Different genetic groups of Frankia within the root nodules of Casuarina growing in Mexico

Abstract

This study was carried out to examine the possible genetic diversity that may occur among Frankia strains that nodulate C. equisetifolia in Mexico growing in the site of introduction, the cost of the Golf of Mexico, as well in the highlands. DNA extracted from reference cultures of Casuarina infecting Frankia strains, from field collected nodules (two trees of each of 14 sites and 3–5 analyzed lobes of each nodule) or from young nodules obtained from plants growing at the growth chamber and inoculated with field nodules, were used as the template in PCR reaction with primers targeting two DNA regions, one of the ribosomal operon and the other in the nif operon. PCR products were analyzed by using a set of recommended restriction enzymes. Six PCR-RFLP groups were detected after digestion with combination of enzymes BstUI and CfoI of the nif region, and four PCR-RFLP groups with enzymes NciI and ScrFI in the ribosomal region. Reference strains showed similar patterns and were assigned in group 1 along with an uncultured strain. nifD-K PCR-RFLP groups allowed a better understanding of the diversity among nodular Frankia strains than those observed in the rrs PCR-RFLP groups.