Chromosome behaviour and formation of micronuclei after treatment of cell suspension cultures with amiprophos-methyl in various plant species

Abstract

Chromosome behaviour and the formation of micronuclei after treatment of cell suspensions of Solanum tuberosum, Daucus carota and Haplopappus gracilis with the microtubule depolymerizing herbicide amiprophos-methyl (APM) are reported. The addition of APM at 32 and 64 μM to suspension cells resulted in a high degree of metaphase arrest, and single as well as groups of two or more chromosomes were scattered throughout the cell offering good prospects for cytology and metaphase chromosome isolation. The course of mitosis was strikingly different from normal. Metaphase chromosomes showed no centromere division or separation of chromatids (devoid of anaphase). The single as well as grouped metaphase chromosomes started decondensation after a 3-h application of APM and within 10 h they developed nuclear membranes and formed micronuclei. The frequency of APM-induced micronucleation varied according to the species, cell growth and mitotic activity. Fast-growing cell cultures responded with higher frequency of micronucleate cells than the relatively slow-growing cultures. After removal of APM, chromosome grouping and micronucleation disappeared and cells showed normal mitosis and growth. Various factors related to cell cycle progression, mitotic index and cell growth which are important for increasing micronucleation, are discussed. The application of micronuclei for partial genome transfer and gene mapping in plants is suggested.