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Twelve representative soil samples were collected from different altitudes on the northern slope of Taibai Mountain to study the distribution and characteristics of soil antagonistic actinomyces by using agar block method. There existed a great deal of soil antagonistic actinomyces in the study area. Among the 141 actinomycete strains isolated,116 strains (82.3%) showed antagonism toward 12 target bacteria or fungi.The antagonistic strains at altitudes 800-1845, 3488,3655, and 3670 m occupied 73.7%-86.8%,81.3%, 78.9% and 82.3% of the total, respectively. 42.1% of the strains at altitudes 1200-2300 m and >3400 m showed strong and broad spectrum antagonistic activity, suggesting that there was a great potential for the isolation of actinomycete strains with strong anti-biotic capability at these altitudes. 24.1% of the antagonistic actinomycetes showed antagonism against Staphyloccocus aureu, and 2.4%, 6.9% and 11.2% of them showed activity toward Verticillium dahliae in cotton,Phytophthora sp. in strawberry and Neonectria radiciccla in ginseng, respectively. This study showed that the soil actinomycete antagonistic potentiality (SAAP) could be used as a quantitative indicator to evaluate the potential of antagonistic actinomycete resources in soil. [ABSTRACT FROM AUTHOR]

Bacillus laterosporus Bl13 has good antagonistic effect on the pathogen of tomato early blight (TEB) disease. A pot experiment was conducted to investigate the effect and mechanism of B. laterosporus Bl13 against TEB disease by measuring biological traits such as plant height, stem diameter, disease index of TEB, activity of plant defense enzyme in leaves, and microbial diversity and community composition in root area. The results showed that B. laterosporus Bl13 could significantly reduce the disease index of TEB disease incidence, increase the activity of defensive enzymes including polyphenol oxidase (PPO) and peroxidase (POD) in leaves, and reduce the effects of the disease on the aboveground and root growth of tomato. Meanwhile, B. laterosporus Bl13 improved soil microbial community structure in the root zone, by significantly increasing the relative abundance of plant growth-promoting bacteria ( Bacillus and Pseudomonas ) and decreasing that of Olpidium and Haematonectria . The results showed that B. laterosporus Bl13 could enhance plant resistance against TEB disease through improving the activity of defensive enzymes in tomato leaves and increasing the number of beneficial microbes in the root zone.

The effects of Bacillus Bs10, Ba12 and Bl10 on tomato growth and soil rhizosphere microorganisms were determined by Petri dish germination test and pot experiments. The results showed that Bs10, Ba12 and Bl10 exhibited remarkable promoting effect on the length of hypocotyl and radical, as well as the growth of plants. The length, surface area and volume of tomato roots increased significantly after treatment with Bacillus stains, the numbers and proportions of soil bacteria also increased markedly, while those of soil fungi decreased. The numbers of the dominant bacteria and fungi were changed, withBacillus methylotrophicus being much higher in root zone soil, surface soil and neouchi, while the plant pathogens Fusarium solani and Fusarium oxysporum decreased significantly in root zone soil and root surface soil. These results suggested that the addition of Bs10, Ba12 and Bl10 could improve the micro-ecosystem of the root domain of tomato, which might play an important role in growth promoting and disease prevention on tomato plants.

This paper was mainly to explore the effects of two Streptomyces strains (S. roche D74 and S. pactum Act12) and their mixed actinomycetes agent on maize growth. Petri dish germination test, sand culture trial and plot trial were performed to determine the biological properties, leaf inducible enzyme activities, photosynthesis, ear characteristics, grain yield and quality of maize after seed soaking with acellular culture filtrate of D74 or Act 12 and seed coating with the mixed actinomycetes agent of two Streptomyces stains. The result showed that the seed soaking treatment significantly contributed to hypocotyls, radical and seedling growth, and increased the leaf inducible enzyme activities of maize seedlings. The 1000-fold dilution of D74 improved hypocotyl length, radicle length, and fibrous root number by 43.4%, 26.4%, and 100.7% (P<0.05), respectively, whereas the undiluted solution of D74 improved leaf polyphenol oxidase (PPO) activity by 40.2% (P<0.05). The 1000-fold dilution of Act12 improved hypocotyl length, radicle length, and fibrous root number by 36.3%, 36.3%, and 117.5% (P<0.05), the total fresh mass and root fresh mass by 31.1% and 36.6%, respectively (P<0.05). The 10-fold and 1000-fold dilutions of Act12 improved leaf PPO activity by 38.1% and 39.5%, respectively (P<0.05). The seed coating treatment showed the following significant effects, compared with the control: 1) Improving the root development. 2) Enhancing the leaf photosynthesis. 3) Improving the ear characteristics and grain yield. 4) Promoteing the grain filling. 5) Improving the leaf inducible enzyme activities. The results indicated that seed coating with the mixed actinomycetes agent of two Streptomyces strains could significantly affect the biological characteristics, photosynthesis and biochemical metabolism of maize seedlings, stimulate root development, promote plant growth, and improve grain yield of maize.

Twelve representative soil samples were collected from different altitudes on the northern slope of Taibai Mountain to study the distribution and characteristics of soil antagonistic actinomyces by using agar block method. There existed a great deal of soil antagonistic actinomyces in the study area. Among the 141 actinomycete strains isolated, 116 strains (82.3%) showed antagonism toward 12 target bacteria or fungi. The antagonistic strains at altitudes 800-1845, 3488, 3655, and 3670 m occupied 73.7% -86.8%, 81.3%, 78.9% and 82.3% of the total, respectively. 42.1% of the strains at altitudes 1200-2300 m and > 3400 m showed strong and broad spectrum antagonistic activity, suggesting that there was a great potential for the isolation of actinomycete strains with strong anti-biotic capability at these altitudes. 24.1% of the antagonistic actinomycetes showed antagonism against Staphyloccocus aureu, and 2.4%, 6.9% and 11.2% of them showed activity toward Verticillium dahliae in cotton, Phytophthora sp. in strawberry and Neonectria radiciccla in ginseng, respectively. This study showed that the soil actinomycete antagonistic potentiality (SAAP) could be used as a quantitative indicator to evaluate the potential of antagonistic actinomycete resources in soil.

Sanjiangyuan region (the headstream of three rivers) in Qinghai Province of China is the highest and largest inland alpine wetland in the world. The study on the nutrient contents and microbial populations of aeolian sandy soils in this region showed that soil organic matter content increased with the evolution of aeolian sand dunes from un-stabilized to stabilized state, being 5.9 and 3.8 times higher in stabilized sand dune than in mobile and semi-stabilized sand dunes, respectively. Soil nitrogen and phosphorus contents increased in line with the amount of organic matter, while potassium content and pH value varied slightly. The microbial populations changed markedly with the development of vegetation, fixing of mobile sand, and increase of soil nutrients. The quantities of soil bacteria, fungi and actinomycetes were 4.0 and 2.8 times, 19.6 and 6.3 times, and 12.4 and 2.6 times higher in stabilized and semi-stabilized sand dunes than in mobile sand dune, respectively, indicating that soil microbial bio-diversity was increased with the evolution of aeolian sand dunes from mobile to stabilized state. In addition, the quantities of soil microbes were closely correlated with the contents of soil organic matter, total nitrogen, and available nitrogen and phosphorus, but not correlated with soil total phosphorus, total and available potassium, or pH value.