不同宿主植物根瘤Frankia及其生物学特性

对从木麻黄、杨梅、桤木和胡颓子等宿主植物根瘤中获得的19株分离菌的离体培养形态特征、生理特性和交叉侵染特性等进行了比较分析.结果表明,各分离菌均有Frankia属所特有的分枝状菌丝、孢囊、泡囊或串珠状菌丝等形态结构;细胞壁类型多属胞壁Ⅲ型,生理类型多属B型,无氮诱导培养下都具有同氮酶活性,在BAP、JA或S培养液中菌体生长较好,以吐温-80和酪蛋白水解物为最佳碳、氮源.但不同宿主分离菌的形态和培养特征差异明显,木麻黄属分离菌菌丝较粗,孢囊数量较少,在BAP培养液中多旱荔肉白絮状颗粒沉淀;杨梅属菌丝较细,孢囊数量较多,在BAP培养液中多是浅红色颗粒沉淀;桤木属和胡颓子属的菌体形态特征在BAP培养液中与木麻黄属的相似,但桤木属菌丝较细,胡颓子属的菌丝较粗.根据回接及交叉侵染特性可将分离菌分为2个宿主特异类群:能侵染木麻黄苗木的木麻黄类群;只侵染原宿主并能在杨梅属、胡颓子属和桤木属间相互侵染,但不能使木麻黄属苗木结瘤的杨梅-桤木-胡颓子类群.图2表5参19

Biological Characteristics of Frankia Isolated from Different Actinorhizai Plants

19 strains were isolated from the root nodules of actinorhizal plants Casuarina, Myrica, Elaeagnus and Alnus by squashing, and their morphological, physiological and cross-infection characteristics were studied. The results showed that all the isolates had a typical Frankia morphology with filamentous hyphae, sporangia and vesicle. The reproducrive torulose hyphae were observed in some isolates (FCc64, FCe33 and FMr43). Most of the Frankia isolates were characterized in that their cell walls were type Ⅲ and the physiological groups belonged to B. Furthermore, it is deduced that these strains all had nitrogenase activity for their growth in the nitrogen-free medium. They were also found growing well in liquid media BAP, JA and S. Tween-80 and casein were the optimum carbon and nitrogen sources. However, some obvious differences in morphological and cultural characteristics occurred among the strains isolated from different actinorhizal plants. Most of the isolates from Casuarina had thick hyphae and few sporangia, and formed Lichee's meat white flocculent granular precipitate in the BAP liquid medium, while most of the isolates from Myrica rubra had thin hyphae and many sporangia, and formed rosiness granular precipitate. The morphological characteristics of the isolates from Alnus and Elaeagnus were similar to the isolates from Casuarina in the same medium, but the isolates from Alnus had thin hyphae while the isolates from Elaeagnus had thick hyphae. The Frankia isolates were divided into two host-specific groups, according to back inoculation experiment and cross-infection of pure culture with seedlings of Casuarina cunninghamiana, C. equisetifolia, C. glauca, Myrica rubra, Alnus cremastogym and Elaeagnus angustifolia. The strains of group Ⅰ which were all isolated from Casuarina could not only infect Casuarina, but also Myrica, Elaeagnus and Alnus, and those of group Ⅱ from Myrica, Elaeagnus and Alnus had the ability to infect the unoriginal host plants except Casuarina. Fig 2, Tab 5, Ref 19