The Relations Between Nutritional Metabolisms And Resistance Of Pinus Armandi To Dendroctonus Armandi And Symbiotic Fungus

Dendroctonus armandi (Coleoptera: Scolytidae) is the most notorious phloem bark beetle species in pine ecosystem of Qinling and Bashan mountains, it has the Seriously damaged with the symbiotic fungus to the healthy Pinus armandi, which causes the host trees massive deaths, resulted the enormous economy loss in the outbreak areas. Therefore, up to now the most researches focused on the differences of nutrient and enzyme activities, resistance of phloem in P. armandi while attacked and infected by D. armandi and its symbiotic fungus, and the biology characteristic of Leptographium qinglingensis, and so on, for that displays the role of D. armandi and its symbiotic fungus in the decomposition and transformation of nutrient of the host trees, the dependences of overcoming the resistance system of host trees and nutrition utilized, and the conditions, such as temperature, humidity, pH value etc., for mycelia growth and spore development of symbiotic fungus. The results are as follows.At the beginning of the attacked by Chinesis white pine beetle (D. armandi) and their symbiotic blue stain fungus (L. qinlingensis), PAL, PPO, SOD activities and MDA content significantly increased in the phloem of P. armandi, then decreased with the increase of the number of D. armandi and the infecting blue-stain fungus to the xylem and phloem of P. armandi, and reached the minimum level in withering stage of P. armandi. But the contents of nutrition materials in the phloem, such as water, protein, glucide, fat, and amylum and so on, declined with the infestation of D. armandi and symbiotic fungus.With the rapidly infecting and expanding of L. qinglingensis in xylem and phloem of infected P. armandi sapling, the content of chlorophyll of pine needle is reduced remarkably. The content of water, soluble sugars and protein, the activities SOD and CAT in reaction zone of phloem was lower in infected tree than those in healthy ones, but the content of MDA in which was higher. It was very apparent that the more fungi be inoculated, the lower the content of water, soluble sugars and protein, etc in host tree. The results showed that, the enzyme activities and the content of nutrient were significantly decreased by infected with L. qinglingensi, which weaken the resistance of host gradually and accelerated nutrients transformation in tissue of P. armandi, and created nutritional conditions for survival of D. armandi in phloem. L. qinglingensis is the pathogenic fungus carried with D. armandi, which develops in the tissues and cells of xylem and phloem of P. armandi after D. armandi attacked host trees, decomposes the resinosis cell and the parenchyma cell in resin canal, then affects the metabolism of resin and the moisture content. The growth of fungus is influenced significantly by temperature, pH value, medium, and water potential. The suitable temperature for mycelia growth is 20~30℃, and the optimum is 27.5℃.The optimum temperature for spores germination is 20℃; The suitable pH value for mycelia growth is 4.0~6.5 and the optimum pH value is 5.0; The optimum medium of mycelia growth and spore numbers is malt-agar medium; The mycelia are used to grow in higher water potential, the mycelium biomass reduces as the water potential decreases; In four tested PDA medium with different extract of pine needle, the optimum medium is the one with needle nutrition of P. armandi. Furthermore, the statistic results show that in the six tested fungicides possess certain antifungal activities against L. qinglingensis, the suitable fungicide is zineb, topsin-methyl, metalaxyl, cupric oxide.The research not only shows the harm mechanism of D. armandi and its symbiotic fungus to the host from the physiological and biochemistry angle, provides the important theory basis to further clarify the mechanism of bark beetles and symbitic fungus for nutrient utilization of host trees, but also studies on the artificial feed to raise the bark beetles exploration and the biology characteristic of L. qinglingensis, and antifungal activities of fungicides, which has important practice significance on exploring the new mentality and the new method for exploring the bark beetles sustainable control.