请教下面一段话的具体含义：

 genotype and field data from multiple environments was conducted using the procedure GLM from the SAS software (SAS Institute 1999). In each environment, the field data of all replications were averaged by the least square means option in SAS. The model used to detect QTLs included the effects marker genotype (M), environment (E) and M  E interaction. Under the assumption of a mixed model with the marker as a fixed effect and the environment as a random effect, the mean square of M  E was used as the error term for the computation of the Fstatistic for a marker main effect. The mean square of the residual variance was used as the error term for the computation of the Fstatistic for a M  E effect.

这里的the least square means 如何计算? fixed effect 和random effect 具体含义是什么？如果用GLM运行此程序的话，该如何编写？

请各位高手帮忙

[此贴子已经被作者于2008-12-16 9:53:11编辑过]