Study On Tuberculina Elaeagni, Mycoparasite Of Elaeagnus Umbellate Rust

Elaeagnus umbellate is a valuable wild plant and the rust caused by Aecidium elaeagni-umbellatae Diet. is one of the most important diseases in Elaeagnus umbellate. The occurrence of Elaeagnus umbellate rust resulted in leaf blight and casting, weakenning the tree power seriously. Long-termed chemical control method caused "3R" that were Resistance, Resurgence and Residue. As the important natural mycoparasite of Elaeagnus umbellate rust, Tuberculina elaeagni Y. Huang et Z. Y. Zhang would have potential value in exploitation and application. In this paper, cultural characters, biological characteristics, infection cycle and parasitical specialization were primarily studied so as to provide significant theoretical foundation for the use of T. elaeagni as a potential biocontrol agent of Elaeagnus umbellate rust.When T. elaeagni was cultured on Potato dextrose agar medium at 25℃, white colony appeared after 4~5 days, the hypha had septa and branches and constriction at the site of branches. An averaged diameter of hypha was 3.25μm. After 7~8 days, conidia began to form and exhibited achromatous. As conidia produced and the number increased, colony began to be caelate gradually and didn't expand basically. Finally it formed circular or circular-like brown conidia stack.The effect of culture media, carbon and nitrogen sources, temperature, pH and illumination on the mycelial growth, sporulation and conidial germination of T. elaeagni was primarily studied, results showed as followings:Ten media were used in this experiment and the result showed that T. elaeagni grew best on the medium(potato 200g, glucose 20g, active carbon 1g, agar 20g, distilled water 1000ml) and air-dried weight of the mycelia reached the maximum. For the sporulation of T. elaeagni, the medium(potato 200g, glucose 20g, peptone 2g, agar 20g, distilled water 1000ml) was so desirable that the number of conidia was more than that of the others significantly. A little mycelia appeared and no conidiaproduced on the Czapek medium, and the Water agar medium was the worst for the mycelial growth and sporulation.Carbon source had significant effect on the mycelial growth and sporulation of T. elaeagni. Air-dried weight of the mycelia and the number of the conidia basically exhibited positive correlation. It was namely that carbon source benefited mycelial growth was the same what got the greatest amount of the conidia. Among five carbon source used, glucose was the best for the mycelial growth and sporulation, And the second was maltose and soluble amylum, while check was the worst, which showed that carbon source was necessary for sporulation. For the use of nitrogen source, T. elaeagni could grow better on ammonium sulfate, potassium nitrate and ammonium chloride, among which ammonium sulfate was the best and sodium nitrate was the worst. As for conidial formation, peptone was the most favorable and ammonium sulfate was the worst. Check was much better than that of beef extract. The result indicated that suitable nitrogen source could improve conidia formation, yet the excessive had a certain inhibition.For the mycelial growth and sporulation of T. elaeagni, the range of temperature was 15~30°C, the optimum being 25~28°C and 25°C for its growth and sporulation, respectively. The optimum of pH was 6. Fluorescence had no significant effect on mycelial growth, but it could stimulate sporulation. The following optimal sporulation conditions were similar to the national report ofT.pyrus.Temperature and humidity were important factors for conidial germination, the optimum was 25°C and the germination percentage was 89.2%. At this temperature, it couldn't germinate until six hours. When relative humidity reached above 65%, conidia could germinate. In free water, the percentage of conidial germination was highest and it was 80.4%. The optimum of pH was at the range of 5~6 and illumination was good for conidial germination. Its lethal temperature was 43°C(10min).It showed that T. elaeagni overwintered at the parasitized rust branches and leaves collected in field for second source of infection. The conidia were disseminated by airflow. The germ tube of the conidia penetrated through ostioles of the spermagonia. Incubation period of the mycoparasite was closely correlated with temperature. At the temperature of 20°C and 25°C, the incubation periods were 9d and 7d, respectively.By the cross inoculation with six different mycoparasites that were T. pyrus, T.fraxinis, T. elaeagni, T. persicina, T. sambuci and T. schisandrae on the spermagonia of pear rust, Fraxinus chinensis van rhynchophylla rust, Elaeagnus umbellate rust, Schisandra sphenanthera rust and Sambucus williamsii rust, mycoparasitism could not be observed. The result showed that the six mycoparasites hadparasitical specialization. As for T. elaebgni, it namely was that T. elaeagni could parasitize the aecia of Elaeagnus umbellate rust, but it couldn't parasitize the aecia of pear rust, Fraxinus chinensis var. rhynchophylla rust, Schisandra sphenanthera rust et al, the reverse was the same.