Biomedical subjects

D Danesh

Publications and source records attributed to D Danesh.

4 recordsLinked to original sources

PubMed2001

Soybean genomic survey: BAC-end sequences near RFLP and SSR markers.

We are building a framework physical infrastructure across the soybean genome by using SSR (simple sequence repeat) and RFLP (restriction fragment length polymorphism) markers to identify BACs (bacterial artificial chromosomes) from two soybean BAC libraries. The libraries were prepared from two genotypes, each digested with a different restriction enzyme. The BACs identified by each marker were grouped into contigs. We have obtained BAC- end sequence from BACs within each contig. The sequences were analyzed by the University of Minnesota Center for Computational Genomics and Bioinformatics using BLAST algorithms to search nucleotide and protein databases. The SSR-identified BACs had a higher percentage of significant BLAST hits than did the RFLP-identified BACs. This difference was due to a higher percentage of hits to repetitive-type sequences for the SSR-identified BACs that was offset in part, however, by a somewhat larger proportion of RFLP-identified significant hits with similarity to experimentally defined genes and soybean ESTs (expressed sequence tags). These genes represented a wide range of metabolic functions. In these analyses, only repetitive sequences from SSR-identified contigs appeared to be clustered. The BAC-end sequences also allowed us to identify microsynteny between soybean and the model plants Arabidopsis thaliana and Medicago truncatula. This map-based approach to genome sampling provides a means of assaying soybean genome structure and organization.

Algorithms↗

PubMed1992

Evidence for orthologous seed weight genes in cowpea and mung bean based on RFLP mapping.

A well saturated genomic map is a necessity for a breeding program based on marker assisted selection. To this end, we are developing genomic maps for cowpea (Vigna unguiculata 2N = 22) and mung bean (Vigna radiata 2N = 22) based on restriction fragment length polymorphism (RFLP) markers. Using these maps, we have located major quantitative trait loci (QTLs) for seed weight in both species. Two unlinked genomic regions in cowpea contained QTLs accounting for 52.7% of the variation for seed weight. In mung bean there were four unlinked genomic regions accounting for 49.7% of the variation for seed weight. In both cowpea and mung bean the genomic region with the greatest effect on seed weight spanned the same RFLP markers in the same linkage order. This suggests that the QTLs in this genomic region have remained conserved through evolution. This inference is supported by the observation that a significant interaction (i.e., epistasis) was detected between the QTL(s) in the conserved region and an unlinked RFLP marker locus in both species.

Fabaceae↗

PubMed1979

Toxic aspergilli from pistachio nuts.

Pistachio nut samples taken during various stages of development from orchards in Iran, showed that contamination with fungi occurred mainly during the later stages of nut development. Members of the genera Aspergillus and Penicillium occurred most frequently. Of the Aspergilli, the species A. niger, A. flavus and A. fischeri var. spinosus occurred most frequently, followed by A. terreus, A. tamarii and A. nidulans. Twenty-two isolates comprising 13 species were tested for toxicity to ducklings. Isolates of known toxic fungi included A. flavus, A. niger, A. parasiticus, A. ochraceus, A. versicolor, A. nidulans and A. terreus. The toxicity of A. fischeri var. spinosus is reported. Chemical analysis showed that all isolates of A. flavus and A. parasiticus produced aflatoxin B1, the isolates of A. versicolor and A. nidulans produced sterigmatocystin while the toxic isolate of A. ochraceus did not produce ochratoxins.

Aflatoxins↗

PubMedDate not supplied

Genetic dissection of oligogenic resistance to bacterial wilt in tomato.

To study resistance to bacterial wilt (caused by Pseudomonas solanacearum) in tomato, we analyzed 71 F2 individuals from a cross between a resistant and a susceptible parent with 79 DNA markers. F2 plants were inoculated by two methods: bacteria were injected into shoots of cuttings or poured into soil surrounding wounded roots. Disease responses were scored on a scale of 0 to 5. Statistical comparisons between DNA marker genotypes and disease phenotypes identified three genomic regions correlated with resistance. In plants inoculated through roots, genomic regions on chromosomes 6 and 10 were correlated with resistance. In plants inoculated through shoots, a region on chromosome 7 was significant, as were the regions on chromosomes 6 and 10. The relative impact of resistance loci on disease response differed between shoot and root inoculations. To confirm the existence of a partial resistance gene on chromosome 6, an F2 individual homozygous for the resistant parent's alleles on chromosomes 7 and 10, but heterozygous for markers on chromosome 6, was selfed. Analysis of the F3 progeny confirmed that a partial resistance locus was located on chromosome 6, very close to CT184. The presence of a partial resistance locus on chromosome 10 was similarly confirmed by analysis of progeny of another F2 plant chosen on the basis of its marker phenotype.

Chromosome Mapping↗