Mapping the genome of Eimeria tenella: use of a yeast artificial chromosome library as the basis for a physical map.

Efforts to derive a physical map of the genome of Eimeria tenella are being made to complement genetic mapping and to assist in the production of an integrated map. A large insert library of DNA from the Houghton (H) reference strain of E. tenella has been constructed in yeast artificial chromosomes (YACs). The library contains a tenfold E. tenella genome equivalent consisting of 3177 clones arrayed in 96-well microtitre plates and gridded on nylon membranes at 1728 clones/86 cm2. Size fractionation of a random sample of 185 YACs revealed an average insert size of approximately 170 kb. Hybridisation of four E. tenella single-copy probes to the gridded colony filters produced around four or more positive clones. A probe representing the whole of the 1.2-Mb chromosome 2, excised from a preparative gel following pulsed-field gel electrophoresis, revealed between 80 and 100 positive clones.