Study On Biocontrol And Growth Promotion Effect And The Dose Of Microbiological Agent Nanjing Shield

In general, plant growth promoting rhizobacteria (PGPR) prevent plant diseases and promote the growth of the plant by one or more mechanisms. Under the pressure of plant diseases, PGPR can improve the disease resistance of plant, inhibit infection and expansion of pathogen through competition for nutrients, colonization site competition, inducing Systemic acquired resistance (SAR) and induced systemic resistance (ISR) or other methods. Under environmental pressure, some microorganisms can produce ACC deaminase, regulating ethylene content to cope with stress, promote the growth of the plant indirectly. However, some plant growth promoting rhizobacteria can directly promote the growth of plants in the absence of disease pressure. For instance, microorganisms may fix nitrogen, resolve phosphate or potassium, ultimately, providing plant with more nutrients. Or, they excrete plant hormones, such as auxin, cytokinin, gibberellin, to promote plant growth. Under normal circumstances, PGPR strains can take advantage of one or more of these mechanisms, but the exact mechanisms involved have not been very good interpretated. Growth-promoting effects of PGPR by some external factors or their influence, thus limiting the application of PGPR. Typically, PGPR within a certain range of doses showed better growth-promoting effect, and beyond the scope may exhibit a neutral or negative impact. Meanwhile, PGPR performance on different crops may also be different. In this study, biocontrol agents "Nanjing Shield" compounded by a variety of Bacillus subtilis. Past studies on biocontrol agents "Nanjing Shield" was focused on biocontrol of disease and capabilities of reliving stress. This study investigated the effects on seed germination, plant growth, yield and quality of a variety of leafy vegetables and Solanaceous and Cucurbitaceous vegetables under field conditions, as well as the optimal dose of Nanjing Shield applied in the field.1. Influence of Different Doses of Microbial Preparation "Nanjing Shield" on the Yield and Quality of leafy VegetablesIn this study, effects on growth-promoting, quality and chlorophyll on four kinds of leafy vegetables (spinach, lettuce, garland chrysanthemum, water spinach) was tested by seed germination and field experiment by setting up seven treatments with different doses (OL/hm2、3.0L/hm2、7.5L/hm2、15.0L/hm2、30.0L/hm2、75.0L/hm2) of "Nanjing Shield". The results showed that biocontrol agents "Nanjing Shield" can enhance germination rates of amaranth, lettuce, garland chrysanthemum, water spinach by 9.02%,12.22%,25.96%, 25.35% respectively. "Nanjing Shield" can significantly increase plant physiological indicators such as plant height, leaf number and leaf area, increasing yield by 32.62%-73.35% 45 days after harvest. In addition," Nanjing Shield" can significantly increase the soluble protein and soluble sugar content rather than Vc in leafy vegetables. By increasing chlorophyll a, chlorophyll b and total chlorophyll content in plant leaf, "Nanjing Shield" maintains plant’s strong capacity of photosynthetic and assimilation, thereby increases the yield and quality of leafy vegetables. According to the results of this study, combined with agricultural costs, the dose 15.0L/hm2 was suggested to be used.2. Influence of Different Doses of Microbial Preparation "Nanjing Shield" on the Yield and Quality of Solanaceous and Cucurbitaceous VegetablesField plot experiment were carried out on peppers, eggplants and cucumbers with different doses of microbial preparation "Nanjing shield" ("NS" for short), OL/hm2, 3.0L/hm2,7.5L/hm2,15.0L/hm2,30.0L/hm2 and 75.0L/hm2. Results show that crop heights, stem diameters, leaf numbers, leaf area and yields of all the "NS" treatments were increased in different degrees. Moreover, the optimal doses of "NS" for Solanaceous and Cucurbitaceous vegetables were 30.OL/hm2 and 15.OL/hm2. In addition, the contents of soluble sugar and soluble protein of "NS" treatments under these two doses was significantly higher than those of control, so NS can effectively improve quality of Solanaceous and Cucurbitaceous vegetables. According to the results of this study, combined with agricultural costs, the dose 15.0L/hm2 was suggested to be used. Correlation analysis displays that there were positive correlations between peppers, eggplants, cucumbers assignments and the yields, with a relationship index of 0.920,0.908 and 0.928, respectively. Thereby, an evaluation system was brought forward to screen the microbial agents of biofertilizers and their optimal dose. In order to further verify the actual effect of the dose, field experiments were carried out on peppers, eggplants and cucumbers in Jiangsu Taizhou Huangqiao Park and Huai’an. Ultimately, field application of the selected dose effectively controlled Phytophthora Blight of peppers, Verticillium Wilt of Eggplants; cucumber root knot nematode of cucumbers, achieved more than 60% of the biocontrol efficacy and more than 20% of the production increase.