Cauliflower somatic embryogenesis and analysis of regenerant stability by ISSRs

  To study the somatic embryogenesis of Brassica oleracea var. botrytis L., hypocotyls were placed on Murashige and Skoog's medium (1962) with 1 mg.l^–1 of 2,4-dichlorophenoxyacetic acid and 1 mg.l^–1 of kinetin to induce callogenesis. After transfer of the calli to the maturation medium, somatic embryos appeared. They developed into plantlets and the potential of regeneration of the calli was maintained for more than 8 months. Thirty-five plantlets were produced after 2 months of culture, then transplanted into soil. Inter-simple sequence repeat markers generated by trinucleotidic and tetranucleotidic primers were tested for their ability to characterise genomic variations in the obtained plants. The absence of polymorphism between different regenerants from the same cultivar indicates the conformity of the regeneration protocol. Received: 4 February 2000 / Revision received: 22 May 2000 / Accepted: 23 May 2000     

Detection of T-DNA transfer to plant cells by A. tumefaciens virulence mutants using agroinfection

Summary To test whether virulence mutants of Agrobacterium tumefaciens are capable of promoting T-DNA transfer into plant cells, a tandem array of Cauliflower Mosaic Virus (CaMV) DNA was cloned between T-region border sequences on a wide host range plasmid and introduced into various virulence mutants. The resulting strains were used to infect Brassica rapa cv. Just Right. This assay, recently referred to as agroinfection, is based on the appearance of viral symptoms following transfer of T-DNA to plant cells, and is shown to be at least 100 times more sensitive in detecting T-DNA transfer than tumour formation. Mutants in the loci vir A, B and G, which were avirulent on turnip, failed to induce virus symptoms. Of the two vir D mutants tested, neither induced tumours, but one was capable of inducing virus symptoms. Mutants in vir E, C and F, which induced respectively no, small and normal tumours on turnip, all induced virus symptoms.