Epidemiology of Septoria tritici and S. Nodorum: VII. Effects of the previous year's infection on disease development and yield in spring wheats

Abstract

Three spring wheat varieties, Opal, Kolibri and Sterling, were inoculated with Septoria tritici Rob. and S. nodorum Berk. at different growth stages in 1970, producing variable levels of head infection at harvest. Assessment of seed infection showed that S. nodorum levels were highest on seed from plants that had been inoculated at the early heading stages. No S. tritici was isolated from the seed. A sample of seed from each plot was sown in spring 1971. Percentage seed germination was not affected significantly by the time of inoculation with either fungus in 1970, but S. nodorum inoculation in 1970 reduced germination slightly in Kolibri and Sterling and stimulated it slightly in Opal. No S. tritici and very little S. nodorum were found on the plants in 1971. Yield parameters were unaffected by the inoculations of the previous year, although there were significant effects of both fungi on fertile tiller number in 1971. Very low levels of S. nodorum were found on the seed harvested in 1971.