Abstract:

We have attempted to use the SRAP (sequence-related amplified polymorphism) markers, a new molecular technology, to study genetic diversity in soil microbes. We sampled rhizosphere soil microbes from 20 plant species and employed 22 SRAP primer combinations. A total of 237 scorable fragments were identified, of which 221 (93.2%) were polymorphic loci. The average percentage of polymorphic loci (PPL), polymorphism information content (PIC), allele haplotype (Ah), and expected heterozygosity (He) for each primer combination were 93.78%, 0.94, 18.05 and 0.92, respectively. Our results revealed rich genetic diversity in rhizosphere soil microbes and the high ability of SRAP to resolve samples based on their genetic basis. Differences in genetic distance for rice rhizosphere microbes between two locations, and that among four different developmental stages were both significant at 0.01 level, but the difference was not significant between two varieties. Shannon diversity indices indicated that the genetic diversity of rhizosphere soil microbes was lowest in rice and highest in lettuce. The rhizosphere soil microbes from 20 plant species could be clustered into three groups at the 0.454 (GD) level based on UPGMA, in which the first group was from rice, while the second group was from celery planted in plastic green house, and the third group was from 18 other plant species cultivated in dry lands. Our results suggest that SRAP is an efficient method for analyzing the genetic diversity in rhizosphere soil microbes.

Key words: rhizosphere soil microbe, SRAP, genetic diversity, genetic distance, cluster analysis