Sample variation and resource allocation for ergot alkaloid characterization in endophyte-infected tall fescue

Ergot alkaloid concentrations vary among genotypes of endophyte-infected (E+) tall fescue (Festuca arundinacea Schreb.). Because the ergot alkaloids are responsible for detrimental health disorders in grazing livestock, but the endophyte Neotyphodium coenophialum (Morgan-Jones and Gams) Glenn, Bacon and Hanlin is mutualistic, development of E+ tall fescue populations low in ergot alkaloid concentration may be a sustainable non-toxic solution for livestock producers, Current techniques for screening ergot alkaloids in tall fescue are labor and equipment intensive and time consuming, The objective of this research was to determine the number of replications and locations needed to detect specified differences among treatments varying in alkaloid concentration. Six E+ tall fescue genotypes were harvested twice at two held locations and one greenhouse location in 1 yr, and the number of replications and environments required to show specific treatment differences for alkaloid concentration calculated within harvest dates. Ergot alkaloid concentrations for the genotypes ranged from 488 mg kg(-1) to 2504 mg kg(-1) in the spring, and 219 mg kg(-1) to 986 mg kg(-1) in the summer. Genotypic variances were proportional to the mean; hence, data were subjected to a log(10) transformation. Treatments harvested twice with differences of 50% of the experimental mean were detectable (P = 0.05) in experiments containing two replications grown at four environments, or two replications grown at three environments and harvested once when nontransformed or transformed data were used, respectively. Use of transformed data will be necessary to keep the number of observations per experimental unit manageable.