Species, Their Diversity and Populations 201 Table 13.3 Variation in Fungal Populations

Species Data type Geographic scale populations isolates

Agaricus bisporus RFLP Intercontinental 2 342

Mycosphaerella graminicola RFLP Local 3 512

Neurospora intermedia Allozyme Intercontinental 4 145

Schizophyllum commune Allozyme Intercontinental 7 136

13.6.4 Ribosomal DNA

The nuclear ribosomal coding cistron (rDNA) has been widely utilized for detecting variation among isolates of a fungus. The rDNA is composed of tandemly repeated units, each unit being composed of 5S, 25S and 18S rDNA (Figure 13.5). Two noncoding regions exist in each repeat, the internal transcribed spacer (ITS1 and ITS2) and an intergenic non-transcribed spacer (NTS). The NTS can be preferentially amplified by PCR using primers, cut with restriction enzymes and the RFLPs separated by electrophoresis and compared.

Figure 13.4 RAPDs in ten random isolates of Erysiphe graminis f.sp. hordei sampled from a single population using two different 10-base primers (above and below). (From McDonald and McDermott (1993). With permission of the publisher.)
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