Abstract:

An investigation was conducted on rhizobial resources of Trifolium repens in the central region, northeastern area, southern part, southwestern area and northern region of Guizhou Province, in which a total number of 73 root nodule samples were collected. Of all the samples, a majority of the root nodules were distributed on lateral root or fibrous root, just a minority growed at tap root, and most of them were shaped as palmate, cylindrical and spherical, a few were shaped as sector and petal, more specific nodules were shaped as flower. Many root nodules presented three colours, white, pink and green, or two colours, pink and green, arranged in a column, some with other arrayed colours, and the average diameter of nodules was from 0.5 to 3.0mm, suggesting the morphological characteristics of root nodules of wild white clover show high levels of polymorphism and it has a close relationship with the geographical environments. A total of 107 rhizobium strains were obtained by means of isolating from collected samples, purifying and identification of gram staining. Then the 16S rDNA sequences of all the preserved strains were aligned, their floristic characteristics were analysed, and the results showed that the 107 rhizobium strains were dispersed over 6 genera, 20 species, among them the distribution frequency of Rhizobium amounted to 81.31%, which was the predominant genus in all the investigation areas. In addition, the distribution frequencies of other five genera were from 5.61% to 0.93%. In all of the 20 species, the species with higher occurrence frequency were Rhizobium. leguminosarum, R.anhuiense and R.laguerreae, whose occurrence frequencies were 38.32%, 24.30% and 9.34%, respectively, and the occurrence frequencies of other 17 species were only from 4.67% to 0.93%. This investigation provided valuable germplasm resources for rhizobia utilization in regional agricultural and livestock production and ecological environment construction.

Key words: Wild white clover, Rhizobia, Resources survey, Floristic analysis