[en] Mutation breeding in groundnut was initiated with a view to develop improved cultures for increasing production in India, which contributes over 33 percent to the world groundnut production. More than 50 mutants were isolated-influencing almost all features of a groundnut plant. Cytological M₁ variants produced more mutants and in advanced generations. Some mutants showed interesting genetic behaviour, while others exhibited differential expression in different seasons leading to masking of mutant characters. In addition, mutants having economically useful characters, such as large kernel size and increased yielding potential were also isolated. Using these and other mutants new Trombay Groundnut (TG) varieties were developed which had large kernels suitable for export trade, improved oil content and increased yields. Among them TG-17 was unique for its extreme fastigiata character leading to flowering at all nodes and reduced number of vegetative branches. Demonstrations of TG-varieties for high yielding potential, on the fields of cultivators were successful. Because of increasing demand for the seed, a seed multiplication programme was initiated in 1974-1975 in collaboration with a private organisation. Starting with one ton seed more than 2000 tons of seed was produced till the end of 1977 and distributed for cultivation in the current year. (author)