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Applications of molecular markers in bread wheat breeding for pest and disease resistance. The development in recent years of DNAmarkers offers the possibility of developing new approaches to improving the efficiency of selection strategies. The molecular markers are becoming essential tools in bread wheat (Triticum aestivum L.) breeding since they offer alternative solutions to many breeding problems resulting from the traditional phenotypic markers that are difficult and/or time-consuming to select by plant breeders. Availability of tightly linked molecular markers can now be used in markerassisted selection (MAS) programs, specially for disease and pest resistance gene where it is possible to infer the gene by the marker without depending on the natural pest or pathogen occurrence or waiting for its phenotypic expression. Moreover, these markers have potential importance in facilitating selection procedure, particularly for pyramiding two or more different genes aiming at a more durable and broad- spectrum resistance. Breeding for disease and pest resistance gene can contribute to improving quality yield in wheat plants by carrying out indirect selection through molecular markers linked to the traits of interest. We first provide a brief description of main molecular markers technologies currently being employed. Next, we review some of the current and potential uses of molecular markers in breeding for disease and pest resistance genes in bread wheat

With 2 figures and 3 tables Gossypium australe F. Muell (2n = 2x = 26) is a wild perennial species possessing agronomic useful traits that would be interesting to introgress into G. hirsutum L. (2n = 4x = 52), the main cultivated cotton species. To isolate monosomic alien addition lines (MAALs) of G. australe in G. hirsutum, the [2(G. hirsutum × G. australe) × G. hirsutum] pentaploid (2n = 5x = 65) was backcrossed as male parent to G. hirsutum. Analysis of 42 BC1 plants and seven alien addition lines, already available, with 150 SSR markers developed from G. hirsutum revealed a cross‐species amplification rate of 100% and a polymorphism rate of 56%. Eighty polymorphic SSR markers generated 87 G. australe‐specific loci that have been assigned by a hierarchical cluster analysis to 13 linkage groups corresponding to the 13 chromosomes of G. australe. Analysis by SSR markers and genomic in situ hybridization of the self‐progeny of disomic alien addition lines, backcross progeny of the pentaploid, allowed the isolation of five new MAALs. [ABSTRACT FROM AUTHOR]

The rheological properties of wheat grains are associated with the composition of the starchy endosperm in high molecular weight (HMW) glutenin proteins. The HMW glutenin 1xDy12 subunit gene was co introduced with the screenable bar and the reporter gus marker genes in the commercial spring wheat Minaret cultivar (cv). The gene of interest and the marker genes were carried by two separated plasmids, the pBS10BH1 and the pAhC25 respectively. Seven days old calli initiated from immature embryos were bombarded by use of the PDS-1000/He device. A number of different bombardment and culture conditions were tested. These parameters were evaluated on the basis of GUS transient expression. Among those a 4 degrees C cold pre-treatment of the spikes before immature embryos were excised, the culture medium incorporating activated charcoal, silver nitrate and glucose yielded higher GUS transient expression rate. The selective agent bialaphos was maintained at various stages during culture from induction of somatic embryogenesis to rooting of regenerated plantlets. 137 bialaphos resistant plants were obtained among which 109 were carried to maturity. Transgenic plants were characterized by PCR, Southern and SDS-PAGE analysis of the glutenin content.

Overexpression of the budding yeast RAS2 gene in Nicotiana plumbaginifolia cells revealed that RAS2 acted as 'suicide' gene in freshly isolated protoplasts from leaves and blocked cell proliferation in cell suspension-derived protoplasts. Among a series of genes tested (such as npt II, CDC35, PDE2), RAS2 was the only one to block the expression of the cat gene, as measured in a transient gene expression assay. Another ras gene, v-Ha-ras, had similar effects. Furthermore, the RAS2 effect was species-specific and depended on the modulation of hormonal metabolism in the transfected cells, while no differences were noticed between the normal and the activated val19 gene. Transfected plant cells are shown to synthesize a RAS2 protein of the same electrophoretic mobility as the yeast RAS2 product. The results are discussed in the broader context of the evolutionarily conserved ras genes involved in vital cellular functions.

The gene of Saccharomyces cerevisiae responsible for adenylate cyclase activity was cloned by complementation of a thermosensitive tsm0185 mutation in yeast; it was also shown to complement the yeast cyr1 mutation. Preliminary results indicate the presence of a repeated sequence on the same genomic fragment.