Relationship between wheat seed infection by Stagonospora nodorum and seed weight.
The relationship between wheat seed infection by S. nodorum [Phaeosphaeria nodorum] and seed weight was investigated in Lima, Waterloo, Snyder, Ketola, New York, USA, during 1995 and 1996. Seeds of winter wheat cultivars grown in eight production environments over two years were assayed for S. nodorum. The effect of seed infection by S. nodorum on 1000-seed weight, after accounting for the effects of production environment, cultivar, environment by cultivar interactions, and seed infection incidence by Fusarium species, was investigated by multiple linear regression. Regression models accounted for 94% of the variation in 1000-seed weight. Seed infection by S. nodorum was not significantly associated with any of the variation in 1000-seed weight in the year with relatively low disease incidence, but was significantly associated with reductions in 1000-seed weight in the year with high disease incidence (P≤0.0001). An increase in seed infection incidence of 10%, however, reduced 1000-seed weight less than 1 g. Seed infection incidence by S. nodorum is therefore not a major factor in reducing wheat seed size. Even lots consisting mostly of large seeds may be highly infected by S. nodorum.