Multiline varieties are mixture of

Multiline varieties are mixtures of several similar pure lines.
Multiline variety is a mixture of several pure lines of similar phenotype(height, seed colour flowering time, maturity time and various other agronomic characteristics) but has different genes for the character under consideration the disease resistance means these are isogenic lines.
Multiline varieties are mixtures of genetically related lines that have different genes for disease resistance and offer farmers a way to tame outbreaks of rust, thus stabilizing annual wheat yields.