Effects of acute and chronic gamma irradiations on regeneration of tissue types from selected Ugandan cassava genotypes.

Acute and chronic gamma irradiations (ACGIs) has facilitated generation of new varieties that can withstand abiotic and biotic stresses. This study examined the impact of ACGI doses on the regenerative ability of in vitro embryogenic tissues into complete plants. Tissues from nine genotypes (Alado, NASE 13, NASE 19, NAROCASS 1, CV_193, CV_98/0505, CV_60444, BAO, and reference Ubi Putih) were subjected to acute gamma irradiation (AGI) across six dose levels (0, 5, 10, 15, 20, 25, 35 Gy). Five genotypes (Ubi Putih, CV_60444, Alado, NASE 13, NAROCASS 1) were exposed to chronic gamma irradiation (CGI) for one to four weeks. Ten explants per genotype per dose were evaluated. Mean shoot length was used to calculate the growth reduction dose (GR50), and cell structure changes were analyzed using hematoxylin and eosin staining. Exposure of tissues to AGI and CGI enhanced shoots, roots, leaf regeneration as well as shoot length at dose rates of 5-20 Gy (AGI) and 46 Gy (CGI) at twoweeks. The calculated GR50 varied across genotypes and irradiation types. Histological analysis confirmed that distinct structural changes in cell and tissue morphology were linked to irradiation exposure. These results demonstrate that ACGIs can induce accelerated regeneration and structural variation in embryogenic cassava tissues, revealing the potential to develop novel varieties with improved stress resilience. The study underscores ACGIs as a viable biotechnological tool in mutation breeding and genetic improvement of root crops.