Summary Mutagenic effectiveness and efficiency is an important factor for the selection of a mutagen for a mutation breeding program. Mutagenic effectiveness is a measure of the frequency of mutations induced by a unit mutagen dose, while mutagenic efficiency is a measure of the proportion of mutations in relation to undesirable changes such as lethality, sterility, meiotic aberrations etc. The present study envisages the mutagenic effectiveness and efficiency of individual and combined treatments of chemical and physical mutagens i.e. sodium azide (individual), gamma rays (individual) and sodium azide+gamma ray (combined). For the individual treatment of sodium azide, the seeds of the Sesbania cannabina variety nD-1 were treated with 0.5% solution of sodium azide (Sa) for four different time durations, i.e. 3, 5, 7, and 9 h, and for the individual treatment of gamma rays, dry and healthy seeds were treated with 20, 40, 60, and 80 Kr doses of gamma rays. For the combined treatment, the seeds were exposed to four different doses of gamma rays (20, 40, 60, and 80 Kr) and after irradiation seeds were treated with 0.5% solution of sodium azide for 3 h. after treatment, seeds subjected to individual and combined treatment were sown in randomized block design to raise the M 1 generation and a study was conducted on germination percentage, survival percentage, pollen fertility percentage, and chromosomal aberrations at different doses of the individual and combined treatments.

Summary Seeds of Sesbania cannabina cultivar ND-1 were subjected to different doses of gamma irradiation (20, 40, 60 and 80 KR) and irradiation effects on seed germination, survival, and several morphological and cytological characters of adult plants were studied. The irradiated seeds were tested for lethal doses at which 50% of the seeds germinated (LD 50 ) i.e. 40 KR dose. Plants grown from the gamma ray-treated seeds showed variation regarding their morphological and cytological characters. The plant height, stem girth, number of leaves per plant, and pod length decreased as the doses of irradiation increased. However, internode length increased with increasing doses of irradiation. Meiotic analysis revealed the presence of various types of chromosomal abnormalities at all phases. Meiotic aberrations increased according to the doses of irradiation. A reduction in pollen fertility was also noticed.

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