuable traits, such as drought, salinity and disease resistance. But they often have a problem locating suitable material. The world’s genebanks contain about 7.2 million accessions, or seed samples. So if a breeder wants genotypes with a particular trait, where does he start? It is like looking for a needle in a haystack.

This is where the Focused Identification of Germplasm Strategy (FIGS) has a role to play. This new approach, which was developed by the International Center for Agricultural Research in the Dry Areas ICARDA in collaboration with an Australian–Russian team, gives researchers the ability to more easily locate specific traits in large germplasm collections.

Finding those elusive traits

Plants survive in harsh, hostile environments by developing adaptive traits that allow them to overcome environmental stresses. So to find genotypes with a specific trait, researchers need to first find environments where that particular trait is needed. This is the rationale behind FIGS.

FIGS creates ‘best-bet’ trait-specific subsets of material by passing accession-level information through a series of filters that increase the chances of finding the adaptive trait of interest.

Sunn pest resistance

The ICARDA genebank holds more than 133,000 accessions, including around 33,500 accessions of wheat and related species. FIGS was set to work in the genebank to find sources of resistance to Sunn pest (Eurygaster integriceps), the major pest of wheat in West and Central Asia and eastern Europe. FIGS identified 534 likely accessions. Initial field screening then reduced these to 57, and advanced screening resulted in nine entries with resistance to Sunn pest at the vegetative stage. They are now being used in ICARDA’s wheat breeding programs to develop wheat varieties resistant to Sunn pest feeding at the vegetative stage.

Recent FIGS successes

Powdery mildew resistance: A FIGS best-bet set of 1320 wheat accessions was supplied to Zurich University for powdery mildew screening. They found 211 accessions that were resistant to at least one of the four mildew isolates used in the screening. Later studies identified 15 new sequences and at least two new functional genes.

Resistance to Russian wheat aphid: In screening sets of 500 accessions for resistance to the Syrian Russian wheat aphid biotype (the most virulent version known), FIGS led to the identification of 12 resistant accessions. Subsequent analysis showed that a new source of resistance had been discovered.

Salinity tolerance: The FIGS approach was also used with a core set of bread wheats to identify a best-bet subset of 320 accessions for salinity tolerance. These accessions were exposed to salty water for 10 days, after which the sodium content of the leaves was measured. Researchers found that 21% had a desirable level of sodium. Yet only 3% of the accessions in the core set had such low levels – which shows just how effective FIGS can be in finding material that can overcome abiotic constraints.

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Photo credit: ICARDA