18239
In addition , we used a PCR assay with ITS specific primers to amplify multiple ITS variants for collections assignable to C . americana indicating that there is genetic variability within ITS copies most likely due to introgression , crossing over and / or the retention of ancestral variants .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
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