EMS Induction of Early Flowering Mutants in Spring Rape (Brassica napus)

Abstract

AbstractStudies were undertaken to induce early flowering mutants by ethyl methanesulphonate (EMS) treatments of Brassica napus seeds. EMS treatments for 12 h of a highly inbred B. napus line TBS had adverse effects on M1 plant development and fertility only when concentrations were greater than 1%. However, an EMS concentration of 1.5% did not reduce M1 plant fertility to an extent which significantly reduced production of M2 seeds.Genetic changes induced by EMS treatment and affecting flowering time were of three main types: (1) Changes within a polygenic system reflected by increased variation in flowering time among M2 families. As the increase in variation was due primarily to a higher frequency of later flowering plants, these polygenic changes would be of little value in developing better‐adapted cultivars. (2) Induction of a recessive mutation at a major gene locus which caused M3 plants homozygous for the mutant gene to flower at least 20 days earlier than the parental line TB8. (3) Induction of a dominant mutation at a major gene locus which affects flowering time by causing a substantial reduction in vernalization requirement. M2 plants carrying the mutant gene flowered as early as 59 days before the parental line.These major gene mutations could be rapidly exploited in the development of agronomically superior cultivars for short‐season, lower rainfall environments in Western Australia.