Mutagenic-sensitivity and variability in the putative mutants of polyembryonic mango genotypes

Polyembryonic mango genotypes are considered the best resources for developing rootstocks owing tothe production of uniform, true-to-type nucellar seedlings with the deep tap root systems. However, their use inbreeding programmes is often limited by a narrow genetic base due to maternal inheritance. Hence, enhancementin or creation of variability for traits of interest becomes a pre-requisite, if rootstock breeding in mango has tobe undertaken. In this study, we attempted to induce variability in polyembryonic mango genotypes, Bappakkai,Nekkare and Kurukkan by treating their kernels with different doses of gamma rays ranging from 15 to 35 Gy.The results revealed delayed germination and a decrease in germination percentage with increasing dosageof gamma irradiation. The lethal dose (LD50) values for gamma radiation were determined, based on the seedgermination percentage using Probit analysis values, which were 22.39 Gy, 19.95 Gy, and 19.95 Gy for Bappakai,Nekkare and Kurukkan, respectively. Other traits like the number of seedlings emerging per kernel, plant height,inter-nodal length, and the number of leaves showed a gradual decrease in their mean values with increasingirradiation dosage. The results suggest the effectiveness of induced mutation in bringing about variability intraits like plant height for developing dwarf rootstocks to be used in high-density planting.