Multiplines are the mixture of

Multiplines are the mixture of Isogenic 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.
Isogenic lines are defined as individuals that possess the same genotype irrespective of their homo- or heterozygous nature.