Under a national yellow spot project led by the Department of Primary Industries and Regional Development, a large multi-parent advanced generation inter-cross (MAGIC) population of 1,503 wheat lines was developed from a complex cross involving different sources of yellow spot resistance. The four parents included Australian wheat varieties GBA Ruby, H45, King Rock and Magenta. This population provided a unique opportunity to maximise genetic recombination and generate potential parental stocks enriched for yellow spot resistance. The population was phenotyped at the seedling stage at various national sites and 135 lines with high levels of seedling resistance were identified. The population showed continuous distribution and transgressive segregation for disease severity with a few lines showing higher resistance than all parents. Correlations between assessments made at various national sites were moderate (r = 0.4 to 0.6). The population was genotyped by University of Adelaide and several QTL for seedling resistance were identified of which the ones on 4A, 5A, 5B, 7B and 4D were of significance (LOD>3) and accounted for 10 to 28% of variation.

The set of 135 lines with high levels of seedling resistance were tested at various growth stages and environments at South Perth with the aim to identify lines with broad-spectrum adult plant resistance. There were moderate correlations between assessments made in different environments (r = 0.5) and at different growth stages (r = 0.6). The lines showed continuous distribution and transgressive segregation for disease severity in all trials with a few lines showing higher levels of resistance than all parents. Of these, 11 lines showed very high levels of resistance (RMR) at various growth stages and environments. These lines are being delivered to various breeding companies and are crucial genetic stocks for breeding.