Remember APR when selecting varieties
Author: Rachel Bowman | Date: 21 Dec 2012
Northern region grain growers are being reminded to consider adult plant resistance (APR) to fungal diseases such as stem, stripe and leaf rust, when retaining seed this harvest for next year’s crop.
Varieties carrying APR genes are protected from rust during the post-seedling stage of crop development, typically between tillering and booting (growth stages 20-49).
However, Professor Robert Park, from the Australian Cereal Rust Control Program, said because the timing and effectiveness of APR varies from gene to gene, it varies from variety to variety depending upon which gene(s) are present. It can also be temperature-sensitive, with expression delayed by cool weather.
“Variety choice is the first place to start when planning a cropping management program and APR should be one of the factors taken into consideration,” Prof. Park said.
“The presence of APR to rust can complement a fungicide strategy by protecting those parts of the plant most responsible for yield.”
A new fact sheet from the Grains Research and Development Corporation (GRDC) will assist growers in understanding how the APR trait works, why it is important in varietal selection, and how this knowledge can make fungicide application decisions easier.
The GRDC fact sheet contains wheat varietal ratings for APR to stem, stripe and leaf rust, and growers are encouraged to select varieties that are rated with at least the minimum disease resistance standard (MRMS) in the northern region, and in high-risk regions varieties rated MR or better are recommended.
Prof. Park said only growers with the resources, experience and time available to manage a potential rust outbreak should consider the risk of choosing a high-yielding variety that is moderately susceptible (MS) or susceptible (S) to rust.
“In a mixed farming situation, where other enterprises require attention there may not be time to monitor crops closely. In this case, a resistant (R) or moderately resistant (MR) variety or a pre-planned fungicide strategy is recommended,” he said.
“Very susceptible (VS) varieties should be avoided. They result in significantly increased spore production even compared to susceptible (S) varieties. This greatly increases the risk of damaging epidemics.
“Where more susceptible varieties are used, ensure a suitable fungicide strategy is in place and the right chemicals are available at short notice.”
Prof. Park said farmers should also consider seedling resistance ratings when selecting varieties – in some varieties the genes providing protection at the seedling stage provide complete resistance at all growth stages.
“If a particular variety only has APR, it may be susceptible in early growth stages (prior to GS20),” he said.
GRDC Northern Panel Chair James Clark said that foliar fungicides could be effective in controlling rust outbreaks, but all current fungicides generally were only intended to stop new infections rather than cure existing infections.
“Fungicide applications on badly infected crops provide poorer control than APR and do not restore lost green leaf area,” Mr Clark said.
“If a variety is vulnerable at the seedling stage, at-sowing fungicide treatments can be a cost-effective defence against rust. If a variety is vulnerable right through the season, then chemical control at seeding will provide initial protection but a further in-crop foliar fungicide application may be required.”
The GRDC Adult Plant Resistance Fact Sheet was distributed to growers in the latest edition of GRDC’s Ground Cover publication and is available for free download at www.grdc.com.au/GRDC-FS-AdultPlantResistance
PHOTO CAPTION: Northern region grain growers are being reminded to consider adult plant resistance (APR) to fungal diseases such as stem, stripe and leaf rust, when retaining seed this harvest for next year’s crop.
Media releases and other media products can be found at www.grdc.com.au/media
For interviews contact:
James Clark, GRDC Northern Panel Chair
0427 545 212
Professor Robert Park, Australian Cereal Rust Control Program
02 9351 8806
Rachel Bowman, Cox Inall Communications
07 3846 4380 / 0412 290 673
GRDC Project Code US00039