Lack of adequate water leading to drought stress is a common constraint in upland cultivation system ofrice. a rice mutant line (MT58) was developed in previous research after mutagenesis of cv. Neda by ethylmethane sulfonate (EMS) and selected for dwarfism (18 cm shorter than Neda). The extent of its molecularchanges relative to parental cultivar was assessed by SSR and ISSR markers, and the response of the linealong with parental cultivar and another mutant line (MTA) to mild and severe water

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... deficit, was evaluated ina field experiment. a molecular assessment by using 41 SSR markers showed that stunt line MT58 had significantmolecular difference with two other lines as confirmed by cluster analysis. ISSR assay also proved theconsiderable mutational effect of EMS on two mutant lines compared to original wild line. Field experimentsrevealed that limited irrigation caused mild to severe decrease in all the studied traits including chlorophyllcontents. In both mild and sever water stress (S1 and S2) dwarf mutant MT58 had not significant differencesin plant yield from parental cultivar Neda. In mild water stress cultivar Neda and mutant line MT58, respectively,showed highest (14%) and lowest (3%) yield loss, while in sever water stress mutant lines MTA andMT58, respectively, showed highest (33%) and lowest (19%) yield loss. In severe stress, cultivar Neda hadhighest plant height, tiller number and plant yield, and mutant MT58 had highest panicle length, total kernelsper panicle, fertile kernels and chlorophyll contents. Reduction in chlorophyll content at drought stress conditionwas correlated with yield loss (0.64 and 0.697 for chl.a and chl.b, respectively). The results of this researchobviously confirm that mutant line MT58 despite of its stunt figure did not show yield difference fromits parental cultivar in drought stress.