Research On Extension Of Storage Life For Oil Formulation Of Beauveria Bassiana

On the foundation of the research by the Research Center for Entomogenous Fungi of Anhui Agricultural University, the thesis tries to make a further study on extending the storage life of Beauveria Bassiana oil preparation. Mainly from the aspects of the preparation and storing of high grade conidia of Beauveria Bassiana, the corresponding treatments for oil preparation, and the compatibility testing between oil preparation and pesticides, the thesis attempts to find some new ways to extend the storage life of Beauveria Bassiana oil preparation at normal temperature. The main researching ways and the results of the experiments are as follows:1. From the angle of the nutrition condition requested by Beauveria Bassiana, three different supplementary carbon and nitrogen sources are added to the conidial culture medium in Beauveria Bassiana, the experiment has raised three kind of strains (Bb13, Bb380, Bb202) and produced conidial powder, at the same time, the conidial content, percentage of conidial germination, and water content are examined. Through analysis and comparison, sucrose and glucose, the best carbon sources, and potassium nitrate and peptone, the best nitrogen sources have been screened and added to the conidial culture medium in Beauveria Bassiana which has high output, high quality, strong vigor and low water content. Moreover, different strains of Beauveria Bassiana have different endurance capacity to high temperature, undernourishment, etc. in disadvantageous environment, this experiment has tested conidial quality of strains of the three different hosts, and has discovered that the conidial quality produced by Bb13 obviously surpasses the other two strains.2. After screening carbon and nitrogen sources, synthetically considering the nutrition demand and the raising condition in the process of preparation of the conidial powder of Beauveria Bassiana, the orthogonal experiments are conducted under the different raising temperature, the pH value and the culture medium with different supplementary carbon and nitrogen sources and microelements. Taking conidial content and percentage of conidial germination as the main index, glucose, the best carbon source, and peptone, the best nitrogen source, are screened for the growth of Bb13, the microelements, copper and zinc, can greatly promote the production and germination of conidia, the most suitable pH value is 6～7, and the most suitable raising temperature is 20～25℃.3. In the course of storing conidial powder, temperature and water content are important factors to affect the storage life of conidia. At 4℃and 25℃, five kinds of water contents of conidial viability are tested for 18 months, the result shows, at 4℃, conidia treated by 1.25～9.87% water content can be stored for 18 months, conidial viability can be kept over 90%, treated by high water content(13.89%), the conidial viability of conidial powder slowly drops from 97.38% to 77.94% in the first 9 months, after that, the conidial viability will accelerate the speed, 420 days later, all the conidia will die out, which indicates that conidia power with high water content should be stored in cold places within 7 months (conidial viability at that time is 84.11%); at 25℃, conidia treated by 13.89% water content have completely deactivated when examined on the 30th day( No germinated conidia can be found); deactivation of all conidia treated by 9.87%, 7.36% and 4.28% water content occurs separately on the 195th day, 225th day and 420th day; treated by the lowest water content(1.25%), the conidial viability drops much slowly than that by high water content, after 18 months, the conidial viability will keep up (15.94±1.26)%. Therefore, to store conidia at normal temperature, the water content must be controlled below 5% so that conidia can be stored for about 5 months and the conidial viability can be kept over 80%.4. By controlling nutrition and bathing at high temperature, the conidia of Beauveria Bassiana have been confected into oil formulation, the conidial viability of oil formulation of conidia under controlled nutrition is compared with the controlled group, the remarkable difference exists in both. In the course of storage of oil formulation of the optimized culture medium, the conidial viability is gradually dropping down with time going on, but its tested value is always higher than the conidial viability of oil formulation when its nutrition is controlled at the same time. But from the 120th day on, the conidial viability of oil formulation (38.3%) with carbon controlled is obviously getting lower than the conidial viability of oil formulation (40.3%) with nitrogen controlled, afterwards it continuously low and there is obvious difference between them, on the 240th day, the conidial viability of oil formulation with carbon controlled falls to 0, but the conidial viability of oil formulation with nitrogen controlled still maintains at 5.64% when it is stored on the 330th day. From this it is concluded that the storage life of Beauveria Bassiana oil formulation with nitrogen controlled is longer than that with carbon controlled.After bathing 50℃, conidia are confected into oil formulation, 270 days before storing, the conidial viability in oil formulation is always lower than the controlled group, the difference among them is obvious, moreover, the longer the bathing time is, the lower the conidial viability is. But the conidial viability of bathed conidia in the oil formulation drops more slowly than that of the controlled group, however 300 days later, the conidial viability of bathed conidia in the oil formulation gradually becomes higher than that of the controlled one, there exists great difference among them, therefore, it is concluded that conidia of Beauveria Bassiana can be properly treated by high temperature, which will help to improve the conidial viability in oil formulation late in its storage. Furthermore, the conidial viability of conidia bathed for 30 minutes and conidia bathed for 60 minutes in oil formulation have great difference after storing for 300 days, according to this, if the bathing time is properly prolonged, the conidial viability in oil formulation will be lengthened to certain degree in mid and late periods of its storage.5. If extra nutrition is added to the oil formulation of Beauveria Bassiana at different period of time, the percentage of conidial germination will be improved compared with the controlled group, also there exists great difference compared with the controlled group (percentage of conidial germination is 5.42%). Moreover the extra nutrition added to the oil formulation separately in the first three months is more effective than that in the last three months, there exists great difference among them, especially in the third month, when extra nutrition is added to the oil formulation, the percentage of conidial viability will arrive at 8.41%, which is much higher than that of the controlled group, the percentage of conidial germination of conidia with extra nutrition in the oil formulation after the third month respectively is 6.03%, 5.59%, 5.74%. Therefore, to add extra nutrition to the oil formulation of Beauveria Bassiana stored at normal temperature at the right moment is an effective way to recover vigor of conidia and improve the percentage of conidial viability of oil formulation.6. The compatibility between Beauveria Bassiana and salad oil, paraffin oil is excellent, through thermal test, the change of processing temperature and the length of processing time take effect on the percentage of conidial germination and viability of conidia of Beauveria Bassiana for different formulations. With the processing temperature raising and the processing time lengthening, the percentage of conidial germination of conidia in the water formulation and paraffin oil formulation drops with it; which takes no effect on the viability of conidia in salad oil formulation except for its speed of over 90% conidial germination being delayed(approximately 3h) compared with the controlled group. Therefore, salad oil may be used as the best carrier for oil formulation of Beauveria Bassiana.7. Compatibility test between Beauveria Bassiana and ten kind of pesticides: The size order of compatibility from large to small is: Bt(bacillus thuringiensis) > Deltamethrin > DCP-V(dendrdimus cytophasmic polyhedrosis virus) > Imidacloprid > Triazophos > Bisultap > Omethoate > Abamectin > Flufenoxuron > Chlorfluazuron.As for different concentrations of the same pesticide, the effect that pesticide takes on the percentage of conidial germination of Beauveria Bassiana is closely related to its concentration, moreover, the percentage of conidial germination of Beauveria Bassiana under normal concentration(1.0×) is lower than that under diluted concentration (0.1×, 0.2×). The percentage of conidial germination has no obvious difference among the normally used concentration dilutes in 5 times of and 10 times of 8000IU Bt WP, 2.5% Deltamethrin EC, DCP-V WP, 10% Imidacloprid WP, 10 times of 2% Triazophos EC, and 5 times of 18% Bisultap compared with the controlled group, they may be combined with oil formulation of Beauveria Bassiana and work with each other to function better.