A method for extraction of high quality DNA from four Opuntia sp. and other cacti using a hexadecyltrimethylammonium bromide (CTAB) method is described. These plants typically contain high levels of mucilages, complex polysaccharide compounds that bind water, thus preventing DNA extraction by common miniprep methods. The method involves adjusting the amount of tissue used according to species and age, followed by processing in an extraction buffer to separate coarse material. Extended centrifugation and digestion time in a separation buffer with CTAB (2%) was used. Exposing tissue to both buffers maintained polysaccharides in solution and allowed easier recovery of the aqueous phase that contains the DNA. We found that 5-8 g were needed to obtain up to 153 μg·g-1 of DNA from tender tissue. Old tissue yielded 26% less. Extraction of DNA from 5-g samples of tender tissue of the ornamental cacti Stenocereus sp., Cleistocactus sp., and Echinocereus sp. was successful. For these species, average yields ranged from 25 to 53 μg per sample. The DNA obtained was suitable for polymerase chain reaction (PCR) amplification, producing clear, distinctive, and reproducible banding patterns useful for a variety of applications.
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