[en] Full text: The large scale cultivation of soybean in India (nearly 2 million ha at present) with yellow seeded varieties is a comparatively recent development. In early times, black seeded soybean was grown on a limited area, under local names like ''Bhat'', ''Bhatmash'', ''Kalitur'' or ''Kala Hulga''. These indigenous varieties are characterised by small black seeds, the ability to thrive well under suboptimal conditions, good seed germinability and organoleptic suitability for certain indigenous food preparations. However, they show low yield, long duration, high pod-shattering, vulnerability to insect-pests and diseases. Dry seeds of the variety ''Bhat'' were treated with gamma rays (15, 20 and 25 k) with and without additional exposure to UV (2 hours at 260 nm). In M₂, the frequency of viable mutations ranged from 0.42 to 5.64%. Both macro- and micro-mutations were identified in the M₂ and M₃ generations. Agronomically useful mutants were evaluated in replicated trials for three consecutive years. A mutant ''T₁54'', resulting from 20kR + UV, surpassed the parent and local checks in yield. Besides, the mutant has other improved desirable attributes viz., yellow seed coat, early maturity (110 days) and tolerance to yellow mosaic and bacterial pustules. The mutant has retained the good seed viability and tolerance to stress conditions as observed in the parent. It is semi-determinate in nature and possesses white flowers in contrast to purple flowers found in the parent variety ''Bhat''. This mutant, later named ''NRC-1'', was entered in the multi-locational varietal trials under the All-India Co-ordinated Research Project on Soybean in 1988. It has faired well in three zones to enmerit its promotion for large scale evaluation in the northern plain zone, the central zone and the southern zone. It has yielded up to 3.64 t/ha at Parbhani in the Central Zone. (author)