The effects of selected factors on measured ergot alkaloid content in Claviceps purpurea-infected hexaploid and durum wheat

Abstract

Four wheat genotypes, including the ergot-susceptible durum ‘AC Avonlea’ and hard red spring wheat ‘AC Cadillac’, as well as the resistant durum wheat line 9260B-173A and the hard red spring wheat line ‘Kenya Farmer’ wereinoculated with different Claviceps purpurea isolates. Honeydew and sclerotia were collected and analysed for 10 ergot alkaloids. Total concentrations of the 10 ergot alkaloids ranged from 16 µg/kg in honeydew to 1,798 mg/kg insclerotia. Ergonovine and ergosine were the predominant alkaloids in honeydew obtained from plants inoculated with various isolates, whereas ergocristine and ergocryptine were the main alkaloids observed in sclerotia. Bothhost plant and C. purpurea isolate were significant factors affecting total ergot alkaloid concentrations in sclerotia. Irrespective of host plant line, all mean total ergot alkaloid concentrations were higher in sclerotia produced from the EI-2 isolate (695-1,010 mg/kg), as compared to EI-4 (255-594 mg/kg). The mass of total ergot alkaloids was alsopositively correlated with the mass of individual sclerotia produced from these two C. purpurea isolates, with the slope of the regression higher for the EI-2 isolate. The total ergot alkaloid concentrations in sclerotia from various plants inoculated with the same C. purpurea isolate differed; however, the resistance of host plant line did notappear to be consistent with ergot alkaloid content in sclerotia. Concentrations of total ergot alkaloids were highestand lowest in sclerotia from the two lines that are both classified as ‘resistant’, suggesting that the mechanism ofresistance for these lines is not restriction on the production of ergot alkaloids in sclerotia.