Minor gene tactic for oat rust

Minor genes prove useful in protecting against rust in oats


Diseases
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Research shows minor genes remain useful in protecting against rust diseases in oats.

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Crown rust attacks the leaves and leaf sheaths of oat plants and is orange in appearance. PHOTO GRDC

Crown rust attacks the leaves and leaf sheaths of oat plants and is orange in appearance. PHOTO GRDC

Research over the past 20 years on resistance to rust in wheat has clearly shown that while some sources of resistance have been rendered ineffective by ever-evolving rust pathogens, others have stood the test of time and proved to be durable.

These durable resistances tend to provide a lower 'minor' level of resistance compared with resistances that are more often non-durable ('major') resistances.

Nonetheless, the level of protection afforded by the minor genes, while lower, is still very useful in protecting against yield losses due to rust, and can be increased by combining two or more such genes.

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For example, the old wheat cultivar Cook, released in 1977, has three minor genes for resistance to stripe rust that continue to provide a high level of resistance against currently prevailing pathotypes of stripe rust.

In contrast to the durability of some rust resistances in wheat, resistance to crown rust has been notoriously non-durable.

Since the mid-1990s, no fewer than 16 grazing oat cultivars have been released with 'major' resistance to crown rust, only to succumb to the appearance of new pathotypes (strains) that rendered each susceptible.

New pathotype

The most recent of these was the detection of a new pathotype virulent for the variety Comet (PBR) in 2018.

Based on our experiences with resistance to rust in wheat, we began to look for resistance to crown rust in oats that fits the 'minor' resistance model.

So far, we have screened thousands of oats from around the world, both as seedlings in greenhouse tests and as adult plants in the field.

This work resulted in the identification of hundreds of oat lines that carry 'minor' crown rust resistance, which we believe has a much higher chance of being durable if deployed in Australian agriculture.

Initial studies of five of these crown rust resistant lines have shown a similar story to that in wheat, with the presence of multiple genes which, when combined, give a high level of rust resistance.

In very recent work, we have discovered four new minor genes and developed DNA markers for each, and have begun the process of introducing them into oat lines that are adapted to Australian growing conditions.

Once we have completed this process, the lines carrying the new genes and the new DNA markers developed will be provided to oat breeders, who will be able to use them to develop new high-yielding oat varieties with what we hope will be robust and durable crown rust resistance.

GRDC Research Codes: US00063, DAS00133

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