Resistance to yellow spot in wheat grown under accelerated growth conditions

Yellow spot, also known as tan spot (YS), is a serious fungal foliar disease of wheat worldwide. The introduction of resistance to YS in wheat cultivars offers the most durable, economic, and environmentally safe management strategy. Adult plant resistance (APR) is preferred over seedling resistance to control other diseases in wheat and has the potential to offer non-race specific resistance to YS. The search for APR currently relies on screening vast numbers of wheat genotypes in the field, where expression is affected by environmental factors. We report a rapid phenotyping method for APR to YS that combines use of constant light and controlled temperatures to achieve accelerated growth conditions (AGC). A panel comprising 20 spring wheat genotypes was evaluated in four separate experiments: (1) seedling stage under regular greenhouse conditions; (2) adult-plant (AP) stage under AGC; (3) integrated seedling and AP disease assessment; and (4) AP stage in the field. Phenotypes from all AP experiments conducted under controlled and field conditions correlated well (r = 0.71-0.84), but correlations between AP and seedling phenotypes were weaker (r = 0.30-0.62). Moderate to high levels of APR were displayed by some genotypes (e.g. CIMMYT line 'ZWW10-50') that were equivalent to levels attained by seedling resistant cultivar 'Leichhardt'. An integrated cycle requires only seven weeks to complete, and provides a useful tool for breeders and pathologists to efficiently phenotype APR to YS under controlled conditions.