Chromosome Structural Rearrangements in Onion (Allium cepa L.) through Induced Mutation

Abstract

This study investigated whether there was any chromosomal structural rearrangement in individual chromosome of two mutant lines of onion viz., BP2-100/1 and BP2-100/2 compared to the parental chromosomes which may explain the seed to seed productions of the mutants in the same winter season even at late planting in January unlike the parent variety. The chromosome preparation was made from the root tip by haematoxylin method. No deviation in the number of chromosomes was found in the mutant lines but the length of the individual chromosomes was longer than that of their parent variety. Out of the eight pairs of homologous chromosomes, seven pairs were metacentric and one pair submetacentric in the parent “BARI Piaz-2”; five pairs were metacentric and three pairs submetacentric in BP2-100/1; and three pairs were metacentric, three pairs submetacentric and two pairs of subtelocentric in BP2-100/2. It was assumed that the length extension of the chromosomes and rearrangements in the arm ratio were due to gamma irradiation that induced duplication and or translocations of some regions of the chromosomes. Further research is needed to identify the induced genes and to establish relationships of the genes with the modified seed production behavior of the mutants.