松材线虫携带细菌的致病性

Pathogenicity of Bacteria Carried by Pine Wood Nematodes

用松材线虫携带的3种细菌(菌株Njh、菌株Njt和菌株Njw)和2种线虫(松材线虫和拟松材线虫)为接种体,以黑松愈伤组织和黑松无菌苗为接种对象,分别用无菌线虫单独接种、细菌单独接种、细菌和无菌松材线虫混合接种、细菌和无菌的拟松材线虫混合接种等,测定对黑松愈伤组织和黑松无菌苗的致病能力。接种试验结果表明,单独用无菌松材线虫或拟松材线虫接种,均不能使黑松愈伤组织褐变和无菌黑松苗枯萎,而用无菌线虫与上述3种细菌分别混合接种均能使黑松无菌苗发生枯萎及愈伤组织严重褐变。其中线虫和菌株Njh、线虫和菌株Njt致萎活性很强,线虫和菌株Njw致萎活性较弱。在自然界致病力弱的拟松材线虫与细菌混合接种同样能引起松苗严重萎蔫及愈伤组织褐变。实验室条件下,人工接种幼苗病害的发生与松材线虫携带的细菌密切相关,而与线虫的种类关系不大。松材线虫所携带的细菌在这一病害过程中起至关重要的作用。

Three bacterium strains(Njh,NJt and Njw),and two pine wood nematodes(Bursaphelenchus xylophilus and B.mucronatus) were used as inoculum.Both callus and bacteriumfree seedlings of black pine were inoculated with only bacteria,a mixture of bacteria and the aseptic nematodes of Bursaphelenchus xylophilus,a mixture of bacteria and the aseptic nematodes of B.mucronatus,etc.to determine their pathogenicity.It revealed the inoculation only with either aseptic B.xylophilus or B.mucronatus wouldn't lead to browning of the callus and wilt of aseptic black pine seedlings.But those inoculated with a mixture of the aseptic nematodes and one of the three bacteria mentioned above showed some wilting or browning symptoms.The combination of nematodes with either Njh or Njt caused severe symptoms but the combination of nematodes and Njw weak in symptom.Inoculation with a mixture of B.mucronatus which is weak in pathogenicity and the bacteria also caused serious wilt of pine seedlings and browning of the callus.It indicated that seedling symptoms under artificial inoculation in lab conditions were in a close correlation with the bacteria carried by pine wood nematodes and poorly correlated with species of nematodes.The bacteria carried by pine wood nematodes played an important role in pathogenicity.