Study On Biological Characters And Control Of Blue-Stain Fungi Of Sapwood

Bluestain fungi cause a reduction in the timber utilization by discoloring sapwood, decreasing the aesthetic quality of wood. Thereby, it is an important research work to prevent discoloring of sapwood in period of wood using. In this dissertation, 5 types of staining strain were isolated and identified from blue-stained Pinus massoniana, Pinus sylvestris var.mongolica, and Hevea brasiliensis. The cultural characteristics and biological characteristics and their chemical and biological control were investigated. The results and described as follows:1. Fungiali isolation and identification. Five types of staining strain were isolated from blue-stained Pinus massoniana, Pinus sylvestris var.mongolica, and Hevea brasiliensis by conventional isolation and purification method. These fungi are identified as Botrydiplodia theobromae Pat., Fusarium verf/cz7//0/fife.st(Sacc.)Nireberg, Trichoderma harzianum Rifai, Trichoderma viride Pers.ex Fr., Penicillium purpurogenum Stoll, respectively. They all fall into the category of Deuterornycotina.2. The cultural characteristics of the staining fungi. Five types of staining fungi were inoculated, and cultured on the culture medium of PDA Petri dishes. The cultural characteristics of five staining fungi were evaluated according to their individual characteristics, such as colony morphology, colony color, variation of medium color, conidial fructification morphology, conidia form. The cultural characteristics of staining fungi take on uniform growth characteristics in natural conditions, which can be classified and identified according to their cultural characteristics.3. The influence of nutritional factors on the staining fungi. Employing Czapack's medium as the fundamental medium, different carbon sources and nitrogen sources were selected to culture staining fungi, and their growth characteristics were observed. Theresults showed, for 11 types of carbon sources, the five staining fungi didn't grow on the medium of crystalline cellulose, sterols, and carbon-absent medium at all. However, they grew weakly on the medium of glycerol and vigorously on the medium of soluble sugars. 8 types of nitrogen sources were able to be decomposed and assimilated, to a wide range of extent, by the five staining fungi. There were no obvious differences in their preference for organic or inorganic nitrogen. They didn't grow on nitrogen-absent medium at all.Only variation in certain color occurred for the culture medium, which resulted from the staining fungi's growth on the medium containing different carbon sources. There's no different color involved. While as for nitrogen sources, the same staining fungi may result in different color pigment on the medium containing different nitrogen sources. This was the case especially for Fusarium verticillioides(Sacc.)Nirebergi which tended to form pigments of different color, nearly on each type of medium containing different nitrogen sources. Therefore, different carbon sources determined whether staining fungi pigments were formed or not, yet didn't influence the pigment's color, while different nitrogen sources were not only related to pigmentation of the staining fungi, but also influenced the pigment's color remarkably.4. The influence of environmental factors on the staining fungi. Under different temperature, pH value, illumination conditions, the staining fungi were cultured, and their growth characteristics were observed. The results showed, the five staining fungi were all capable of growing in the temperature range of 10 to 35℃,and Botrydiplodia theobromae Pat. was even able to grow at 40 ℃. the optimum growth temperature was in the range of 24 to 28℃. The five staining fungi were basically able to grow on medium with pH value ranging from 2 to 11. More specifically, pH value from 3 to 8 was suitable for their growth, and the optimum pH value varied from 5 to 7. Thus, it seemed that staining fungi tended to grow favorably in acid environment. There were no obvious differences in thegrowth and pigmentation patterns for the staining fungi growing under three illumination conditions. The influence of three environmental factors on the pigmentation of the staining fungi was minor, with the exception that rapid color change and color darkening occurred under appropriate conditions.5. Infection of the staining fungi against pinus elliottii. The five staining fungi were inoculated to fresh pinus elliottii sapwood, and then the weight loss of the wood was measured. The growth of the staining fungi in the wood was observed by SEM. The results showed that, after 16 weeks of culture period, all the five staining fungi were found to cause wood weight loss, to a wide range of extent, of which, wood weight loss caused byBotrydiplodia theobromae Pat. was maximum (2.14%), followed by Trichoderma viride Pers.ex(2.04%), FusariumverticillioidesfSacc.JNireberg^.95%), Penicillium purpurogenum Stoll.(1.78%), which decreased in turn. Wood weight loss caused by Trichoderma harzianum Rifai was minimum (1.57%).The SEM observation showed the five staining fungi exhibited similar infection channels in wood structure: mycelia or conidia mainly appeared in the region of parenchyma tissue of wood structure, such as cross-field parenchyma tissue and ray parenchyma cells, going through tracheids by means of pits. Botrydiplodia theobromae Pat. grew vigorously in wood samples, resulting in big and dense mycelia, which posed the severest infection against wood parenchyma cells, followed by Fusariumverticillioides(Sacc.)Nireberg In contrast, only small and thin mycelia appeared in wood samples treated by Trichoderma viride Pers.ex, Trichoderma harzianum Rifai and Penicillium purpurogenum Stoll., in which wood parenchyma cells were hardly found to be infected.6. Chemical control of the staining fungi. Fungicidal circle and indoor antiblue stain experiments were conducted respectively to determine the inhibiting effect of 9 chemicals against the 5 staining fungi. The fungicidal circle experiment showed that, Me-TBZ, PPZwere found to have no fungicidal action, and TEB tended to demonstrate fungicidal action confined only against Fusarium helbromae Pat, Trichoderma viride Pers.ex and Penicillium purpurogenum Stoll.. Another 22 chemical formulas were all found to have fungicidal action against the five staining fungi. It also seemed that mixture for most chemicals demonstrated better fungicidal effect than single alone. Indoor anti-blue stain results showed, the fungicidal effect of the mixture of TEB and DDAC was found to be poorest, while another five chemical formulation exhibited fairly good fungicidal effect. In addition, the fungicidal effect of mixture CBZ and Cu-8, mixture of Benomyl and DDAC were slightly better than CBZ, Benomyl, Cu-8 alone.7. Biological control of the staining fungi. Soil microorganisms were employed to conduct biological control research on the five staining fungi. The results showed, three of the fungi strain were found to have antifungal action, of which, FS1-1 and GS2-2 were found to inhibit the growth of the staining fungi completely, and GS1-2 could partially inhibit it. In contrast, another nine soil microorganisms were all found to have no antifungal action.