Grain yield is closely associated with kernel weight. Cell wall invertase (CWI) and sucrose synthase (SUS) are one of the most important enzymes for sink tissue development and carbon partition, and has a high association with kernel weight. Allellic composition of the TaCwi-A1 and TaSus2-2В loci was tested in 79 winter wheat cultivars using a co-dominant markers CWI21- CWI22, which amplified 404 or 402-bp and Sus2-185/589H2- Sus2-227/589L2, which amplified 423 or 381-bp fragments in different wheat accessions respectively. Some samples carried the mutation in the TaCwi-A1 locus that negatively affects thousand-kernel weight (TKW) were shown to have TKW higher than the cultivars and lines that do not have this mutation in their genomes and despite the significant differences in TKW (from 39,4 to 59,8 g), all investigated varieties possess Hap- L haplotype. It can be attributed to the fact that the TaCwi-A1 and TaSus2-2В are only two of the genes associated with kernel weight and its allelic composition analysis cannot explain all phenotypic variances.