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We mapped and characterized quantitative trait loci (QTL) for resistance to Sporisorium reiliana. A population of 220 F(3) families produced from the cross of two European elite inbreds (D32, D145) was evaluated with two replications at a French location with high natural incidence of S. reiliana and at a Chinese location employing artificial inoculation. The 220 F(3) families were genotyped with 87 RFLP and seven SSR markers. Using composite interval mapping, we identified two different sets of 3 and 8 QTL for the French and the Chinese locations explaining 13% and 44% of respectively. Individual QTL explained up to 14% of σ^(2) (p). The 11 QTL mapped to eight maize chromosomes and displayed mostly additive or partial dominant gene action. Significant digenic epistatic interactions were detected for one pair of these QTL. Only a few QTL for S. reiliana were in common with QTL for resistance to Ustilago maydis and Puccinia sorghi, identified at a German location for the same population. Consequently, in our materials resistance to these three fungal pathogens of maize seems to be inherited independently.

The potential of microsatellite sequences as genetic markers in channel catfish (Ictalurus punctatus) was investigated with respect to their variability, inheritance, and usefulness in related species. Six small insert genomic DNA libraries enriched for six families of microsatellites of channel catfish were constructed. We describe here the isolation, characterization, and PCR amplification of 32 microsatellites from channel catfish. The flanking primer regions of microsatellite loci were highly conserved between channel catfish and blue catfish (I. furcatus). Of the 32 loci, 29 were amplified from blue catfish using primers designed from channel catfish, indicating conservation of primer binding sequences. Most of the amplified alleles from channel catfish and blue catfish were polymorphic. White catfish (Ameiurus catus) and flathead catfish (Pylodictus olivaris) loci were also amplified. The microsatellite markers are highly polymorphic for all catfish species tested and are inherited as codominant markers. They should be highly useful for construction of genetic linkage maps of catfish and for marker-assisted selection.

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