Genetic variation of winter rye cultivars for their ergot (Claviceps purpurea) reaction tested in a field design with minized interplot interference

Ergot caused by Claviceps purpurea (Fr.) Tul. is a serious threat to rye(Secale cereale L.) cultivation. It produces sclerotia containing amixture of alkaloids toxic to animals and humans. For improvingergot resistance in rye a reliable field testing with a minimaldisturbance by pollen transfer between plots is indispensable. Weevaluated 85 rye cultivars of four types of cultivar (population,synthetic, and hybrid cultivars, hybrids blended with 10% populationrye) under inoculation in 3 years (2005, 2006 and 2007) and analysedergot incidence (% of affected heads) and ergot severity (% of sclerotiain grain by weight) at nine and ten environments (location • yearcombinations), respectively. Cultivar types were separated by borderplots and each entry was additionally surrounded by four border plotsof similar size (3–8 m2) in a chess-board design. Disease level rangedfrom 10–27% affected heads and 0.7–2.6% sclerotia in grain inindividual environments. Both, cultivar type and cultivars showedsignificant (P = 0.01) variation for both traits, interactions withenvironment were also significant (P = 0.01). Population cultivarshad less than half the disease level than the other types of cultivar forboth traits. Synthetic, hybrid, and blended hybrid cultivars did onaverage not differ significantly from each other. Blending had anergot-reducing effect only for the more susceptible entries. The besttwo hybrid cultivars showed an ergot reaction similar to somepopulation cultivars. However, the best population cultivar still hadonly half the amount of sclerotia in grain than the best hybrid cultivar(0.37% vs. 0.89%). Ergot incidence and ergot severity were highly(P = 0.01) correlated. We conclude that a good genotypic differentiationamong rye cultivars is achievable by field inoculation ofClaviceps purpurea across years with this design and testing withinnational listing trials is feasible.