[en] Seed size is key agronomic factor and has been utilised for improvement of pod yield and confectionary trait in groundnut. Seed size is a polygenic trait and little is known about the mechanism of groundnut seed size development. A large seed mutant, TG 89 with 54% greater seed size was identified through an electron beam mutagenesis of a popular groundnut variety,TG26. Present study was undertaken to identify genomic locations for large seed trait in groundnut. Large seed mutant TG 89 was hybridized with a normal seed genotype ICGV 15007. A F2 mapping population with 124 plants was utilized for phenotyping for seed size. About 1431 Transposable element markers (TE) and simple sequence repeat (SSR) markers were employed for genotyping of this population. The linkage mapping and QTL identification was carried out using QTL IciMapping ver 4.1. Out of 1431 molecular markers screened, 83 markers were found polymorphic between TG 89 and ICGV 15007. Bulk segregant analysis with these markers revealed that three markers (Ah1TC3A12, TE 333 and TE 278) had a putative association with the mutant large seed trait. In order to map the genomic regions associated with seed size, F2 mapping population was genotyped with 64 polymorphic TE and 19 SSR markers. These markers were mapped on to the 14 linkage groups covering map distance of 1053 cM. The QTL analysis revealed a major QTL for the mutant large seed trait between flanking markers AhTE333 and AhTE810 in Arahy.05 chromosome with 13% PVE for the seed size. This QTL was located within map interval of 4.7 cM that corresponds to 16.6 Mbp of genomic fragment which harbours an ortholog of BIG SEEDS 1 gene. Quantitative RT PCR revealed downregulation of this BIG SEEDS 1 gene in the mutant indicating probable loss of function mutation in this gene. Current study identified a major QTL on Arahy.05 chromosome and provided a valuable information for candidate gene identification for large seed trait in groundnut. (author)