- Eyespot is a stubble-borne fungal disease of cereals that can lead to 20 to 40 per cent yield loss in susceptible wheat varieties
- A new screening method to identify varieties with genetic resistance will be used to rate resistance in existing varieties and identify resistance in breeding lines
GRDC-invested research by the South Australian Research and Development Institute has been investigating the epidemiology of eyespot and suitable management options.
A new screening technique gives growers and breeders the ability to select cereal varieties with improved resistance to eyespot.
Eyespot is a stubble-borne fungal disease of cereals caused by Oculimacula yallundae, which occurs in areas with prolonged cool and damp conditions early in the growing season. Eye-like lesions weaken plant stems, often resulting in lodging, creating harvest difficulties and yield losses of 20 to 40 per cent in susceptible wheat varieties.
Paddocks with high levels of inoculum can be identified using a PREDICTA® B soil test and cereal crops in risky situations should be visually monitored for eyespot lesions.
Eyespot can be managed by either growing varieties that are less susceptible to the disease, using a fungicide prior to canopy closure or having a break from cereals to reduce inoculum levels in the soil. However, eyespot resistance in Australian varieties is limited, and it has been difficult to develop accurate resistance ratings.
Field-based resistance screening is not cost-effective as paddocks with high levels of eyespot inoculum must be found and then seasonal conditions have to be conducive to eyespot infection and development.
For this reason, the South Australian Research and Development Institute (SARDI) has spent several years developing screening techniques using ‘artificial inoculation’ to accelerate the development of eyespot-resistant germplasm with reduced potential for yield loss.
New screening process
This screening method was used for the first time in 2020 to screen 15 existing bread wheat varieties and 15 breeding lines for resistance to eyespot.
In 2019, eyespot-infected stems were collected from paddocks and in March 2020 sets of three stems were hot-glued together to form pinwheels and placed outdoors to encourage spore development.
Groups of 25 plants by four replicates were grown outdoors in pots for each variety or line being screened. When the plants were at the two-to-three-leaf stage, one pinwheel of infected stems was introduced as the eyespot inoculum source for each group.
Overhead irrigation was applied at early tillering to simulate rainfall, followed by overhead misting to maintain humidity levels and create ideal conditions for eyespot spores to develop.
The plants were removed and scored for eyespot damage on the stem base at mid-grain fill.
The screening results for two ‘check’ varieties – LRPB Trojan and Mace – were consistent with earlier ratings based on extensive field screening, giving researchers the confidence to allocate provisional eyespot resistance ratings to other bread wheat varieties (see Table 1).
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Of the 15 breeding lines, several showed improved resistance to eyespot when compared to LRPB Trojan and Mace.
Now that the success of this screening technique has been demonstrated, researchers are ready to offer eyespot screening to plant breeders and help to speed up delivery of varieties with improved eyespot resistance to growers.