抗病和感病泡桐无性系组培苗对嫁接传染植原体的不同反应

RESPONSES OF RESISTANT AND SUSCEPTIBLE CLONES OF \%IN VITRO\%\= CULTURED \%PAULOWNIA \%TO THE GRAFT INOCULATION WITH\= PHYTOPLASMAS

用感染了植原体并表现典型丛枝症状的组培苗作接穗或砧木，在无杂菌条件下嫁接７个表现不同田间抗性的无性系健康组培苗，并用ＤＡＰＩ荧光显微镜和１６ＳｒＲＮＡ基因扩增（ＰＣＲ）技术检验嫁接传病效果。Ｃ１２５和ＸｕＨ表现出较强的特异性接种诱发坏死反应，ＺＨ和Ｔ３５０２８坏死反应中等，ＱＬＭ、Ｃ０２０和Ｃ１６１的坏死反应较弱。培养基中添加植物生长调节剂（６ＢＡ或ＮＡＡ）可降低坏死程度，提高嫁接成功率，水杨酸处理或去掉健株砧木叶片和根系皆加重坏死反应程度。用病接穗嫁接抗病的ＱＬＭ无性系时，用ＰＣＲ检测到侵染砧木的植原体，但未表现丛枝症状，而将此无性系健康接穗嫁接到丛枝病砧木上时可诱致典型丛枝症状，从而表现出与根系和成熟叶相关的抗性反应。除Ｃ１２５外，其余６个无性系皆被嫁接传染，其继代培养表现出差异不显著的丛枝症状，其韧皮部金黄色自发荧光随着症状的加重而累积，也与抗病性有一定的联系。

The graft tests were performed under the sterile and \%in vitro \%cultured conditions using infected plantlets with phytoplasmas and seven phytoplasma\|free clones of \%Paulownia \%spp. displaying different degrees of natural resistance. DAPI fluorescence microscopy and polymerase chain reaction(PCR) based on the phytoplasma 16S rRNA gene sequence were taken for the pathogen detection. The result indicates that the graft transmission of phytoplasma from diseased scion to healthy rootstock or from diseased rootstock to the healthy scion is a new efficient way to evaluate the resistance of \%Paulownia \%against phytoplasmas as well as to acquire infected clone materials. The clone C125 and XuH demonstrated strong necrotic reaction along the stem of the inoculated rootstocks from graft joints, ZH and T35\|028 with moderate degree of necrosis, while QLM, C020 and C161 with slight reaction. Plant growth regulators(6\|BA,NAA) added to MS medium reduced the necrotic effects, therefore increasing graft efficiency, while salicylic acid(SA) in the medium, or the removal of the roots and leaves from inoculated rootstock aggravated it. The reliable graft of diseased scion on QLM rootstock showing natural resistance did not induce witches' broom symptoms on QLM rootstock, despite the fact that pathogens were detected in the grafted rootstock plantlets by PCR. However, by grafting healthy QLM shoot on diseased rootstock, QLM scion was likely to develop typical witches' broom symptoms, which indicates some correlated resistance with that of roots or mature leaves. The phytoplasmas were graft\|transmitted into all clones, except C125, and induced indistinguishable witches' broom symptoms to one another. In the phloem of infected tissues of each clone, the bright autofluorescence accumulated gradually, with the development of symptoms; and the intensity of the autofluorescence was correlated with clone's resistance to some extent