[Diversity of Frankia in nodules of Alnus nepalensis at Gaoligong Mountains revealed by IGS, PCR-RFLP analysis].

30 nodule samples were used to assess the diversity of Frankia strains symbiotically associated with Alnus nepalensis naturally occurring at the Gaoligong Mountains in Yunnan Province, China. DNA was extracted directly from nodules, and its two target DNA regions that encode nifD-nifK intergenic spacer (IGS) and 16S-23S rDNA IGS was studied by PCR-RFLP. The PCR fragments yielded by the nifD-nifK IGS were noticeably different in size, and when they were digested by Hae III and Afa I, 15 nif-type Frankia strains could be detected, the PCR-RFLP result of this region also could show that more than one genotype Frankia strains could form symbiosis with individual plants at the same time. The 16S-23S rDNA IGS had similar PCR fragments, but still identified 15 rrn-type strains after digested by Hae III and Afa I. 20 genotype strains could be found only when combined the PCR-RFLPs of two target regions.