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The popular Joha rice cultivar Kon Joha, cultivated throughout the state, was used to induce mutations. Kon Joha is short-grain aromatic rice with excellent cooking quality. The cultivar is tall and late maturing with an average yield of less than 2 tons ha−1 and is susceptible to lodging The investigation through M1 to M3 generation aimed at improving the morpho-agronomic traits of the popular Joha rice cultivar Kon Joha. The experiments were carried out during the Sali season (winter rice) from 2017 to 2019 at Instruction-cum-Research (ICR) Farm of Assam Agricultural University, Jorhat (Assam). Dry uniform seeds of Kon Joha were subject to irradiation with 100–400 Gy of gamma rays from a 60Co source. The M1 generation used a randomized complete block design with four replications during Sali 2017. A total of 5998 M1 plant progenies were subject to screening in the M2 during Sali 2018. The M3 included 662 morpho-agronomic variants raised in the plant rows during Sali 2019, and 66 mutants were confirmed. The M1 of Kon Joha registered a reduction in germination, seedling height, pollen/spikelet fertility and plant survival at 400 Gy. All the traits showed highly significant differences among the doses in the M2 generation. The shift in trait means was in both directions as influenced by the genotype and mutagen dose. The 66 mutants exhibited significant differences for all traits in the M3 generation. Fifty mutants were shorter than the parent Kon Joha. The GCV and PCV estimates were high (>20%) for grain yield, biological yield, productive tillers, filled grains, and average panicle weight. All the traits except panicle length exhibited high heritability coupled with high genetic advance, suggesting the predominance of additive gene action and the effectiveness of simple selection. Grain yield showed a significant positive correlation with plant height, panicle length, filled grains, spikelet fertility, the average panicle weight and harvest index in the mutant population. Thus, mutation induction in Kon Joha proved useful in inducing desirable changes in plant architectural traits. The study further emphasized the short stature high yielding mutants with strong aroma for wide-scale testing in the state. [ABSTRACT FROM AUTHOR]