Mutagenic effects of chemical and physical mutagens on mitotic chromosomes in Brassica juncea (L.) cv. Bio-902

Abstract

The present study reveals the mitotic index frequency and mitotic abnormality frequency of various mutagenic treatments.
True to type pre-soaked seeds of Brassica juncea (L.) cv. Bio-902 were treated with different concentrations of chemical
mutagens; sodium azide (SA), ethyl methane sulphonate (EMS) and physical mutagen; gamma radiations. Mutagen
doses were determined based on LD50. Doses for gamma rays’ treatments were 800Gy, 1000Gy and 1200Gy. The
concentrations for the dry seed treatments of SA and EMS were 0.003%, 0.006% and 0.009% for each mutagen. The
concentrations of pre-soaked treatments for 12 hrs and 18 hrs of both chemical mutagens were 0.04%, 0.08% and 0.12%.
Various mitotic abnormalities like clumping of prophase and metaphase, stickiness, laggards, single, double and multiple
bridges, distorted anaphase, multi-spindle anaphase, fragment, diagonal arrangement, and unequal separation were
observed. Mitotic index and abnormality frequency were computed by scoring the somatic cell. Mitotic study provides
idea about the effectivity of mutagens and confirms about mutation. The study helps researcher to confirm about the
doses determined and predict the direction of mutation.