Chaste tree(Vitex negundo var.heterophylla)witches’-broom was a new disease found in Mountain Taishan and the neighboring region.Phytoplasmal cells could be easily observed in the phloem sieve elements of diseased pl...Chaste tree(Vitex negundo var.heterophylla)witches’-broom was a new disease found in Mountain Taishan and the neighboring region.Phytoplasmal cells could be easily observed in the phloem sieve elements of diseased plants under electron microscope.The 16S rRNA gene of phytoplasma associated with this disease(CTWB)was amplified with nested-PCR with the universal primer pairs R16mF2/R16mR1 and R16F2n/R16R2.An amplified fragment of ca.1.2 kb was sequenced and subjected to identity and phylogenetic analyses.Phytoplasma CTWB shared identities of more than 99.0% with members of Aster yellows group(16SrI)in 16S rRNA genes.It had the highest identity of 99.8% with phytoplasmas associated with Maize bushy stunt(subgroup 16SrI-B),and clustered into a common branch with phytoplasmas of the subgroup in the phylogenetic tree constructed with 16S rRNA genes.These results indicated that CTWB belonged to subgroup B of Candidatus Phytoplasma asteris(16SrI-B).展开更多
在枣疯植原体16S rDNA片段内设计并合成引物对DZ16SF-2/DZ16SR-2（扩增190 bp片段）,用重组质粒pMD18-DZ16S为模板建立标准曲线,并建立枣疯植原体实时荧光定量PCR（SYBR Green I）检测体系。溶解曲线分析显示：该引物特异性好,该体系对...在枣疯植原体16S rDNA片段内设计并合成引物对DZ16SF-2/DZ16SR-2（扩增190 bp片段）,用重组质粒pMD18-DZ16S为模板建立标准曲线,并建立枣疯植原体实时荧光定量PCR（SYBR Green I）检测体系。溶解曲线分析显示：该引物特异性好,该体系对质粒模板的检测灵敏度达102 copies/μL。利用该体系对不同月份、不同发病级别的嫁接接种枣树接穗样品进行植原体含量测定。通过对高抗品种‘星光’,中抗品种‘黑腰子枣’、‘嘎嘎枣’和‘葫芦枣’,感病品种‘月光枣’、‘马牙枣’、‘莲蓬子’、‘北流西冬枣’和高感品种‘大红袍枣’嫁接到发病‘冬枣’砧木上所表现出的不同病级、病情指数和病原浓度比较结果发现,表现无症状的样品中植原体的含量在每克鲜重10^5～10^6个,发病Ⅰ～Ⅱ级枝条中植原体浓度在10^6～10^7个/g,Ⅲ～Ⅳ级发病枝条含量在10^7～10^8个/g鲜重,而V级发病枝条达到每克鲜重109个,表明接种发病的接穗症状严重度与其体内植原体浓度积累密切相关。高抗枣疯病‘星光’品种嫁接接穗体内病原浓度明显低于感病品种,而且有较多‘星光’接穗嫁接的发病砧木症状有所减轻,植原体浓度也有所降低。本研究可为探索枣树品种的抗病机制、抗病性鉴定及枣疯病植原体的防治提供参考。展开更多
文摘Chaste tree(Vitex negundo var.heterophylla)witches’-broom was a new disease found in Mountain Taishan and the neighboring region.Phytoplasmal cells could be easily observed in the phloem sieve elements of diseased plants under electron microscope.The 16S rRNA gene of phytoplasma associated with this disease(CTWB)was amplified with nested-PCR with the universal primer pairs R16mF2/R16mR1 and R16F2n/R16R2.An amplified fragment of ca.1.2 kb was sequenced and subjected to identity and phylogenetic analyses.Phytoplasma CTWB shared identities of more than 99.0% with members of Aster yellows group(16SrI)in 16S rRNA genes.It had the highest identity of 99.8% with phytoplasmas associated with Maize bushy stunt(subgroup 16SrI-B),and clustered into a common branch with phytoplasmas of the subgroup in the phylogenetic tree constructed with 16S rRNA genes.These results indicated that CTWB belonged to subgroup B of Candidatus Phytoplasma asteris(16SrI-B).
