Identification of collembolan species is generally based on specific morphological characters, such as chaetotaxy and pigmentation pattern. However, some specimens do not match to described characters because these refer to adult specimens, often of one specific sex, or the characters are highly variable in adults (e.g. pigmentation, setae or furcal teeth). Isozymes have frequently assisted species discrimination, and also these may vary with developmental stage or environmental conditions. For identification of single species of the Isotoma viridis group, we present both direct sequencing of the cytochrome oxidase subunit II (COII) gene and a simple DNA-based molecular method.
Five PCR primers amplifying the COII region (717 bp) of the mitochondrial DNA were used. The sequences clearly separated the species I. viridis, I. riparia and I. anglicana, irrespective of colour varieties within the first species. DNA amplification products of different species can also be distinguished by digestion with restriction endonucleases, followed by gel electrophoresis for separation of fragments. This restriction fragment length polymorphism (RFLP), obtained after digestion with the endonucleases TaqI, VspI, MvaI and Bsp143I, revealed specific fragments that separated the three species from each other. Since restriction enzymes are sensitive to single base mutations, we suggest to use a combination of enzymes with at least two species-specific restriction sites when using the RFLP technique. For the I. viridis complex, VspI and Bsp143I appear to be an appropriate combination. 相似文献
The potential use of the Randomly Amplified Polymorphic DNA (RAPD) technique for characterization and assessment of genetic
relationships was investigated in nineteen walnut (Juglans regia L.) genotypes used as parents or released as cultivars from
the breeding program of the University of California at Davis. Most of the 72 decamer primers used yielded scorable amplification
patterns based on discernable bands. The results obtained produced a unique fingerprint for each of the walnut genotypes studied.
Cluster analysis separated the 19 walnut genotypes into two main groups whose differences were related to their pedigree.
Genotypes sharing common parents tend to group together and with at least one of the parents. Thus, RAPD markers can detect
enough polymorphism to differentiate among walnut genotypes, even among closely related genotypes, and the genetic similarity
based on RAPDs appears to reflect the known pedigree information. RAPD technology can be useful in current walnut breeding
programs, allowing the identification of new cultivars as well as the assessment of the genetic similarity among genotypes
which will help in selecting the best parents to obtain new genetic combinations.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献