Studies On Acacia Spp. Rhizobia

In this study , root nodules were selected from 7 kinds of Acacia spp. forests in various site conditions and 53 strains rhizobia were isolated and purified, and then rather complete and systematic research . The colony have typical rhizobia colony features on plate cultivation. When inoculating or cross-inoculating in test tubes and potted seedlings ,the nodules could appeare in its host plant and had nitrogenase activity . There were positive reaction about use of citrate, and negative reaction about use of 3-ketolactose, beef extract peptone, hydrolysis of starch in all test strains and liquefaction of gelatin in greater part of strains. (NH4)2HPO4 was used in all test strains and KNO3 was used in most of them as nitrogen sources. Both five monosaccharides and three disaccharides could be utilized as carbon sources except HM11 which is unable to use lactose . Some strains generate acids and other generate alkali in BTB tests and so litmus milk reactions.Acacia spp. rhizobia have wider rang of adaption for growth environment. Among the 53 strains for the tests, some strains could grow between 9~39癈. Some strains could grow on pH 4.0 -9.0 cultrue medium, while some nodule bacteria of the Acacia spp. can adapt slightly sour (pH 4.0) or alkaline (pH 9.0) growth environment conditions. Some strains could grow quite well in NaCl solution concentration 0.2% to 2.0%. 2 strains having no resistance to all the antibiotics used in the tests and 4 strains having resistance to all the antibiotics, other nodule bacteria of different Acacia spp. have obvious differences in resistance to antibiotics .After generation time determination and tests of colony formation days on plate for the 53 separated and purified strains of nodule bacteria from Acacia spp. species, fast-growers and slow-growers rhizobia came for the first time from nodule bacteria of the Acacia spp, 9 belonging to slow-growers rhizobia (generation time above 6.2 h) including 4 with growth generation time beyond 10 h. The results showed that the slow-growers rhizobia isolated from Acacia spp. with superior tolerance to stresses of acid, alkali, temperature and NaCl as many fast-growers rhizobia.The results of Acacia spp. seedlings inoculated or cross-inoculated with 53 strains Acacia spp. rhizobia in test tubes showed that average nodulation rate was 53.5%, nodulation amounts of single seedling was 2.4 , nodule weight of single seedling was 6.4mg , single nodule weight was 2.7mg , nitrogenase activity was 2126 nmol C2H4 g-1 h-1. The nodule could not appeare in its host seedlings without rhizobia in test tubes.When potted Acacia seedlings were inoculated with 33 strains of rhizobia separted and purified from the nodules of different Acacia spp, the average nodulation rate, nodulation amounts of single seedling, nodule weight of single seedling ,single nodule weight, seedling height growth, basal-diameter growth, total biomass of single seedling, nitrogenase activity , nitrogen contents in the leaves and total nitrogen fixationof single seedling separately increased by 6.2%, 142.1%, 113.9% , 48.6%,27.4%, 14.4%, 26.5%,40.5% ,20.8% and 51.4% over the control group .The results of afforestation by inoculation with nodule bacteria has indicated that ZG04 has best integrated effects, with tree height growth increasing by 15.5%, basal-diameter growth by 7.5% and chlorophyll contents by 10.3% ranking first among all the stains. After 5 strains of nodule bacteria of different Acacia spp. species were inoculated into Acacia crassccarp seedlings.For the first time, determination and analysis were made on 16S rDNA sequencing of nodule bacteria of bean trees by method of molecular biology. The results of determination and analysis on 16S rDNA sequencing of HJ06 showed that it has 98% isogenesis in nucleotide levels with Rhizobium tropici Rhizobium rhizogeness Rhizobium genosp and Rhizobium leguminosarum\6S rDNA, thus it with these species should belong to the same genus.For the first time, nifA gene segments was generated from nodule bacteria of bean trees species by PCR metho...