Abstract: In order to further investigate the biological characteristics of root rot pathogens and the pathogenicity of different pathogens to alfalfa,three root rot pathogens including BF1(Fusarium equiseti),BF28(F.oxysporum) and BF36-2(F.solani) were selected as experimental materials to investigate their bio-characteristics and reproductive capacities.Four alfalfa varieties of WL343,Golden Empress,Algonguin and WL525 were inoculated by fungal suspension and fungal cakes.The results showed that alfalfa was effected more rapidly and more severely by using fungal suspension in compared with using fungal cakes.Different strains had different colonization abilities in alfalfa root system.The mycelium of BF1 gathered near the roots,but that of BF28 and BF36-2 did not gather.In the form of bacterial cake inoculation,the pathogenicity of three strains was different.The strains with strong sporulation ability had strong pathogenicity.The pathogenicity of BF28 was the strongest,followed by BF36-2,and BF1 was the weakest.Infection process and interaction access between host plant and Fusarium were studied through anatomical structure.Pathogens invaded into epidermal cell with chlamydospores.They spread in the intercellular in the form of myclium or spores.Spores released toxin that dissolving the cell wall and decaying the host tissue in finally,root pulp became hollow and the leaves appeared ulcerative spots,plant growth was hindered.

Key words: Alfalfa varieties, Fusarium, Root rot, biological characteristics

摘要： 为了进一步了解根腐病病原菌的生物学特性以及不同病原菌对苜蓿的致病性,本研究以苜蓿根腐病病原BF1(Fusarium equiseti)、BF28(F.oxysporum)、BF36-2(F.solani)三种镰孢菌菌株为试验材料,观测菌落的外观特征与产孢量,并对WL343、金皇后、阿尔冈金、WL525四个苜蓿品种以菌液和菌饼两种方式接种,比较不同菌株对苜蓿的致病性。结果表明,菌液接种方式,苜蓿感病较快,感病程度较重。不同菌株在苜蓿根系的定植能力不同,BF1菌丝在根系附近聚集;而BF28及BF36-2菌丝则均匀分布于培养基表面。菌饼接种方式,不同菌株对苜蓿的致病性存在较大差异,产孢能力强的菌株致病力强。BF28对苜蓿的致病性最强,BF36-2次之,而BF1的致病性较弱。通过对感病植株进行解剖构造与致病过程观察,病菌以厚垣孢子入侵根系及叶片表皮细胞,以菌丝体及孢子形式在细胞间隙扩展,并向植物组织中释放细胞壁溶解物质,植物细胞壁溶解,根髓部腐烂中空,根颈部缢缩,叶部出现溃烂斑,植株的生长受阻。

关键词: 紫花苜蓿, 镰孢菌, 根腐病, 生物学特性