Sequence-Dependent Fluorescence of Cyanine Dyes on Microarrays

Cy3 and Cy5 are among the most commonly used oligonucleotide labeling molecules. Studies of nucleic acid structure and dynamics use these dyes, and they are ubiquitous in microarray experiments. They are sensitive to their environment and have higher quantum yield when bound to DNA. The fluorescent intensity of terminal cyanine dyes is also known to be significantly dependent on the base sequence of the oligonucleotide. We have developed a very precise and high-throughput method to evaluate the sequence dependence of oligonucleotide labeling dyes using microarrays and have applied the method to Cy3 and Cy5. We used light-directed in-situ synthesis of terminally-labeled microarrays to determine the fluorescence intensity of each dye on all 1024 possible 5′-labeled 5-mers. Their intensity is sensitive to all five bases. Their fluorescence is higher with 5′ guanines, and adenines in subsequent positions. Cytosine suppresses fluorescence. Intensity falls by half over the range of all 5-mers for Cy3, and two-thirds for Cy5. Labeling with 5′-biotin-streptavidin-Cy3/-Cy5 gives a completely different sequence dependence and greatly reduces fluorescence compared with direct terminal labeling

The role of Schmidt 'Antonovka' in apple scab resistance breeding

'Antonovka' has long been recognised as a major source of scab (Venturia inaequalis) resistance useful for apple breeding worldwide. Both major gene resistances in the form of the Rvi10 and Rvi17 and quantitative resistance, collectively identified as VA, have been identified in different accessions of 'Antonovka'. Most of the 'Antonovka' scab resistance used in apple-breeding programmes around the world can be traced back to Schmidt 'Antonovka' and predominantly its B VIII progenies 33,25 (PI 172623), 34,6 (PI 172633), 33,8 (PI 172612) and 34,5 (PI 172632). Using genetic profile reconstruction, we have identified "common 'Antonovka' " as the progenitor of the B VIII family, which is consistent with it having been a commercial cultivar in Poland and the single source of scab resistance used by Dr. Martin Schmidt. The major 'Antonovka' scab resistance genes mapped to date are located either very close to Rvi6, or about 20-25 cM above it, but their identities need further elucidation. The presence of the 139 bp allele of the CH-Vf1 microsatellite marker known to be associated with Rvi17 (Va1) in most of the 'Antonovka' germplasm used in breeding suggests that it plays a central role in the resistance. The nature and the genetic relationships of the scab resistance in these accessions as well as a number of apple cultivars derived from 'Antonovka', such as, 'Freedom', 'Burgundy' and 'Angold', are discussed. The parentage of 'Reglindis' is unclear, but the cultivar commercialised as 'Reglindis' was confirmed to be an Rvi6 cultivar