Yu Shao-Shuai, Zhu An-Na, Song Wei-Wei, Yan Wei
Coconut Research Institute, Chinese Academy of Tropical Agricultural Sciences, Wenchang 571339, China.
College of Forestry, Hainan University, Haikou 570228, China.
Biology (Basel). 2022 Jun 6;11(6):869. doi: 10.3390/biology11060869.
The pathogens associated with citrus Huanglongbing symptoms, including yellowing and mottled leaves in , an important economic crop on Hainan Island of China, were identified and characterized. In the study, detection, genetic variation and phylogenetic relationship analysis of the pathogens were performed based on 16S rRNA and β-operon gene fragments specific to phytoplasma and Liberibacter asiaticus. The results indicated that the pathogens-such as phytoplasma strains of CmPII-hn belonging to the 16SrII-V subgroup and CmPXXXII-hn belonging to the 16SrXXXII-D subgroup, as well as Liberibacter asiaticus strains CmLas-hn-were identified in the diseased plant samples, with numbers of 12, 2 and 6 out of 54, respectively. Among them, mixed infection with the 16SrII-V subgroup phytoplasma and Liberibacter asiaticus was found in the study, accounting for 7.4% (four samples). The phytoplasma strains of CmPII-hn- witches' broom, witches' broom and witches' broom-were clustered into one clade belonging to the 16SrII-V subgroup, with a 99% bootstrap value. The phytoplasma strains of CmPXXXII-hn and witches' broom belonging to 16SrXXXII-D, and the other 16SrXXXII subgroup strains were clustered into one clade belonging to the 16SrXXXII group with a 99% bootstrap value. There were 16 variable loci in the 16S rRNA gene sequences of the tested 16SrXXXII group phytoplasma strains, of which two bases had an insertion/deletion. The strains of Liberibacter asiaticus, identified in the study and the strains that had been deposited in GenBank, were in one independent cluster with a 99% bootstrap value. To our knowledge, this is the first report showing that can be infected by 16SrII-V and16SrXXXII-D subgroup phytoplasmas in China. Moreover, this is also the first report in which the plants are co-infected by 16SrII-V subgroup phytoplasmas and Liberibacter asiaticus. More comprehensive and detailed identification and characterization of the pathogens associated with the diseased symptoms in on the island in China would be beneficial for epidemic monitoring and for the effective prevention and control of related plant diseases.
对与中国海南岛重要经济作物柑橘黄龙病症状（包括叶片黄化和斑驳）相关的病原体进行了鉴定和特征分析。在该研究中，基于植原体和亚洲韧皮杆菌特异的16S rRNA和β-操纵子基因片段，对病原体进行了检测、遗传变异和系统发育关系分析。结果表明，在患病植物样本中鉴定出了病原体，如属于16SrII-V亚组的CmPII-hn植原体菌株、属于16SrXXXII-D亚组的CmPXXXII-hn植原体菌株以及亚洲韧皮杆菌菌株CmLas-hn，在54个样本中分别有12个、2个和6个。其中，研究发现16SrII-V亚组植原体与亚洲韧皮杆菌混合感染，占7.4%（4个样本）。CmPII-hn-扫帚病、扫帚病和扫帚病的植原体菌株聚为一个属于16SrII-V亚组的分支，自展值为99%。属于16SrXXXII-D的CmPXXXII-hn植原体菌株和扫帚病植原体菌株，以及其他16SrXXXII亚组菌株聚为一个属于16SrXXXII组的分支，自展值为99%。所检测的16SrXXXII组植原体菌株的16S rRNA基因序列中有16个可变位点，其中两个碱基存在插入/缺失。本研究鉴定的亚洲韧皮杆菌菌株与已存入GenBank的菌株聚为一个独立分支，自展值为99%。据我们所知，这是中国首次报道柑橘可被16SrII-V和16SrXXXII-D亚组植原体感染。此外，这也是首次报道植物被16SrII-V亚组植原体和亚洲韧皮杆菌共同感染。对中国该岛上柑橘患病症状相关病原体进行更全面、详细的鉴定和特征分析，将有助于疫情监测以及相关植物病害的有效防控。
