Genetic variability amongNosema apisisolates

SUMMARYGenetic variability in the ribosomal RNA genes and the associated spacer regions of Nosema apis was investigated in 13 New Zealand isolates and 12 isolates obtained from around the world. Comparisons of banding patterns, obtained by gel electrophoresis of polymerase chain reaction products amplified from the start of the intergenic spacer revealed marked variation among the isolates. No differences were found among samples collected sequentially from particular colonies in New Zealand, nor among samples developed to minimize genetic diversity for further experiments. DNA sequence data were obtained from around the internal transcribed spacer and from the 3' end of the large subunit rRNA gene. No sequence variation was observed within or around the internal transcribed spacer. Only two singlebase differences were identified in the DNA sequence from the large subunit rRNA gene; one in an isolate from Brazil and one in an isolate from Israel. The consequences of the variation observed are discussed.