Persistence Of Temporal And Spatial Dynamics Of Metarhizium Anisopliae In Soil

Metarhizium anisopliae is an important entomopathogenic fungus in control of agriculture and forestry pest control. Few results of survival status of M. anisopliae applied in the field were reported. This dissertation studies aim to clarify the temporal and spatial dynamics of the fungal persistence in soil after application. The experiment was carried out in Cangzhou, Hebei province. The results are as follows.Firstly, a optimized selective medium adding dodine was obtained,for isolation of M. anisopliae from soil. Its constituent included sucrose 20g, yeast extract 10g, agar powder 20g, dodine 50mg and chloromycetin 200mg/L in 1000mL. Non-target microbials could be completely inhibited and the highest separation efficiency could reach 72.4% at 5mg/100ml of dodine in the medium.In uniform treatment plot with M. anisopliae, the quantity of the fungus CFU (colony forming unit) from the soil showed different trends in different relative positions of the peanut plants. The quantity of the upper layer of 3cm depth, including the three distances that 12.5cm, 25cm and 37.5cm from the plant, showed similar trend. The CFUs all decreased rapidly to 73.6%,70.7% and 52.4% in the first 30d after treatment, and to 28.4%,24.7% and 26.1% at 60th d. The CFUs reached about 20% at 90th d and then showed slow rise. The CFUs reached 58.4%,34.4% and 33.2% at 150th d. The quantity of the fungus CFU from soil at 15cm depth, including the three distances that 12.5cm, 25cm and 37.5cm from the plant, showed the trend of going down rapidly below 50% at the 60th d. After going through a steady period and a certain extent decline period during the peanut ripe (120th ~150th d), and the CFU from soil decreased to a very low level, that was close to the untreated soil. The quantity of the untreated soil at the lowest layer at 30cm depth and below the root zone remained at a relatively low level. There was no significant difference compared with control soil. In the root rhizosphere and root surrounding, the quantity of the fungus decreased firstly, and then increased with time getting along. There were significant differences of CFUs tested between different sampling time. The CFU at the root rhizosphere decreased to 19.3% of control soil, then went through a steady period and than rise again to 76.0% at last. The CFUs at the root surrounding decreased to the lowest level, 23.6% of control soil, and returned to 48.3% at 150th d. From the analysis of spatial variation, it is found that CFU beyond decrease faster than one's near among the three distances that 12.5cm, 25cm and 37.5cm from the plants, with significant differences. In the depth of 3cm and 15cm from the three distances, the trend of the CFU decrease is similar in the 90d, to about 20%. The former would shift to rise faster at 12.5cm,but CFUs at 15cm would continue decrease slowly. The CFUs at the root surrounding area and the root rhizosphere rally fast, and CFUs at the root rhizosphere rally faster, with significant differences.Two non-uniformly distributed treatments,one was fungal application only outside the baskets and another was only inside the baskets, were set for investigation of the fungal growing direction. The results of fungal application outside the baskets showed that the fungal quantity at the upper, middle and lower soil samples inboard baskets went up at initial stage and then fluctuated in a narrow range along with the peanut plants growth. At 30th day, in all layers of the soil, the fungal CFUs increased to different value. The biggest reached 7.4 times as the control, appeared at the upper layer. CFU at the root rhizosphere changed unobviously at 30th d, but climbed slowly to 600 at 60th d and went on. During the 90th~120th d, it increased more rapidly, up to 2820 CFUs, being 10.8 times as the control. By the treatment of fungal application inside the baskets, it showed that the CFU trend at the upper, middle and lower soil samples outboard baskets had no significant differences. It went up at 60th d and the number ranged in 110~450. Then it fluctuated in a narrow range and reached the top 750 at upper layer at 150th d. The quantity of the upper, middle and lower soil inboard baskets showed general downward trend and fluctuation at long intervals during 150d. At last, the CFUs of the various layers tended to the same. So the conclusion was that there was a trend of M. anisopliae growed from the fungal applied area to that without the fungus at the basket boundary of 12cm away from the plants, but it had no postive or negative to roots. At the root rhizosphere of peanut, the fungus showed the positive taxis and the adaptability along with the root growth.