Can we predict mutagen-induced damage in plant systems mathematically? Insights from zygotic embryo and haploid mutagenesis in Indian mustard (Brassica juncea)

Th is study was undertaken to determine the relationship between mutagen concentration, exposure duration and survival of zygotic embryos along with evaluation of microspore totipotency of the mutant donor plants of Brassica juncea. Th ree Indian genotypes were tested for varying mutagen concentrations (5-50 mM) and exposure durations (10-50 h) of three chemical mutagens, ethyl methanesulfonate (EMS), ethyl nitrosourea (ENU) and ethidium bromide (EtBr), to study the eff ect of mutagen exposure on zygotic embryos. Th e exposure to EtBr resulted in 100% mortality, however, the survival data for EMS/ ENU analyzed by orthogonal contrast partitioning ANOVA revealed that concentration for both mutagens had a linear relationship with percent survival while exposure duration had a non-linear relationship. Multiple regr ession analysis was used to develop prediction functions for EMS/ ENU treatment survival and the LD 50 for zygotic embryo mutagenesis for 20h duration ranged from 3.5mM for ENU to 6.8mM for EMS. Th is information was used to generate mutant donor plants for microspore culture and 48.8% EMS mutant donor plants produced 2.9 ± 0.4 embryos per Petri dish (total 943 embryos).