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

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

Quantification of leaf stripe, Pyrenophora graminea, in barley seed by real-time PCR

In some years, large amounts of organic seed lots are discarded due to the presence of high levels of seed-borne diseases. In barley it is especially the presence of the fungal species Pyrenophora teres (barley net blotch) and P. graminea (barley leaf stripe), which causes rejection of seed lots. A real-time PCR method for detection and quantification of P. graminea has been developed

Molecular diagnostic methods can prevent unnecessary rejection of organic seed lots

In some years, large amounts of organic seed lots are discarded due to the presence of high levels of seed-borne diseases. In barley it is especially the presence of the fungal species Pyrenophora teres (barley net blotch) and P. graminea (barley leaf stripe), which causes rejection of seed lots. A real-time PCR method for detection and quantification of P. graminea has been developed

Nye diagnosemetoder til udsædsbårne sygdomme

Nye diagnosemetoder giver mulighed for at skelne udsædsbårne svampearter, som hidtil har været meget vanskelige eller umulige at adskille med konventionelle metoder

Udsædsbårne sygdomme i økologisk såsæd - betydning og skadetærskler

Det økologiske projekt ORGSEED har givet ny viden om skadetærsklerne for de vigtigste udsædsbårne sygdomme i korn og ærter. I projektets sidste del vil disse tærskelværdier blive vurderet med henblik på justering. Sammenholdt med nye metoder til bestemmelse af den faktiske forekomst af udsædsbårne sygdomme, vil det give en mere sikker karakterisering af den økologiske såsæd og hermed mindre unødig kassation