A procedure has been developed for rapidly inoculating large numbers of turnip seedlings with Xanthomonas campestris pv. campestris, the causal agent of black rot of crucifers. Following mutagenesis bacterial mutants were isolated which showed altered pathogenicity. The mutants gave a range of responses on plants and some were impaired in their ability to grow in seedlings.

A DNA sequence between two legumin genes in Pisum is a member of the copia-like class of retrotransposons and represents one member of a polymorphic and heterogeneous dispersed repeated sequence family in Pisum. This sequence can be exploited in genetic studies either by RFLP analysis where several markers can be scored together, or the segregation of individual elements can be followed after PCR amplification of specific members.

We have employed a combination of techniques to examine the organization of pea 5S rRNA genes. These include the analysis of length variant interspersion patterns in cosmid clones, sequence analysis, Southern analysis of both conventional gels and field inversion gels and in situ hybridization. From these analyses we conclude that the 5S rRNA genes of pea are arranged in three major tandem arrays which are represented by three large EcoRI fragments and that these correspond to the three sites of in situ hybridization in the haploid pea complement.

We describe four genomic clones of pea 7S storage protein gene, one of which corresponds to convicilin, and the others to vicilin. Hybridization studies exploiting these clones, and previously identified eDNA clones, have enabled us to define six different loci. Three of these loci have been mapped to positions on chromosome 7.

The highly repetitive sequences of the flax genome have been characterized. This has been done using a series of cloned probes that represent most, if not all, of the highly repetitive families in the flax genome. All of them are arranged as tandem arrays. The organization and copy number of these sequences has been compared in a number of lines including those lines (termed genotrophs) derived from the flax variety 'Stormont Cirrus' by the environmental induction of heritable changes, two other flax and linseed cultivars, and some of the supposed wild progenitors of flax. It was found that all except the light satellite differed in copy number between some of the lines. A particular subset of the 5S genes was shown to be preferentially affected when changes occurred. The extent of the variation between genotrophs was similar to that between different varieties or between flax and its supposed progenitor.Key words: flax, DNA variation, repeated sequences.