And From Plant Rhizosphere Bacteria In Cowpea Seedling Raising And Application Research Of Rice Seedlings

In order to meet the increasing demand for food, fruit, vegetable and other agricultural products for consumers, many agriculrural farmers have increased the input of fertilizer, pesticide, hormones and other agricultural chemicals. The long-term uses and abuses of agricultural chemicals give rise to environmental disruption and food security issues, such as deterioration of soil structure, water pollution, pest increase, pesticide residue and so on. Therefore, questions as to how to enssure the grain yield and quality with low input rate of agricultural chemicals remain unanswered and is challenging scientific community. Improved cultural practice is one of the approaches. In addition, agricultural biological agents are now attracted more and more attention as their benifical and environmentally friendly effecs.Microbial manure refers to a specific class of products containing living micro-organisms. It has been used in agricultural production to improve available nitrogen in soil, increase the effective phosphorus in soil, and provide hormone for plant growth. Living microbial plays a key role in this effect.Plant growth promoting rhizobacteria (PGPR) are usually the source of agents in microbial manure. These bacteria colonize the rhizosphere of many plant species and confer beneficial effects. PGPR can promote plant growth directly by producing some substrates which plants need or help the plants uptake nutrients from the environment. PGPR also reduce or prevent the impact of adverse environment (such as pathogens, heavy metals, etc.) on plant growth, thereby indirectly promote plant growth.However, the good results obtained in vitro cannot always be reproduced under field conditions. The inconsistency in the performance of PGPR may be due to its poor environmental adaptation ability and low competitiveness against pathogens or native soil microorganisms, which becomes a vital issue in PGPR application. Thus, screening for PGPR strains with high plant-specific and soil-specific effectiveness is becoming the vital process for agricultural biological agent commercilizatopn. Present work tried to apply isolated PGPR strains for cowpea and rice seedlings, in order to provide bacterial strains for agricultural biofertilizer development. The results showed as follows:(1) RA6and WP8both exerted promoting effect on growth of cowpea seedlings. In the meantime, the effects of PGPRs on cowpea growth were different because of different inoculation methods and inoculum rates. Seeds soking did better than soil drench method. WP8used as seed-soking agent and RA6used at high inoculum rate both increased germination rate by14.29%(P<0.05). WP8and RA6used as seed-soking agents increased plant height by14.39%and10.40%(P<0.05). Significant differences were found between treatments and control. However when inoculation rate was increased to10cfu/g soil, above-ground dry weight was increased by27.37%and20.43%(P<0.05) respectively, significantly higher than that of control. Application of WP8and RA6both shaped the structure of indigenous bacterial community to some extent.(2) Three PGPRs, especially Pseudomonas sp. RBP1å'ŒBacillus sp. WP8, could significantly improve seedling quality. Using the strains as soil drench conbined with "ZYJ", seedling heights were significantly shorter and stems were significantly thicker than that of control. Without adding "ZYJ", strain inoculations brought about an increase in above-ground dry weight, as compared with those of control. Inoculation of WP8(soil drench) and RBP1(seeds soking) increased the above-ground biomass by28.39%and34.57%(P<0.05), respectively. Soil drench was more efficient than seed soaking. The above-ground dry biomass was more sensitive than other indexes in assessing the effects of inoculation. Three PGPRs caused moderate changes of community structure of indigenous bacterial community, implying that using RBP1and WP8is an eco-friendly approach to rice production.