Relationship of AUDPC values of tan spot and Stagonospora glume blotch with grain infection in winter and spring wheat.

Field and laboratory experiments were performed at the Lithuanian Institute of Agriculture over the period 2003–2006. The tests involved three winter wheat cultivars (‘Aron’, ‘Hereward’ and ‘Tauras’) and three spring wheat cultivars (‘Hena’, ‘Munk’ and ‘Nandu’). Different disease levels (untreated control, leaf spot disease severity 0–1.0%, 1.1–5.0%, 5.1–10.0% and 10.1–25.0%) were initiated by using leaf spot disease – infested wheat straw and fungicide applications. Leaf and ear disease assessments were done during wheat growing season. Phaeosphaeria nodorum and Pyrenophora tritici-repentis infection levels on grain were estimated in the laboratory under controlled conditions. A correlation analysis was done between tan spot AUDPC (area under the disease progress curve) values and grain infection by P. tritici-repentis and between the severity of Stagonospora glume blotch and P. nodorum infection on grain. Tan spot AUDPC values, in most cases, either did not correlate or correlated poorly (from 0.26 to 0.41) with grain infection by P. tritici-repentis in winter and spring wheat. The correlation analysis of Stagonospora glume blotch and P. nodorum infection on grain showed no relationship between these two parameters.