三叶草、豌豆和快生型大豆根瘤菌类菌体繁殖研究的进展

ADVANCES OF STUDIES ON BACTEROID REPRODUCTION OF R.trifolii,Rhizobium leguminosarum, AND FAST-GROWING SOYBEAN RHIZOBIUM

采用单个原生质体分离和微室培养技术研究了三叶草、豌豆和快生型大豆根瘤菌在根瘤中的分化和繁殖。结果表明:快生型大豆根瘤菌体的分化和繁殖特性与慢生型大豆根瘤菌类似,多个杆状类茵体包含在一个共同的类菌体周膜中,可区分出未成熟的细小杆状类菌体和成熟的杆状类菌体;其繁殖率在刚现瘤时<0.01％,到10周瘤龄时增加到40％以上。而三叶草和豌豆根瘤菌在根瘤中的分化过程是从小杆菌→未成熟细长杆状类菌体→成熟的棒状或Y状类菌体。在一般条件下,只有小杆菌才能繁殖,其繁殖率也随瘤龄而增加。在根瘤发育后期,少数成熟的三叶草和豌豆根瘤类菌体,在含水量较多时,可以转化为活跃运动的大杆菌,然后在分裂过程中逐次缩小并最终转变为正常的根瘤小杆菌;含水量较少时,大杆菌继续生长形成假丝状体,最后再断裂为大杆菌或停止生长。渗透压保护不是根瘤类菌体或小杆菌繁殖的必要条件,除对幼小根瘤的未成熟类菌体外,它妨碍成熟类菌体或小杆菌的生长和繁殖。

The reproductivity of bacteroids from soybean ( with R.fredii USDA 192) , pea ( with R. legvminosarum 300 ) and white clover ( with R, trifolii T1) was tested by protoplast isolation and crushed nodule solution with the comparison of viable and total counts.The growth process was record ed by microchamber incubation and video recording. The morphology of bacteroids was rod ( for soybean ) or club and Y shape ( for pea and clover).Only rod shaped bacteroids ( soybean ) and small rods(pea and clover) showed growth and their reproductivity increased with the age of nodules (for soybean:from 0.01% at first nodule appearance to 40% at 10 weeks; for pea: from 0.01% at 2 weeks to 13% at 8 weeks). Osmoprotection showed no benefcial effect except for the young nodules. Bacteroids and small rods released from single protoplasts showed the same growth curve, but their absolute value was much lower that those from crushed nodules.A few bacteroids from old pea and clover nodules showed growth in microchamber incubation. They changed first to large motile rods and then started to divide.The width of rods got smaller after each division and finally reached the same size as rhizobia.The abnormal growth of pea bacteroids was also found when the moisture of growth chamber was low. They could change to the filament-like structure and broke into large rods or stoped to grow.