Compensating damage effects of seed-borne Fusarium culmorum and Microdochium nivale in winter wheat by increased seeding rates

Summary

Fusarium culmorum and Microdochium nivale are considered important seed-borne diseases of wheat in Denmark. Their damage effects consist in reducing seed germination and plant emergence which leads to reduced plant density, panicle numbers/area and yield. The aim of this study is to find out whether and to what degree these damage effects can be compensated by increased seeding rates. A trial was therefore conducted in 2004 in which seed lots of three winter wheat varities (Ritmo, Bill and Boston) having various degrees of infection by F. culmorum and Microdochium nivale were sown at various seeding rates. Seed contamination of the two pathogens was determined by counting the number of discoloured roots in the seed batches (Doyer method). Plant emergence was determined by counting the number of plants/area at seedling stage. A general linear model based on a term for [variety x pathogen] and a term for [variety x pathogen x germinating seeds/m2 x fraction of healthy seeds] explained ca. 70% of the variation in plant emergence. All parameters in the model were highly significant (p £ 0,005) and the R2 values of the individual variety x pathogen combinations ranged from 0.47 (Boston x M. nivale) to 0.85 (Ritmo x F. culmorum). The parameters of the model indicate that Boston was most responsive to an increasing seeding rate and/or healthy seed fraction, followed by Ritmo and Bill. This suggests that recommendations regarding the compensation of damage effects of seed-borne F. spp. and M. nivale by increasing seeding rates should be variety-specific. Supplemental results are expected from detailed analyses of the yield data and from an ongoing field trial. Further work will also include the development and use of molecular diagnostic tools to distinguish between various Fusarium spp. and M. nivale on contaminated seeds.