Email: karanjeet.sandhu@sydney.edu.au , robert.park@sydney.edu.au

Bread wheat provides an important source of food and nutrition, and it’s cultivation covers more than 218 million hectares worldwide. Demand of wheat is on the rise and to meet this requirement wheat production must increase, whereas rust diseases continue to be an ongoing significant constraint to wheat production.

Epidemics of rust diseases can cause major yield losses worlwide. Rust diseases can be managed using adult plant resistance (APR) as APR genes are considered durable, for example Yr18/Lr34/Sr57, Yr29/Lr46/Sr58 and Sr2 have been commonly used across the wheat breeding programs. Expression of APR can be dependent on a number of factors like genotype, growth stage and climatic conditions. The knowledge of expression of APR is crucial for making selections and breeding for rust resistance to achieve the integrated management of rust diseases.

Phenotyping for APR using multiple pathotypes is not practical under field conditions, and only one cycle of APR screening can be achieved during crop season. Comparative experiments conducted in the greenhouse (GH) vs LED growth rooms indicated the early expression of APR to wheat stripe/yellow rust (WYR) in LED growth rooms. Different genotypes carrying seedling resistance or APR for WYR, or leaf rust (WLR), or stem rust (WSR) were grown under 240W LumiLED lights, at an average temperature of 23 and Day/Night cycle: 20hrs light / 4hrs dark.

Plant growth was much faster under LED lights as compared to the plants grown in the GH under natural Day/Night cycle. Replications of plants grown in LED growth room for one week, and for six weeks were inoculated on same day using different pathotypes of WYR, WLR, and WSR causing pathogens. Post incubation, plants were moved to LED growth rooms set for Day/Night cycle: 13hrs light / 11hrs dark, for WYR development at 19 (average 2for both WLR and WSR development at 23 (average 23expected expressions of seedling resistance and APR were recorded after 12–14 days of inoculation, and cycle of APR phenotyping was completed in less than eight weeks.

Additionally, near isogenic lines with known genes for APR to WYR were grown in GH for 10 weeks and Flag-1 leaves were point inoculated to quantify the expression of APR. Cycle of APR quantification under GH conditions was completed in 12 weeks. Results from the point inoculations of multi-pathotypes indicated pathotype specific response of APR to WYR.

Developed methodology can allow the phenotyping of APR throughout the year by eliminating the wait for crop season, however, we suggest the validation of selections under field conditions. These novel methods of high-throughput & cost-effective multi-pathotype phenotyping for APR in LED growth rooms, allowing 5–6 cycles per year can fast track the breeding of wheat cultivars with durable rust resistance.