【作者】 苏静；

【导师】 马青；

【作者基本信息】 西北农林科技大学 ， 植物病理学， 2007， 硕士

【摘要】 苹果斑点落叶病(Alternaria alternata f. sp. mali)已经成为我国苹果生产上的重要病害,在我国大部分苹果产区均有发生,严重影响苹果产量和品质。本研究通过分离、筛选对苹果斑点落叶病具有拮抗作用的菌株,并且对拮抗菌株的特性进行研究。主要结果如下:从苹果树的不同部位分离获得内生细菌118株,在苹果不同生长季节以及不同部位分离获得的内生细菌数量不同。叶片中内生细菌数最多,达到4.95×102 cfu/g,树皮中的内生细菌数量居中,为4.4×10~2cfu/g,茎中存在的细菌数最少,为1.83×10~2 cfu/g。从叶片上分离到的细菌种数占所分离内生细菌总种类的75%。通过平板对峙培养和发酵液抑菌活性测定,在所分离的118个菌株中,筛选出7株对苹果斑点落叶病菌具有较强拮抗作用的菌株,其中菌株B86和B91的发酵滤液在活体上对苹果斑点落叶病的防治效果显著,其防效分别为73.72%和75.32%。B86和B91两菌株培养滤液对斑点落叶病菌的分生孢子萌发具有较强抑制作用,用培养滤液原液处理的分生孢子萌发率最低,分别为8.7%和6.7%,并造成芽管畸形膨大,呈泡囊状,泡囊逐渐消解破裂,分生孢子萌发受到完全抑制。两菌株对14种病原真菌菌丝生长均具有较好的拮抗作用,表明两菌株具有较广的抗菌谱。两菌株培养滤液抑菌活性在50℃至90℃范围内具有热稳定性。两菌株培养滤液在pH6.0-7.0时抑菌活性最高,pH5.0-9.0范围内其抑菌物质具有酸碱稳定性。随着酸、碱性不断增加,抑菌活性逐渐下降。两菌株最适生长条件测定表明,菌株B86和B91培养生长的最适初始pH值分别为pH6.0和pH7.0;菌株B86和B91的最适生长温度分别为28℃和30℃。更多还原

【Abstract】 The apple spot leaf drop disease, Alternaria alternata f.sp. mali, has become a serious disease in most apple growing areas of China by decreasing the output and quality of apple. The objectives of this research are to isolate and screen effective antagonistic endophytic bacteria against this disease and to study the characteristic of the antagonistic strains. The main results are as follows:One hundred and eighteen strains of endophytic bacteria were isolated from various organs of apple trees and in various growing seasons. The amount of endophytic bacteria separated from leaves is the greatest, reaching 4.95×102 cfu/g, followed by the bark, 4.4×102cfu/g, with the stem in the least, 1.83×102 cfu/g. The endophytic bacteria from leaves accounts for 75%.The result demonstrated that 7 strains of endophytes showed strong antagonistic activities to the pathogen by dual-culture tests, in which strains B86 and B91 had the strongest antagonistic effect through inhibitory activity test. Their fermentation filtrates had inhibitory rates to the pathogen as 73.72% and 75.32%, respectively.Fermentation filtrates of B86 and B91 had strong inhibition to spore germination of the pathogen, with germination rate of 8.7% and 6.7%, respectively. Deformation and disintegration of spore germ tubes were observed in the treatment of filtrates. Two strains had better antagonism to 14 different kinds of pathogenic fungi, indicating that two strains had broader antibiosis range.The antifungal compounds of two strains were stable to the heat treatment between 50℃and 90℃, and between pH5.0 and pH9.0. The rates of inhibition of B86 and B91 were the highest at pH6.0 and pH7.0, but declined when acidity and basicity are respectively strengthened.The results of optimal culture conditions showed that the optimal initial culture pH value of B86 and B91 are pH 6.0 and pH7.0, respectively. The growth of the strains is restrained in strong . The optimal culture temperature of two strains is 28℃and 30℃, respectively.更多还原