Ergot and ergot alkaloids in French cereals: occurrence, pattern and agronomic practices for managing the risk

Abstract

Ergot is a disease of cereals and grasses caused by the ascomycete fungus Claviceps purpurea (Fr.) Tul. This fungus infects young, usually unfertilised ovaries, replacing the seeds with dark mycelial masses known as sclerotia. The amount of sclerotia in marketable grain is strictly regulated in many countries. We found that ergot and its alkaloids were common in French farm fields during the 2012, 2013 and 2014 harvests. Before cleaning, ergot was present in harvest samples from 23 to 30% of wheat fields, 15 to 30% of durum wheat fields, 27 to 39% of barley fields, 45 to 66% of triticale fields, 12 to 29% of oat fields and 67 to 81% of rye fields. Triticale and rye were thus the cereals most prone to infection. The proportion of total ergot alkaloid in sclerotia varied, but the relationship between ergot sclerotium content and total ergot alkaloid concentration in the grain was strongly positive and independent of harvest year and cereal species. Ergot sclerotia content explained 75% of the variance for alkaloid content. We found that the main alkaloid and corresponding epimer, per gram of sclerotia, were ergotamine (29.2% of total ergot alkaloids), followed by ergosine (26.3%), ergocristine (18.5%), ergometrine (9.8%), ergocryptine (8.2%) and ergocornine (7.9%). The -ine isomers accounted for 70.5%, with the -inine isomers accounting for the remaining 29.5%. The mean total alkaloid content of C. purpurea sclerotia was 3,103 µg/g. This survey identified and ranked agronomic practices for limiting the risk of ergot contamination in crops. Host plant, previous crop, grassweed presence and tillage system all had a significant influence on alkaloid content. We identified and ranked agronomic practices for limiting and managing the risks of ergot and ergot alkaloids in the field. However, the main factor driving ergot infection is weather conditions.