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

Abstract

With 2 figures and 5 tables Abstract Ergot caused by Claviceps purpurea (Fr.) Tul. is a serious threat to rye (Secale cereale L.) cultivation. It produces sclerotia containing a mixture of alkaloids toxic to animals and humans. For improving ergot resistance in rye a reliable field testing with a minimal disturbance by pollen transfer between plots is indispensable. We evaluated 85 rye cultivars of four types of cultivar (population, synthetic, and hybrid cultivars, hybrids blended with 10% population rye) under inoculation in 3 years (2005, 2006 and 2007) and analysed ergot incidence (% of affected heads) and ergot severity (% of sclerotia in grain by weight) at nine and ten environments (location × year combinations), respectively. Cultivar types were separated by border plots and each entry was additionally surrounded by four border plots of similar size (3–8 m2) in a chess-board design. Disease level ranged from 10–27% affected heads and 0.7–2.6% sclerotia in grain in individual environments. Both, cultivar type and cultivars showed significant (P = 0.01) variation for both traits, interactions with environment were also significant (P = 0.01). Population cultivars had less than half the disease level than the other types of cultivar for both traits. Synthetic, hybrid, and blended hybrid cultivars did on average not differ significantly from each other. Blending had an ergot-reducing effect only for the more susceptible entries. The best two hybrid cultivars showed an ergot reaction similar to some population cultivars. However, the best population cultivar still had only 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 differentiation among rye cultivars is achievable by field inoculation of Claviceps purpurea across years with this design and testing within national listing trials is feasible.