The effect of environmental factors and plant genotype on the severity of Claviceps purpurea in winter rye

Claviceps purpurea causes ergot, a serious disease of rye and grasses. Resistance genes to the pathogen have not been found in the genome of rye so far. Therefore we evaluated 90 rye genotypes in two seasons at three locations and analyzed the ergot incidence. In one location (Smolice) the same genotypes were also used to assess the influence of water spraying during rye flowering on ergot occurrence. Moreover, 29 cytoplasmic male-sterile genotypes of rye were used in Poznan, where within a 5 km distance there were no rye plants. In the first two experiments the source of the pathogen consisted of its sclerotia introduced into the soil, whereas in the third experiment a suspension of conidiospores was used to spray the plants from the moment of first flowering. Percentage of sclerotia in grain by weight in the first two experiments and sclerotia weight per ear in the third experiment were used as a measure of rye susceptibility to C. purpurea. Both rye genotype and location (weather conditions) showed significant variation for both traits. Low temperature and rainfall during rye flowering increased the occurrence of ergot. Water spraying of rye during flowering also boosted the occurrence of ergot. In another experiment, with sclerotia of C. purpurea used as inocula, ergot occurrence varied from 0 to 4.73 % in 2011/12 and from 0 to 5.22 % of sclerotia in grain yield in 2012/13. Cytoplasmic male-sterile rye inoculation with conidia of C. purpurea resulted in sclerotia presence which ranged from 0.10 to 0.26 g per ear.