Vavilov wheat accessions provide useful sources of resistance to tan spot (syn. yellow spot) of wheat

Abstract

Host genetic resistance is the most effective and sustainable means of managing tan spot or yellow spot of wheat. The disease is becoming increasingly problematic due to the adoption of minimum tillage practices, evolution of effectormediated pathogenicity, and widespread cultivation of susceptible cultivars from a narrow genetic base. This highlights the importance of broadening the diversity of resistance factors in modern breeding germplasm. This study explored 300 genetically diverse wheat accessions, originally sourced from the N. I. Vavilov Institute of Plant Genetic Resources (VIR), St Petersburg, Russia. The collection was screened for resistance to tan spot at seedling and adult stage under controlled conditions, and in the field across 2 years. The phenotypic datasets, coupled with ToxA bioassay screening, identified a number of accessions with useful sources of resistance. Seedling disease response corresponded well with ToxA sensitivity (r = 0.49, P < 0.000), but not adult responses (r = 0.02 to 0.19, P < 0.002), and overall reactions to ToxA appeared to show poor correspondence with disease response at the adult stage. ToxA-insensitive accessions were generally found resistant across different growth stages (all-stage resistance, ASR) in all experiments (seedling and adult stage under controlled conditions and field). ToxA-sensitive accessions that were susceptible at seedling stage, but resistant at both adult-plant stages, were deemed to carry adult-plant resistance (APR). This study provides detailed information on the degree of tan spot resistance in the Vavilov wheat collection and discusses strategies to harness these sources to boost the diversity of resistance factors in modern wheat breeding germplasm.