Isolation and characterization of nitrate reductase-deficient cell lines from a haploid culture of peony.

Abstract

Six chlorate-resistant (CR) cell lines were established from survivors after plating mutagenized and non-mutagenized cells of Kp20, a Paeonia haploid cell line, onto solid medium containing 30 mM KCIO3 and amino acids as the sole nitrogen source (AA-chlorate medium).Five millimolar N-ethyl-Nnitrosourea (ENU) was used as the mutagen. None of the 6 CR lines grew on medium containing nitrate as the sole nitrogen source (N03-medium). Of these CR lines, 5 completely lacked in vivo nitrate reductase (NR) activity and one showed low (about 11% of that of the wild type) NR activity.In all CR lines except for one, the percentage occupied by haploid cells increased to 83-95% compared with 73% in the wild type. This suggested that mutation may have occurred to advantage in the haploid cells.