XVI International Botanical Congess

The use of morphology to define species boundaries in the genus Pythium can be difficult as characters are variable. PCR amplification of the intergenic spacer of the ribosomal DNA repeat unit and subsequent restriction digestion produces species-specific DNA fingerprints. Pythium diclinum, P. dissotocum, P. aquatile, P. angustatum, P. coloratum, P. pachycaule, and P. lutarium had very similar fingerprints. Restriction digestions using 7 restriction enzymes were done and distance matrices based on the presence or absence of comigrating restriction fragments were constructed for cluster analysis. Results showed clustering of the seven species, suggesting a close evolutionary relationship between them.