| Betula platyphylla Suk is the main forest culture & management and timber tree species, however its stain degrades the wood products, which leads severe economic loss to wood industry. Therefore, the objective of this dissertation is to meet Betula platyphylla Suk's stain principle, eliminate stain hidden trouble, and reduce economic loss efficiently. The contents mainly include: study on wood stain mechanism and selection of the antimicrobial strain to biologically control stain fungi. The main results are as follows:[1] The study on Betula platyphylla Suk wood stain mechanism shows that, the main blue stain was caused by sapstain fungi, and brown stain occurred in small scope by physiological protection. The changing of L*, a*, b* andΔE* indicated, the blue-stain wood colour darkened wholly, but brown-stain wood colour didn't change except the small stain scope.[2] The contents of blue-stain wood extractives by cold water, hot water, 1%NaOH and alcohol benzene were higher than healthy wood, and pentosan content was less, but cellulose and lignin contents didn't change. Therefore sapstain fungi just dissolved hemicellulose.[3] Comparing with healthy Betula platyphylla Suk, the cellulose, pentosan and lignin contents of brown-stain wood held the line. Namely the main components weren't destroyed.[4] Five sapstain fungi were isolated from stain tissues of Betula platyphylla Suk. They were Alternaria alternata (Fr.) Keissl, Graphium sp., Trichoderna viride Pers. ex Fr., Ceratocystis fimbriata Ell. et Hals and Botryodiplodia theobromae Pat Griffon & Maubl.[5] Alternaria alternate could grow at the temperature from 10℃to 35℃, and the optimum temperature was 25℃. When the temperature was lower than 5℃or higher than 40℃, it couldn't grow. The suitable pH for its growth was in weak acid system. The growth rate was the highest in 24-hour-illuminated condition. [6] Growth of Graphium sp. is the fastest at 30℃, and grew slowly at 10℃, 15℃. when the temperature was lower than 5℃or higher than 40℃, it couldn't grow. The pH value had little effect on its growth. The growth rate was the highest in natural lighting condition.[7] Trichoderna viride could grow at the temperature from 10℃to 35℃. The optimum temperature was 25℃. when the temperature was lower than 5℃or higher than 40℃, it couldn't grow. The pH value and illumination condition had little effect on its growth.[8] Ceratocystis fimbriata could grow at the temperature from 10℃to 35℃. and the optimum temperature was 25℃. when the temperature was lower than 5℃or higher than 40℃, it couldn't grow. The pH value and illumination condition had important effect on its growth, and the optimum pH value, illumination were pH7, 24-hour-illuminated condition.[9] Botryodiplodia theobromae could grow at the temperature from 10℃to 35℃. and the optimum temperature was 30℃. when the temperature was lower than 5℃, it couldn't grow. The pH value and illumination condition had little effect on its growth.[10] 129 test strains including 98 actinomyces and 31 bacteria for antimicrobial strain were isolated from Betula platyphylla Suk tissue and soil in situ. 36 actinomyces and 6 bacteria were identified as antimicrobial strains on the improved PDA culture, among which B26 had the strongest antimicrobial activity to the five sapstain fungi. The strain was identified as Bacillus Subtilis according to its morphology, physiological & biochemistry characters and analyse of 16SrDNA after isolated and cultured.[11] The growth of Bacillus sp.B26 strain grew better with the temperature increase before 35℃. The growth and antimicrobial activity of Bacillus sp.B26 strain were restrained in acid or alkali system.[12] The metabolite of Bacillus sp.B26 had good ability to temperature and pH. Its antimicrobial activity had effect under 85℃, and it could keep favorable activity from pH1~pH13 especially in acid system, which made it have potential adapting ability to the weak acid environment of Betula platyphylla Suk wood.[13] The metabolite of Bacillus sp.B26 had good ability to temperature, pH value, enzyme, illumination condition and keeping time, which were the excellent characteristics for exploring biological control products.
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