Blé <- read.table("https://husson.github.io/livre_exo/chap11_ex4.csv", header = TRUE, sep=";", encoding = "latin1", stringsAsFactors = TRUE)

Blé[,"Dose"] <- as.factor(Blé[,"Dose"])

summary(aov(Rendement ~ Variété + Dose + Variété:Dose,data=Blé))