Root Nodules Of Leguminous Trees And Rhizobium Genetic Diversity

For many years, the research on N(nitrogen)-fixation of Leguminosae sp. has paticularly addressed on Legume crops, green manure and forage grass. Until the 1980's,the N-fixation of Leguminosae sp. began to draw wider attention and investigation on root nodules and germplasm collection of root nodule bacteria for woody Leguminosae plants were initialized.The root nodule bacteria penetrate into the Leguminosae plants to form symbiotic fixation. This paper mainly elaborated to study the morphological, structural and developmental characteristics of root nodule bacteria. Molecular markers were also employed to elucidate the genetic diversity and taxonomic system of root nodule bacteria from woody plants species.1. The outer morphology and structural changes at the different periods of growth of root nodules of Ribinia pseudoacacia were observed and it was found that the nucleus disappeared after the root nodule cells were infected with root nodule bacteria. The numbers of the meristem at the top are correlated to development of outer morphology of root nodules.2. The morphological and the structural characteristics of root nodules in 8 woody Leguminosae species were studied. It was found that root nodules varied in morphology, sizes and colors among the hosts. Their structure was similar to which had cortex, vascular bundle and bacteriocyte area. These root nodules could be divided into finite nodule and infinite nodule. The shape and size of nodules were correlated with nodule types.3. The polymorphophism of root nodule bacteria on 53 woody Leguminosae species were analyzed by PCR-RFLP. Clustering analysis revealed that the infected species were not correlated with the hosts and their area distribution. When compared with the previous studies, it was found that the morphology, properties of physiology and bio-chemistry and host resistance were somewhat correlated, but not identical, which implied that the same infected species being affected by evolutional and environmental factors, were sure to make corresponding changes in order to fit the environmental changes.4. Through 16SrDNA Sequence analysis on root nodules of infected woody Leguminosae species, their phylogenetic relationship was studied. Some conclusion were drawn based on the experimental data including the confirmation of taxonomic relationship of the most infected species, which provides the theoretical basis for the research on root nodule bacteria of woody Leguminosae species and lays the foundation on its development and rational utilization of the established root nodules germplasm.