A restriction fragment length polymorphism (RFLP) map for the A genome of Avena has been developed using F3 families from the cross A. atlantica × A. hirtula. The main source of markers were an oat cDNA and a barley cDNA library. A total of 194 RFLP markers was used, 192 of which were mapped or assigned to linkage groups. Seven main linkage groups, presumably corresponding to the seven chromosomes of the haploid genome, were identified. The linkage groups varied in size from 30 to 118 cM for a total map length of 614 cM. This map provides a tool for the interpretation of genome organization in Avena and for marker selection in the development of a map of hexaploid oats.Key words: restriction fragment length polymorphism, Avena, mapping.

Eleven pea mutants, displaying a greatly reduced number of root nodules or lacking such nodules completely, were obtained by screening the M 2 progeny of mutagenized Pisum sativum cv. Sparkle. The mutant alleles conditioning the altered nodulation phenotypes were recessive to the wild-type alleles. Eight of the mutants possessed a normal growth habit except for the complete lack of nodules. Pairwise crosses among these mutants indicated that five distinct loci had been affected. The remaining three mutants formed few nodules and also had altered root or shoot growth habit. Each of these pleiotropic mutants was coded by a distinct gene. The eight genes identified are designated sym7, sym8, sym9, sym10, sym11, sym15, sym16, and sym17, signifying their involvement in the pea/Rhizobium symbiosis. The locations of most of these sym genes were determined by classical linkage mapping. The loci were distributed on at least five of the seven chromosomes.

Treatment of Pisum sativum (L.) cv 'Sparkle' with ethylmethane sulfonic acid produced a stable mutant, E107, which forms few nodules. The mutant allele exhibits other pleiotropic properties including bronze necrotic spots on the leaflets and high accumulation of iron in the shoot. The mutant phenotype is under monogenic recessive control. The gene, designated brz (bronze), is nonallelic with two other genes conditioning necrotic spots on leaves of other mutants of P. sativum. The brz allele was located on chromosome 4 by linkage with wax production controlled by alleles at the was locus.notably iron which is elevated over fifty-fold above that of the normal parent 'Sparkle' (18). A similar accumulation of iron in pea leaves is reported in the disease purple blight (16), which may occur after prolonged waterlogging of soils. A survey of a Pisum collection revealed accessions with necrotic leaves similar to those of E107. These lines were phenotypically compared and crosses among them were analyzed for genetic complementation. We report here that mutant E107 carries a new gene, designated brz (bronze), associated with decreased nodulation, increased iron uptake and bronze leaf spots in P. sativum. MATERIALS AND METHODS PlantsThe genetic contribution of the host plant to nodule formation is not as well documented as that of the microsymbionts. To

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