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

Abstract

Polyembryonic mango genotypes are considered the best resources for developing rootstocks owing to the production of uniform, true-to-type nucellar seedlings with deep tap root systems. However, their use in breeding programmes is often limited by a narrow genetic base due to maternal inheritance. Hence, enhancement in or creation of variability for traits of interest becomes a pre-requisite if rootstock breeding in mango has to be 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 dosage of gamma irradiation. The lethal dose (LD50) values for gamma radiation were determined based on the seed germination 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 gradually decreased their mean values with increasing irradiation dosage. The results suggest the effectiveness of induced mutation in bringing about variability in traits like plant height for developing dwarf rootstocks to be used in high-density planting.