Answer:
A particular genotype does not necessarily guarantee a particular phenotype. Understanding what factors can change this expression is quite complex.. What is what i believe that above statement meant.
Step-by-step explanation:
Error is the stochastic variation associated with a particular observation of the phenotype (and is managed by use of replication and and appropriate experimental design). The phenotype is the result not only of the average effect of the different alleles at a given locus across test units and across environments, but is impacted by the interaction between the different alleles and the environments (including genetic backgrounds) in which they are evaluated. Phenotype is not simply the sum of the genotype effect and the environment effect, as indicated in the mathematical formula that you provide.
Hope I Helped!!!